The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
The very first Google hit for "Smardale bridge" shows a photo of the bridge, with the caption "Smardale Bridge crosses Smardale Gill.... Behind the bridge are 'Giants' Graves,' archaeological features of uncertain origin that date to prehistoric times." There are lots more links beside. Looie496 (talk) 05:45, 26 July 2010 (UTC)[reply]
No.No. You misunderstand, I know where it is. My question is: why is/what is it geologically important and how can I find more about the geological features that are important. Sf5xeplus (talk) 11:23, 26 July 2010 (UTC)[reply]
I think your best bet is to simply ask the Cumbria RIGS Group what the criteria for the listing were (there's a "Contact us" link at the bottom of the page). Alternatively, since the group says that "site details are logged with local authorities and the County Council", you might try the county council. Deor (talk) 15:58, 26 July 2010 (UTC)[reply]
Many (most?) gay males don't exhibit any more effeminacy than straight males do. Many gay males gravitate towards the hyper-masculine, others might be 'bears', others don't behave any different from anybody else. It's largely a social thing, mixed with whatever makes the person comfortable. So if we narrow your question down to "what causes effeminacy in the small percentage of gay males who exhibit a marked tendency towards effeminacy?", then Cuddlyable3 and LarryMac's answers have it covered. 76.105.238.158 (talk) 00:32, 27 July 2010 (UTC)[reply]
They purposely do that so people know their gay. there is no other explanation.--Horseluv10 11:55, 27 July 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)
Why do straight effiminate males do it then? And why don't the other gay males bother? And why do some gay effiminate males stay in the closet for so long? And what's wrong with the plenty of other explainations like the ones above? Nil Einne (talk) 21:34, 27 July 2010 (UTC)[reply]
What possible meaningful scientific answer do you imagine you could get for the above questions? Ask your self why YOU behave the way you behave? Why you are attracted to (presumably) girls instead of boys? If you can come up with a more meaningful answer then "because they're hot", and you aren't allowed to cheat by saying "millions of years of evolution" because that's something you are told by others, I'm sure you aren't thinking "I'm sure glad evolution has made me attracted to girls so we can have lots of offspring" when you admire someone you fancy. Human behavior is probably one of the most complex subjects you can study and people spend lifetimes trying to understand and explain it, often getting it totally wrong. It doesn't help that there are a LOT of errors and misconceptions in "common wisdom" about psychology. Vespine (talk) 23:30, 27 July 2010 (UTC)[reply]
Yeah that makes more sense reading it again, sorry my rhetorical detector wasn't functioning correctly.. It's precisely that dogma around this subject that frustrates me, perhaps a little too quickly. Part of the reason for that is Nil's questions would NOT be the most ignorant questions I've ever heard about sexual preference if he had been serious.Vespine (talk) 05:00, 28 July 2010 (UTC)[reply]
Yeah 86 is correct. No problem about the confusion since as you may have guessed I too dislike silly statements about sexuality. You are correct that I'm heterosexual in any case. Nil Einne (talk) 09:53, 28 July 2010 (UTC)[reply]
This isn't a comment on your statement, just an interesting thought I've had, that when I answer people who "question" homosexuality I honestly have to fight the urge to say that I'm hetrosexual, because I can almost feel the people on the other end thinking "oh he's probably gay". But I know pointing out I'm hetro won't change their opinion anyway so unless they ask I make it a point not to mention it. (I know that's not what you were doing).. The funny part is that I think there is a real similarity to racism, now there is such a stigma around racism that I don't even feel comfortable drawing that analogy but maybe that's more reason to do so. I NEVER feel the need to point out that I'm white, I believe one day we'll live in a world when no one feels the need to point out they are hetro. Imagine these days someone asking what it "feels like" to be black, as if it is "different" from being a normal human. Unfortunately there are stsill many people who feel this way about homosexuals, but I also believe they are a dying breed. Vespine (talk) 00:03, 29 July 2010 (UTC)[reply]
One scientific paper which I read suggested the idea that there are many (epi)genetic factors which contribute to the "feminine" (gentle?) traits of the male and that the ownership of some of these factors make their benefactor a better mate by ensuring an appropriate response to their fragile partner and offspring. Since our reproductive systems rely on random homologous recombination, it possible that in some cases, an individual inherits more or less of these characteristics than average and as a result become overly masculine or overly feminine for optimum reproductive value. On top of this however, you have the confounding environmental (including cultural) aspects already alluded to above. --SeansPotato Business23:00, 28 July 2010 (UTC)[reply]
A 100 W light bulb emits light with a wavelength of 575 nm
How many photons leave the filament of the globe in 1 second?
Basically I have no idea how to do the question. I can convert the wavelength to frequency and then I can convert that to energy if that helps --220.253.172.214 (talk) 10:10, 26 July 2010 (UTC)[reply]
I think this is just a homework question ;) You're right that the situation is not physically realistic, but the same goes for many such problems. Physchim62(talk)10:35, 26 July 2010 (UTC)[reply]
Don't leave out the units! Besides being a requirement for physics calculations, making sure the units match is an excellent way of checking that your calculations are right. (In many cases if you don't know the formula, simply making the units correct will automatically give you the correct formula. This doesn't always work, but it works often enough to be a good first try for an unknown calculation.) Ariel. (talk) 13:47, 26 July 2010 (UTC)[reply]
There's some basic figures at the bottom of this page [1] , other sources quote a figure of 10-20% of total weight (presumably for a non obese person).This [2] gives 13% of body weight. 87.102.43.171 (talk) 13:39, 26 July 2010 (UTC)[reply]
Living human, or dry bones? (Not that I know the answer, but there is a large weight difference between the two.) Ariel. (talk) 13:49, 26 July 2010 (UTC)[reply]
I'm talking about the objects that make up quarks, not the things you use to tie your shoe with. Since they are 1 dimensional structures, it made me think if they are really matter or energy. Of course I'm aware that matter and energy are related (E=mc2) but, is it fair to say that the line is kind of blurred at that level? 148.168.127.10 (talk) 14:04, 26 July 2010 (UTC)[reply]
First of all, it is important to note that string theory doesn't have any significant evidence in favour of it (so it's a bit of a stretch to even call it a theory, it's just an idea). Assuming string theory is correct, then it doesn't really make sense to distinguish between matter and energy at the scale of individual strings. Photons are made out of strings in the same way quarks are and there isn't really any difference between those strings other than the way they vibrate. --Tango (talk) 14:35, 26 July 2010 (UTC)[reply]
What determines wether the particle has mass is the vibrational pattern of the string, not the string having mass itself, for example a photon is massless because it has a different vibration than quarks do even though they are both 1 dimensional vibrating strings according to string theory.--74.67.89.61 (talk) 14:50, 26 July 2010 (UTC)[reply]
Just to comment on the distinction between matter and energy: One shouldn't say that "something is energy" as if energy were something material or substantial; it is not. The correct way to put it is "Matter has energy", and the (misnomed) equivalence between matter and energy means that matter has energy even when it is at rest. So photons and strings will have energy, but they are not energy. Whether you want to call photons and strings "matter" depends on whether you want matter to be made of particles with mass or whether you accept massless particles, too. --Wrongfilter (talk) 10:02, 27 July 2010 (UTC)[reply]
Oh sure, I know about that. I just meant within the context of what he was saying. I suppose we can't call any object energy then. Photon is not matter or energy, but it has energy. What about the four fundamental forces? Can we call any of those energy? 148.168.127.10 (talk) 15:53, 27 July 2010 (UTC)[reply]
Actually photons ARE energy. So is mass - mass does not contain energy - it is energy (and energy is mass, they are not just interconvertable they are two words for the same thing, but each has a different emphasis). The forces are not energy, but they do transmit energy, so while in transit they could contain energy. Ariel. (talk) 01:25, 28 July 2010 (UTC)[reply]
If they were the same thing, then we could simply throw out one of the terms and only use the other; much more economical. No, conceptually, mass and energy are very different things. Mass (that is rest mass) is an intrinsic, unchangeable property of a material particle; as such, mass is independent of the frame of reference. Energy is a quantity that describes the state (of motion, for instance) of a particle or physical system. It is a mathematical function that has properties which make it extremely useful to describe the state and behaviour of real physical systems; and energy depends on which frame of reference you choose. --Wrongfilter (talk) 09:41, 29 July 2010 (UTC)[reply]
That is incorrect. Mass also depends on the frame of reference, and energy might be invariant. For example chemical energy, or potential nuclear binding energy (the energy that the sun releases) are both invariant, and they show up as mass of course, even though they are "energy". Temperature and electric charge are also invariant (yes electric charge is energy - potential energy). Actually the only that is not invariable is kinetic energy. As you drill down you will find there is no intrinsic mass - all the mass is actually the result of potential energy of one kind or another. There is a reason that particles are weighed in electron volts (supposedly a measure of energy) instead of grams. Mass and energy are the exact same thing, and the only reason we use two words is historical. And now that we have two words we give them different emphasis. Ariel. (talk) 16:04, 29 July 2010 (UTC)[reply]
We could probably go on for a long time, so this'll be my last comment. Mass: Note that I referred to rest mass as the intrinsic property of a particle. Rest mass is the invariant length of four-momentum (the time component of which is energy - making it very clear from a mathematical point of view that energy and mass are different things). Temperature: When measuring temperature one doesn't take into account centre-of-mass motion. This is of course irrelevant because and entropy doesn't depend on bulk motion (and vice versa). Chemical/binding energy: You seem to suggest that I dispute the validity of E=mc2 - of course I am not. But that equation doesn't imply that the two are identical concepts. I would like to see a reference for your claim that "electric charge is energy". I would also like to see a reference for the claim that "mass is ... the result of potential energy" - have you solved the problem of the origin of mass? --Wrongfilter (talk) 17:53, 29 July 2010 (UTC)[reply]
soundwaves
Is it possible to view a soundwave in 3D? So for example would it be possible to develop a software that shows a soundwave from front on? —Preceding unsigned comment added by 91.103.185.230 (talk) 15:51, 26 July 2010 (UTC)[reply]
You could have software that shows 2d sections through a soundwave. More complicated solutions could include using transparent colour or exaggerated refractive index to visualise the soundwave. However note that high frequency sounds have short wave lengths eg 3.3kHz has only a 10cm wavelength. The problem with 3d visualisation of room full of soundwaves is that it would be looking through fog - also from front on you would be looking through pressure wave peaks and troughs - as the sound wave propagates itself there would be very little or no difference over time in the appearance (from front on). 87.102.43.171 (talk) 16:28, 26 July 2010 (UTC)[reply]
Showing 'isobars' of soundpressure level would be a lot easier - again using transparent (coloured) surfaces to visualise the sound level at different positions in space.87.102.43.171 (talk) 16:31, 26 July 2010 (UTC)[reply]
We regularly encounter this problem during full wave equation modeling for seismic imaging. (I'm sure RADARs and SONARs could have similar visualizations, but their data is less commonly visualized in a full 3D sense - in seismic imaging, the final desired result is a visualization of the entirety of a 3D volume, including its interior). Because the 3D wavefront is, well, three-dimensional, trying to render it on a 2D screen means you have to makes some tradeoffs. Many options exist for displaying the actual wavefront - you can pick an isosurface (i.e., interpolate one surface such that each point (X,Y,Z) has the same acoustic amplitude or phase) and render it in 3D; you can render a cube, and use a unique user-interface to select planar cross-section views; you can render an animated movie that traverses through one or more axes. Or, you can process the results of the acoustic wave, and instead of visualizing the wavefront, you can image some derived parameter - e.g. reverse time migration, where the results are correlations of the acoustic wavefront with a time-reversed version of the recorded echos. You can visualize the 3D acoustic wavefront in the fourier domain, or some other transform domain, where its 3D characteristics collapse along one or more dimensions. Every one of these approaches comes with difficult tradeoffs that boil down to, ultimately, you can't completely represent a complicated 3D structure on a 2D viewing screen. We have some peripherally related articles, volume rendering, tomography, and so on, that explain the difficulty of imaging a 3D structure. Nimur (talk) 20:15, 26 July 2010 (UTC)[reply]
Thermodynamics what-if
You have a box made out of a material which is very rigid and has a low thermal expansion coefficient. It is filled to the brim with water at room temperature. Suddenly you thrust it out of the airlock of your spaceship into the vacuum of space which is a couple of degrees above absolute zero. Because the box material conducts heat, the heat energy of the water leaves through the box and the water starts to cool down. When the temperature of the water gets to the freezing point, since water is one of the different materials that is less dense as a solid than it is as a liquid, the water begins to be under pressure as it pushes on the box. Say the box held rigid. It seems to me this pressure would have an effect of increasing the water temperature so it would go back to liquid. So would the water in the box in that frigid environment stay liquid or form some denser-than-normal ice? 20.137.18.50 (talk) 16:35, 26 July 2010 (UTC)[reply]
It would stay liquid for longer, i.e. at a lower temperature, but eventually it would still freeze. Keep in mind that the lower density of ice is only around the freezing point. Eventually it starts contracting like other materials, this article suggests that that temperature is 200K (about -70c) - see the graph. But keep in mind this graph was made at ambient pressure. Inside your box the pressure will be much higher which will influence things. Ariel. (talk) 16:48, 26 July 2010 (UTC)[reply]
Freezing point doesn't vary much with pressure (unlike boiling point), so it wouldn't stay liquid at a significantly lower temperature. --Tango (talk) 17:02, 26 July 2010 (UTC)[reply]
If you increase the pressure on a gas, it warms up, but I'm not sure the same is true of a liquid. Liquids are pretty much incompressible, so I don't think they would change temperature much. Regardless, as Ariel says, the water would eventually cool to the point where ice is denser than liquid water, at which point it would definitely freeze. --Tango (talk) 17:02, 26 July 2010 (UTC)[reply]
At equilibrium, the pressure inside the box will be lower than when you started, because the density of (normal) ice is higher than that of liquid water at low temperatures. While the water is cooling down, the pressure will be very much higher (but I'm assuming you want us to consider an infinitely rigid box). Physchim62(talk)17:15, 26 July 2010 (UTC)[reply]
I think I need to slightly correct what Tango said above - freezing point does change with pressure for materials like water that change volume on freezing. Since water initially expands on freezing increased pressure lowers the freezing point (described in general by Le Chatelier's principle) .. Since both water and ice are very incompressible even a small amount of (normal) ice formation would cause a very massive increase in pressure.
There are denser forms of ice - I don't know if the conditions here would be sufficient to cause its formation over normal ice - though I would guess it's likely.87.102.43.171 (talk) 17:34, 26 July 2010 (UTC)[reply]
Generic phase diagram - the dashed green line shows water, the solid green line shows typical substances. This phase diagram seems to show that the freezing point of water changes less with changes of pressure than typical substances (although water does at least change in the right direction). Both the solid and dashed green lines are pretty close to vertical, so the change is pretty small. --Tango (talk) 18:08, 26 July 2010 (UTC)[reply]
water expands about 10% on freezing, the bulk modulus of ice is ~1010Pa - so to compress ice to the same volume of water would require about 1000MPa of pressure. In fact this is beyond the pressure for which normal ice exists - so one of the more dense forms of ice is formed. There's a similar discussion (from which I got the compressability data from) here [3]
The same link references this page [4] which has a phase diagram which extends beyond that given right - It looks like ice V or VI would be formed at 0C at these pressures. However if the cooling was rapidly to 0K and not 0C all this is not relavent.87.102.43.171 (talk) 19:34, 26 July 2010 (UTC)[reply]
I got a very rough figure of 1degree change in freezing point per MPa (ie 0.1 degree C per bar/atmosphere) - no idea how accurate that is.87.102.43.171 (talk) 20:44, 26 July 2010 (UTC)[reply]
That will only be accurate near a specific temperature (probably 0 deg C). It can't be accurate everywhere, otherwise the freezing point at 300MPa would be below absolute zero, which is obviously nonsense. --Tango (talk) 21:39, 26 July 2010 (UTC)[reply]
You are essentially asking about freezing water at constant density (i.e. by not allowing the water expand as it freezes). Assuming an sufficiently rigid container to counter the large pressures involved, I would expect to see a combination of normal ice and one of the high density ices such that the density of the mixture stayed constant. Dragons flight (talk) 18:28, 26 July 2010 (UTC)[reply]
Right. Note that below about 250K there is no stable liquid form at any pressure, so the result is bound to be ice of some type. Looie496 (talk) 18:34, 26 July 2010 (UTC)[reply]
Looking into this further, what would happen, I believe, is that the water would remain liquid as it cooled down to 250K, with the pressure rising steadily to over 200 million atmospheres. Then it would freeze into a mixture of ordinary ice and altered phases of ice. As it continued to cool, it would evolve through several combinations of phases, with the pressure slowly dropping but remaining in the hundreds of millions of atmospheres. As it approached absolute zero, you would end with a mixture of about two parts ice XI to one part ice IX -- assuming that the container was totally filled with water at the start and totally nondeformable. Looie496 (talk) 19:55, 26 July 2010 (UTC)[reply]
I think that is almost but not quite right - ice can form at -1C and the pressure increase. At 20% normal ice (at -1C) the pressure would be 200MPa and then other forms of ice could form.the figures in the last sentence may be quite far out Nevertheless there would definately be normal ice in the box below 0C below 200MPa (above 250K) 87.102.43.171 (talk) 20:07, 26 July 2010 (UTC)[reply]
The scholarly consensus (e. g., PMID20504748) is still that humans can't detect the Earth's magnetic field, the cited article notwithstanding. MRI involves fields stronger by many orders of magnitude, so a moderate sensitivity to them wouldn't mean all that much. Looie496 (talk) 18:17, 26 July 2010 (UTC)[reply]
A human would be able to magnetically detect a magnetar from a good long distance off, since at 1000km away, the magnetic field is lethal. It's not strictly relevant; I just mention this fact whenever I can. Paul (Stansifer)03:00, 27 July 2010 (UTC)[reply]
I think my group is using conductive indium tin oxide cover slips for electric field experiments. However, my group doesn't know what happens if you culture epithelial cells on it -- any predictions? Would poly-L-lysine coating -- used for helping cells adhere -- ruin the conductive properties, or no? John Riemann Soong (talk) 18:53, 26 July 2010 (UTC)[reply]
The issue I can see would be if polylysine (basic) reacted with the indium tin oxide - if the indium tin oxide film is very thin (ie 1 atom) you could end up stripping that film by complexation with the polyamine... However I imagine the film will be much thicker.
I have no idea about culturing cells on indium tin oxide - if indium or tin is toxic to your cells then that could be a problem - beyond that no idea. It's not clear why a conductive glass slide is needed - wouldn't anodised aluminium be just as good for culturing cells and doing field experiments?87.102.43.171 (talk) 21:28, 26 July 2010 (UTC)[reply]
Thank you so much. I feel a little dumb because we have some impatiens in our yard, but this looked a little different to us. I appreciate your time in answering. Alanraywiki (talk) 22:00, 26 July 2010 (UTC)[reply]
Help me identify these intercellular bridges, follow-up?
I've put up some of my images at User:John Riemann Soong/intercellular bridges. I'm trying to puzzle out what kind of intercellular bridges these are. These bridges are between A549 lung cancer cells. Help is appreciated!
for background, most of the white things that don't appear to change appearance with rotations are vesicles, not gold nanorods. Particles that go black-white-black or "wobble" are gold nanorods. I excluded most of the video of course as they are much too big, but I can upload huge (~30 MB) animated gifs if necessary. A brief description of what happened on each day is on the page I linked to.
I've been reading this paper to try to help me identify these bridges. Do any of them consist of membrane nanotubes at least internally? I don't think I have any "tunneling nanotubes" right? Am I observing type I epithelial bridges, or just mere filopodial bridges? John Riemann Soong (talk) 23:52, 26 July 2010 (UTC)[reply]
July 27
Can a gas shield the Earth?
Can we release a gas which will shield the Earth from sun rays and reduce global warming? (That would be the equivalent of CO2 but reflecting heat instead of absorbing.)--Mr.K.(talk)11:17, 27 July 2010 (UTC)[reply]
The sun emits most of its energy in the visible range of the spectrum. I don't know of too many gases that significantly reflect in the visible, are stable in the atmosphere, and are mostly harmless to the ecosystem. Also, of course, it would seem to be more rational to do less meddling with a large, complex, critical system, rather than more. --Stephan Schulz (talk) 11:34, 27 July 2010 (UTC)[reply]
(Actually, you have it wrong - the whole problem with CO2 is that it DOES "reflect heat" - thereby trapping the heat in our atmosphere instead of letting it radiate harmlessly out into space!)
The tricky part is that you need to find something that's able to reflect visible and UV light - but be transparent to infrared. That's because it would have to bounce away the frequencies of light where the sun is injecting energy into the planet - but not prevent the planet from radiating away waste heat as infrared light. The Greenhouse gasses like CO2 that are causing all of the problems are quite the opposite - they are transparent to visible light (letting sunlight into the planetary atmosphere) and reflect infrared (preventing waste heat from escaping).
So the material you're looking for wouldn't be a transparent substance like most gasses - because those aren't reflecting visible light - they are transmitting it. The material you're imagining would have to be bright white to look at - yet transparent to IR light. Clouds are somewhat like that - but they are tricky to manage. Water vapor is a greenhouse gas, like CO2 - but when the water droplets are just the right size and temperature to form clouds, they become opaque and reflect away sunlight. But it's tough to control water vapor - to have it form clouds and reflect light without becoming a greenhouse gas.
You'd also need something that was very cheap and non-damaging to manufacture (if, for example, it took a lot of energy to make - it might cause more problems than it solved). You need an ungodly amount of 'stuff' to fill all of that atmosphere densely enough. It would also have to not damage ozone, not be poisonous, etc. Ideally, you'd want something that would break down naturally - at just the right rate so that we could control it's effects - you wouldn't want something where some small misunderstanding of the Earth's environment caused us to use too much of the stuff and plunge the planet into a massive cooling spell. Overall, this kind of approach is very dangerous...it's hard to imagine that doing this would be sufficiently non-risky to be acceptable. The politics of doing this would be very tough to negotiate too...suppose one country decided to do this kind of risky planetary engineering without the agreement of all of the other countries on Earth?
The earth has natural cycles of heat and cold, and our industry only makes a small difference to the temperature of the earth. Yes, the risks and expenses of making such a system would make it completely impractical. --Chemicalinterest (talk) 12:02, 27 July 2010 (UTC)[reply]
In any case, if the earth is only 7000? years old it's questionable how we can know whether the earth has natural cycles or not and these natural cycles must be so short that we better be bloody scared. Nil Einne (talk) 21:31, 27 July 2010 (UTC)[reply]
No. There was a warmth period (global warming) in the time of the Vikings, which is why they moved to North America. They left when it started cooling, making it too cold for them to survive profitably. It was still cold throughout history until recently, when it started warming again. During that cold spell, the early immigrants to the US (the Pilgrims) had a hard time being established here because of the cold. --Chemicalinterest (talk) 13:18, 28 July 2010 (UTC)[reply]
See Medieval warm period and little ice age, both of which are fairly insignificant compared to the observed and projected warming of the 20th and 21st century, especially the MWP which was cooler than year 1900 depending on the proxy source. ~AH1(TCU)01:52, 2 August 2010 (UTC)[reply]
Clouds reflect a lot of visible light, but don't they also reflect IR? That's why it's generally warmer at night if there is cloud cover. --Tango (talk) 14:19, 27 July 2010 (UTC)[reply]
If you have an infrared thermometer you can actually measure this. If on a day with some clouds in the sky you point your thermometer in the direction of clear sky you get a very low reading (like -50 °C), if you point it toward a cloud you get a much higher reading (e.g. 0 °C). Count Iblis (talk) 15:38, 27 July 2010 (UTC)[reply]
Isn't that detecting the thermal radiation from the cloud, rather than reflected thermal radiation from the ground? --Tango (talk) 21:59, 27 July 2010 (UTC)[reply]
There is a big misconception circling around here - that gases "reflect" visible light or IR radiation. They do not - gases can scatter and absorb, but there is not mirror-like reflection unless there is a flat surface of some sort (which gases don't have). Gas molecules with polar bonds (e.g. C=O, C-H, O-H, C-F, etc.) tend to be good at absorption of long-wave IR radiation (The same gases also emit a lot when warm) which makes them greenhouse gases. An "anti-greenhouse" gas would need to be poor at absorbing long-wave IR (so it must not contain such polar bonds) and good at scattering or absorbing visible light. However, the common gases with nonpolar bonds such as N2 and O2 are transparent. Gases without polar bonds can be colored/non-transparent such as Cl2, but it is toxic, harmful and unstable so clearly we shouldn't be pumping it in massive quantities into our atmosphere. I am not aware of any gases which i) have no polar bonds, ii) are not transparent to visible or short-wave-IR, and iii) Could be released in massive quantities necessary to achieve a substantial cooling effect without disastrous side effects. However, if you remove the restriction to gases, sulfate aerosols might work (see Geoengineering.) 129.2.46.178 (talk) 01:02, 28 July 2010 (UTC)Nightvid[reply]
Some people think that there may be a way to protect the earth via a gas (See this article). Basically, a relatively small amountof SO2 in the stratosphere could 'reflect' some of the light that would have entered the atmosphere. Not sure if it really reflects (see above regarding gases absorbing or scattering light), but it is possible that it would exist as a fine particulate, maybe sulfates as mentioned above, that would reflect. As for cheap sources, there is quite literally tons of sulfur sitting in the Alberta tar sands that some people would love to find a use for...24.150.18.30 (talk) 02:50, 28 July 2010 (UTC)[reply]
A recent article in New Scientist argued that reduction of the UK's power generation and industrial emissions of Sulpher dioxide (by using 'cleaner' fuels) to lessen the acid rain impact on Scandinavia had, ironically, had little impact on the acid rain (because the main sources of Scandinavian SO2 were actually Continental), but had increased the UK's local warming by decreasing SO2 reflection of sunlight. 87.81.230.195 (talk) 10:16, 28 July 2010 (UTC)[reply]
There is not enough darkness in all the world to put out the light of even one small candle
Is this true?
Namely, if you had a small unobtrusive clear container of STP air in a remote and (perfectly?) dark region of space with a small wax candle burning inside, would black-body radiation drop the temperature low enough to extinguish the flame? -Craig Pemberton18:16, 27 July 2010 (UTC)[reply]
I assume you're thinking of something like the fact that water left outside on a clear night can freeze even if the air temperature is above freezing, because it loses heat to space, and air (not being very efficient at radiating heat) does not radiate enough heat back to the water to compensate. Whereas if the night is cloudy, it won't happen, because the clouds will radiate enough heat to keep the water liquid.
I am quite sure that effect cannot put out a candle flame. The limit of the effect is the heat that would otherwise be transferred by radiation from the air to the candle wick, if air followed the black-body law. But that's a pretty trivial amount of heat compared to what a candle generates. --Trovatore (talk) 18:23, 27 July 2010 (UTC)[reply]
Let's try some back-of-the-envelope calculations and see what they reveal. Let's assume that the container is a cube 10cm on each side, that the space is at absolute zero (actually, cosmic microwave background radiation makes it about 3K, but that's close enough to zero), that the container is a perfect black body and that the candle continues to have enough oxygen to burn by magic. The relevant law is the Stefan–Boltzmann law, which states that the power lost is , where A is surface area, T is temperature and . According to candle, a typical candle emits about 40W. We can now rearrange the Stefan-Boltzmann law and find the equilibrium temperature. . The candle will have no problem burning with the container at 56C (the air right next to the candle will be hotter). If we increase the size of the container, then the equilibrium temperature will be lower, for example a cube 1m on each side would have a temperature of -170C, which is probably too low for the candle to keep going (the air in the centre would be much hotter, but the outside would be very close to the point where oxygen condenses, which would cause problems). --Tango (talk) 18:47, 27 July 2010 (UTC)[reply]
As a minor aside, I will note that bringing liquid oxygen together with a combustible material in the presence of a spark or other ignition source is actually a very effective way of making a very impressive fire. While I have not tested this personally – and I would discourage any but the most qualified from making the attempt – I strongly suspect that dropping a lit candle into liquid oxygen would be very...exothermic...indeed. Making interesting reading (and viewing) are the numerous accounts of people lighting charcoal barbecues using a lit cigarette, a pile of charcoal, and a bucket of liquid oxygen — attached to a very long pole. TenOfAllTrades(talk) 22:03, 27 July 2010 (UTC)[reply]
(ec)A candle can burn as hot as 1930K - i.e. a temperature rise of 1637K, even if you froze the whole thing to absolute zero the candle would still release enough energy to burn (at least once you managed to ignite it). Ariel. (talk) 18:50, 27 July 2010 (UTC)[reply]
I quite like Tango's analysis above, but I fear that once the box gets large (and the corresponding mass and volume of air around the candle become significant) we will no longer be able to approximate the system as reaching a uniform air temperature. Instead, we will have a gradient of air temperatures ranging from 'quite hot' adjacent to the candle flame down to 'very cold' at the walls of the box. Assuming the box is under gravity then convection currents will also play a role. (If the box is not under gravitational or other acceleration, then we might have problems with the candle depleting the oxygen around itself and going out for that reason.) Conductive and convective heat transfer will become increasingly important in larger boxes. TenOfAllTrades(talk) 22:03, 27 July 2010 (UTC)[reply]
Indeed, my calculations are for the container, rather than the air. The air will have a temperature gradient, from the temperatures I gave at the edge to thousands of degrees at the candle itself. The exact details of that gradient are beyond my ability to calculate. --Tango (talk) 22:13, 27 July 2010 (UTC)[reply]
Per Fourier's law, the gradient will tend towards a linear isotropic temperature falloff after a long period of time. In other words, dT/dr = constant, where r is the vector from a test point to the candle heat source. In reality, two factors confound this calculation; there is not spherical symmetry (if the box is a "cube"), so depending on whether we have "imaginary nonconductive walls" or some walls with real thermal characteristics, that will break the linear isotropic assumption. We could call the walls "very conductive" and therefore at constant temperature at all locations along the wall, in which case they would serve as a boundary condition for the heat flux equation. Or, we could call them "very non-conductive" (much less conductive than air), in which case they would simply truncate an otherwise spherically symmetric solution. The realistic case, where the conductivity is "comparable" but non-equal to that of air, would be a complicated boundary value problem. The second problem is that air will convect and turbulence will exist; if the candle burns for an "indefinite period of time", we can assume a steady-state will be reached eventually, but it may be a very long time before that is the case. Tiny fluctuations in initial conditions of the momentum and angular momentum of each air particle will persist in a very unpredictable way. I agree with Tango, any realistic solution for the air temperature that does not rely on trivial-solution assumptions are extremely difficult. (Not surprisingly, these are the same calculations used to determine planetary energy-balance and surface-temperature equations in planetary science. The results can provide bounds on material composition, internal seismicity or radiogenic heat, and so on. There is good coverage in de Pater and Lissauer's Planetary Science text). The scenario described above is a lot like a miniature "hot gas planet" with an internal heat source. Nimur (talk) 02:34, 28 July 2010 (UTC)[reply]
Ah, yes, I forgot about the conductivity of the container. I made an implicit assumption that it was highly conductive, which I should have included in my list of assumptions at the beginning. Thanks! --Tango (talk) 13:05, 28 July 2010 (UTC)[reply]
Blood gives a typical volume of 5 liters, which is in sync with the 4.7–5.7 L range given in circulatory system. Of course none of this is specifically cited. Anyone with a medical text or similar ref handy? DMacks (talk) 19:41, 27 July 2010 (UTC)[reply]
"Ten" in this case does not refer to the question, but the username of the user whom the above user responded to, TenOfAllTrades. ~AH1(TCU)01:44, 2 August 2010 (UTC)[reply]
How much paneer cheese would I get per litre of milk?
Having read the paneer article I'm intrigued by the idea of making some myself, rather than buying salt-laden fetta cheese from the supermarket. What weight of paneer cheese would I get from a litre of milk please? Is it possible to make low-fat paneer cheese by using skimmed milk? Thanks 92.29.116.34 (talk) 23:19, 27 July 2010 (UTC)[reply]
It is not specific to paneer, but this website [7] describes turning 5 gallons (roughly 40 pounds) of milk into 6 pounds of cheese. So, using that ratio, 1 liter of milk should make about 150 grams of cheese. Dragons flight (talk) 23:42, 27 July 2010 (UTC)[reply]
Softer cheeses contain more whey, so they have greater yields. Cheddared cheeses are the opposite. Regardless, the total cheese and whey combined that is produced should be roughly invariant. Whey can be used in the place of water in a lot of cooking and is nutritious. -Craig Pemberton07:13, 28 July 2010 (UTC)[reply]
I've looked into and made paneer before. Skimmed milk usually isn't recommended because the paneer is said to be grainy and rubbery (haven't tried it myself) but I've seen it suggested half skim and half full works okay. I've used reconsituted (full cream) milk powder myself because it's cheaper and I don't think it will make that much of a difference to the taste or texture but I haven't actually tested it to see. I can't remember the yields but the above sounds roughly write, in any case if you use milkpowder the amount isn't going to be that different from the solids you put in, 1 kg of full cream milk powder yields 8 litre IIRC which means 125g for 1 litre which is about what Craig Pemberton found in the ref above. Nil Einne (talk) 09:43, 28 July 2010 (UTC)[reply]
Thanks. What about filtering it - where could I get some muslin from in the High Street? Or is something else suitable? The cost of full-fat milk means it would be more expensive than shop-bought cheese - is there anything I could add to it to stretch or bulk it? I do not want to use dried milk. 92.29.121.86 (talk) 12:29, 29 July 2010 (UTC)[reply]
July 28
Phlebotomy Laws
Where would I look things up about Canadian Phlebotomy Laws. What about patient consent ?. Can the Dr. make me take blood fr
om a patient, consenting? , or non-consenting? —Preceding unsigned comment added by Dean J Taylor (talk • contribs) 00:10, 28 July 2010 (UTC)[reply]
I don't know about Canadian law specifically, but I'm pretty sure it's the same as other similar legal systems in that sticking a needle in someone without their consent is an assault (or, maybe, a battery, depending on the terminology used in the jurisdiction in question). There are exceptions made for people trying to help someone who cannot consent (eg. they are unconscious, insane, a child, etc.). The exact details of those exceptions will depend on the jurisdiction and, as I say, I'm not familiar with Canadian law. --Tango (talk) 00:15, 28 July 2010 (UTC)[reply]
Of course taking blood from a a non-consenting person (in normal circumstances) is unlawful but I'm not sure the OP is asking about that. The question seems to imply that 'the doctor' is the employer and that the OP may be coerced into doing something he/she doesn't want to do. If taking blood is part of your job description then you may be obliged to carry out that duty. If this is a new task that the doctor is imposing on you then negotiation is in order. Do you have access to a local union? I am not an expert and this is not legal advice. Richard Avery (talk) 07:21, 28 July 2010 (UTC)[reply]
There would probably be a few other cases where medical treatment isn't really involved but consent isn't required to take blood, like a blood alcohol test compulsory under law (in many countries a police may be able to order a driver to undergo some test to determine their blood alcohol content) or a court ordered blood test for some other reason. Also someone who 'can't' consent may also include a suicidal person in quite a few countries where someone who is attempting/has attempted to commit suicide may be subject to suicide intervention and considered unable to refuse medical treatment. As per Richard Avery, if you are uncertain about what circumstances you may be required to take blood without the patient having given consent, you should consult a union or some other such authority who can hopefully advise you. Nil Einne (talk) 10:14, 28 July 2010 (UTC)[reply]
Your job description cannot oblige you to carry out an illegal act, though. If you think what the doctor is telling you to do is illegal, then you are legally obliged to disobey. --Tango (talk) 13:09, 28 July 2010 (UTC)[reply]
A question about Desmoplastic small round cell tumor question
[I have modified the heading from "A question" to "Desmoplastic small round cell tumor question" to facilitate subject-matter searches. I believe this is in order, but apologies if I am in error.] 87.81.230.195 (talk) 10:21, 28 July 2010 (UTC)[reply]
I’ve been thinking about a problem I see with current evolutionary theory (not that I’m a creationist). Sure, some genetic features for a given species in a given niche are better suited for survival and reproduction than other features. We constantly hear of examples of such features, like the giraffe’s neck. But in the case of the giraffe, and of all other species, each one has thousands of special adaptations, all of which presumably have been selected because of their efficiency. Now, my problem is that I can’t see how multiple features can be selected for at the same time, and yet I can’t see how they could be selected one at a time either. What if the member of some species has a beneficial trait and another member has a different beneficial trait? Now it would seem that if they are in competition, the traits themselves are in competition. But we never hear about this when the subject is being discussed. It’s always examples of beneficial traits discussed in isolation, as if the one being discussed is the only one at that time, in that species being propagated throughout their community. I’ve heard there is a name for this conundrum. Has it ever been discussed here? Eric155 (talk) 06:40, 28 July 2010 (UTC)[reply]
If you never hear of the traits evolving in competition and co-operation, then I can't think what advanced biology texts you're reading! Seriously though, that's pretty much the default way of thinking in modern evolutionary biology. The idea that traits evolve in isolation is responsible for people assuming irreducible complexity when they see things that must have evolved in tandem with other things. 86.164.66.83 (talk) 06:52, 28 July 2010 (UTC)[reply]
(ec) I'm not sure that there's necessarily a problem here. For simplicity's sake, let's assume that the original animal has traits a and b, each regulated by a single gene. It turns out that a mutation affecting a gives rise to dominant trait A, which confers a survival or reproductive advantage. An independent mutation in b gives rise to B, which also confers a survival advantage. The population now consists of a large number of individuals with the original genes ab, and a few with the beneficial new traits, Ab and aB. If A and B confer an advantage over a and b, the number of ab individuals will become depleted in the population as they are out-competed by the Ab and aB animals.
As you get more Ab and aB and fewer ab creatures, the likelihood is that there will be interbreeding between Ab and aB animals; some of whose offspring will now be AB. As the original ab animals disappear, the interesting competition becomes the one between the single-mutant Ab or aB animals, and the double-mutant AB animals. If AB in combination is more effective than (that is, confers a reproductive advantage over) the single mutants, it will gradually become more prevalent in the population. So I guess the short answer to your question is this — animals can acquire multiple beneficial traits because they interbreed, and because there is a pool of animals with a range of genotypes which survive each generation (it's not just one 'optimal' genotype which is cloned for all of the offspring of the next generation; there's significant mixing). TenOfAllTrades(talk) 07:04, 28 July 2010 (UTC)[reply]
I recommend Eric155 reads River Out of Eden by Richard Dawkins. This book is short in length and brilliantly suited to newcomers, like me, to the field of zoology and evolutionary biology. It is very readable and will answer Eric155's questions. Dolphin(t)07:54, 28 July 2010 (UTC)[reply]
I have long had a similar problem to the OP's, and had been thinking of posing a similar question here along the lines:
given that in any population scores if not thousands of phenotypical traits (mostly at biochemical levels not evident to the eye) are presumably all evolving simultaneously, how is it that the advantageous and disadvantageous ones, proportionally represented in each individual of the population, do not cancel each other out? (To crudely oversimplify, a squonkbird won't pass on its advantageously longer wings if its unconnectedly and disadvantageously weaker heart leads to its death before it breeds.)
Intellectually I agree they can't, because I fully accept that evolution is proven to proceed as extensively described, but intuitively it's hard to visualise. Can the total sub-set with each disadvantageous trait, and ditto for the advantageous ones, be validly considered as evolving separately, with the successful outcomes re-merging? I imagine that there might be some simple mathematical demonstration that the numbers really do work out, and if so I'd like to be able to point to it even if (as is likely) I can't myself understand it. (Hey, I'm willing to trust a mathematician! :-) ) 87.81.230.195 (talk) 10:45, 28 July 2010 (UTC)[reply]
Mutations tend not to be helpful. What would, for example, a wolf (or any other animal) with am extra-long neck have to give it an advantage. Its neck would be extremely hard to hold up unless it has more developed muscles and a strong heart to pump it up, along with extralong tissues of all kinds that are found in the neck. It also has to adapt to leaning down to drink water. All of these helpful mutations have to occur all at once, or the neck is utterly useless (i.e. the animal is a "freak animal"). If you take the mathematical probability of all of those helpful mutations occuring all at once, it is very low, definitely not able to occur in millions or even billions of years. (I am he in disguise). --98.221.179.18 (talk) 10:51, 28 July 2010 (UTC)[reply]
Most mutations are not things like "extra long neck." They are small changes to physiology. They do not have to happen "all at once." If you're actually interested in learning about what evolutionary theory says — and not just the bad parody of it that is given by the ID people — there are plenty of better explanations out there that you seem to have either missed or not understood. I am also not sure you can conceptualize how long a span of time 1 million years is, much less a billion years. --Mr.98 (talk) 12:15, 28 July 2010 (UTC)[reply]
The mistake being made in these questions is one of the most common misunderstandings about evolution - you can't approach evolution from a atomistic, particularistic viewpoint. evolution works by small advantages and small changes to entire organisms, not big advantages and big changes to parts of organisms. Let's take giraffes for an example. There was (by the theory) some paleontological period extending over millions of years in which having a longer neck was an advantage-niche that a species could occupy. the actual advantage is unknown, and probably constituted several advantages - e.g. a longer neck allowed for better detection of predators, better access to certain kinds of food, a more threatening, dominant posture (for purposes of breeding and defense). whatever that primal species was it had a normal but small distribution of neck sizes (just the way humans have have a normal but small distribution of heights), and the animals with longer necks where slightly more likely to survive to pass on their genes - they could see predators sooner, had better nutrition and thus better health, were less likely to be attacked and more likely to gain access to mates. Further, those of that species which did not have the internal biological structures needed to support a longer neck (stronger circulatory systems, exaggerated musculatures, etc) could not utilize the environmental advantages of having a longer neck, and would not gain any of the advantages. The entire system (longer neck and internal support structures) was required to take advantage of the niche.
you need to remember that this has nothing to do with the particular feature. sure, giraffes have long necks, but giraffes did not evolve long necks because it was advantageous to do so; giraffes evolved in a way that was advantageous in the environment, and that just happened to involve long necks. in a slightly different environmental context they might have evolved with very long legs and short necks. There's a strong tendency because of the way we think for us to use teleological reasoning - asserting that the effect we see in the world must have a specific cause that brought it about - when in fact this is less a specific effect than a by-product of other forces. --Ludwigs211:55, 28 July 2010 (UTC)[reply]
wwwwait! TenOfAllTrades you said about the mutations of genes. mutations ,which are very rare, are 99.9% of the time failures and make the animal, insect,etc. worse. Some are even deadly. And that statement is proven by experimenting; an example of mutation is two-headed snakes and albino squirrels which, as you obviously see, isn't better than the original creature. so, sorry, mutation doesn't make things better.--Horseluv10 12:05, 28 July 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)
"99.9%" is just a made up, fake statistic, along with your false "experimenting" snake example. It's true that there are a lot of non-beneficial mutations, but that's not the problem. Mutation rates just provide a background rate of variability for which natural selection can then act upon. Most mutations are small physiological changes that can add up over time. There is a lot of real scientific work on this, with precise understandings of gene flow and mutation rates and the mechanism of mutation and so on — not just hand-waving bad Creationism. If you want to have a conversation about how this really works and what the scientific arguments really are, that's fine, but this is not a general discussion forum where ignorant trolling (from any side) is really tolerated. --Mr.98 (talk) 12:15, 28 July 2010 (UTC)[reply]
Horseluv10 appears to be using the notion that mutations must be either good or bad - no random mixture is contemplated. Horseluv10 has cited examples like two-headed snakes and concluded Voila, mutations are bad - all of them! That is nonsense. Mutations are entirely random. We must expect that many of them, perhaps most of them, will be bad but all it takes is for one or two of them to be beneficial and those one or two will be retained in the gene pool whereas the disadvantageous ones will eventually disappear. Dolphin(t)12:32, 28 July 2010 (UTC)[reply]
Advantageous mutations are really harmful to the creature and result in a lower rate of selection. You can see how many advantageous mutations have occurred in man's history or any animal's history. Mutations generally are corrected or result in cancer or do not affect the creature at all. Mutation is disorder, and it cannot produce order except for the occasional good mutation which is buried under countless bad mutations. If all of those mutations happened to a creature and it impossibly remained alive, then that creature would be unrecognizable. Dolphin51, your statement seems to me to be bordering on ID. How can the good changes be saved and the bad changes be deleted if nature, with its bad mutation-causing sunlight and bad mutation-causing chemicals and other bad stimuli, generally leans to the bad and decaying side? Animals die; they do not become more healthy as they get old, which shows that helpful mutations are practically nonexistent. If you have one real dollar bill buried in a huge pile of counterfeit ones (or whatever your currency is), that whole pile is practically useless monetarily, even though it does contain a dollar bill. But suppose Nature (represented by a windstorm) came and blew away all counterfeit dollar bills, leaving just the real one. That would be evolution in action. If such a thing could be observed, it would prove natural selection is capable of discarding bad mutations and keeping good ones. --Chemicalinterest (talk) 12:57, 28 July 2010 (UTC)[reply]
Dear Chemicalinterest. Please provide some references for your bullshit. And while you're at it, although it'd be hard to make it factually correct, at least try to make your argument logically and linguistically followable. Aaadddaaammm (talk) 13:47, 28 July 2010 (UTC)[reply]
(EC with above) Your analogy is silly but let's go with it. Let's say I'm so evil dictator and I have millions of slaves. I want that real dollar bill, perhaps it has sentimental value. I send my slaves to each get a bill from the pile. If they come back with a counterfeit I shoot them in the head. (If they come back with nothing I also shoot them in the head). Guess which of my slaves will be alive at the end? The one who found the dollar bill. Let's use a less extreme analogy. This time I'm not quite so evil. I don't kill my slaves. I do require each one of them to pick up a dollar bill. For the one who finds it, I let them spend that dollar bill however and whenever they want. One of my slaves is going to find that dollar bill and they now have some small advantage over their fellow slaves since they have this dollar bill to spend when they want. Nil Einne (talk) 14:03, 28 July 2010 (UTC)[reply]
(more ec) To keep with the analogy: This happens all the time. There is a mountain of rocks mixed with gold, and yet we select the gold out from the mountain. There is a mountain chain of rocks on the rock, and we still manage to pick out the Carrara marble. And while there are plenty of mutations, of course only those in the germ line affect evolution - if I remember correctly, there are on average about 4.6 mutations in the genome of each human. Many of those are neutral, some are advantageous in certain situations, and some are disadvantageous. Of course, the bad ones are selected out fairly quickly, leaving the "good" ones. --Stephan Schulz (talk) 14:09, 28 July 2010 (UTC)[reply]
I would hesitate to use those analogies, simply because they invoke an intelligent agent (a human being) to apply the fitness criteria. In truth, the problem is that the original 'pile of money' analogy is a crappy analogy that is divorced too far from reality to be the basis for drawing meaningful conclusions. An analogy that would be better – though still not good – would be one that involved dollar bills that could reproduce. (Ultimately, reproductive success is the basis for natural selection.) Suppose we take a million one-dollar bills, and impose a different mutation on each. All but one of the mutations is deleterious, preventing those bills from reproducing and passing on their defective (or 'counterfeit') gene. For simplicity's sake, we assume that the gestation time of a healthy dollar bill is one day, and that each healthy bill is able to produce one offspring per gestational period. Today I'll have 999 999 unsuccessful bills, and 1 viable one. Tomorrow, I'll still have the same 999 999 counterfeits, but I'll have 2 live ones.
That sounds pretty unsatisfying — the pile is still mostly junk. Something remarkable happens by the time I get out to about three weeks, however, when I'll have roughly equal numbers of unsuccessful bills and viable ones. By the end of a month, I'll have about a billion live dollar bills; only one in one thousand notes in the pile will be counterfeit. That's the power of natural selection over multiple generations. Note that this process still works even if it isn't a stark alive-dead or fertile-barren choice. Even small advantages add up over sufficient generations. Let's say that a particular mutation confers a very small advantage: on average, a 1% greater number of offspring in each generation. After ten generations, the population with the mutation will have expanded by about 10% more than the population without. After a hundred generations, that 1% advantage turns into 2.7 times as many offspring. After a thousand generations, that tiny little 1% advantage will be parlayed into twenty-one thousand times as many offspring — the original, slightly less advantageous version of the gene will be nearly invisible in the population. TenOfAllTrades(talk) 14:33, 28 July 2010 (UTC)[reply]
That analogy relies on the theory that good mutations are naturally selected, while bad ones are thrown away. It is not the case. Very rarely do cancers disappear (harmful mutations) or "good" mutations such as photographic memory get selected until everyone has photographic memory. --Chemicalinterest (talk) 15:04, 28 July 2010 (UTC)[reply]
Actually, successful mutations are selected in cancer. With loss of checkpoints in replication and increasing genomic instability, the rate of mutation tends to increase within a malignant tumor. Mutations which confer resistance to apoptosis, resistance to immune system attack, tolerance for hypoxia, more rapid cell division, and (after treatment begins) resistance to chemotherapeutic agents are all selected for (and observed in real tumors). As in populations of animals, the tumor cells that develop survival-impairing mutations do die off (or become a smaller fraction of the tumor mass) — but the death of individual cells doesn't eradicate the entire tumor. In real life, late-stage tumors tend to grow faster than early-stage ones; they've accumulated more 'beneficial' mutations. Natural selection isn't some supernatural ethical judgement; there isn't a magical preference for anything that humans would deem 'good'.
Look, it would probably be helpful if you just gave us a link to whatever creationist (or crypto-creationist 'intelligent design') website you're getting your material from so that we can hook you up with one of the many competent, clearly-written rebuttals of these terrible analogies. Better yet, read intelligent design and evolution, and let us know which concepts you're still confused by. TenOfAllTrades(talk) 15:23, 28 July 2010 (UTC)[reply]
All of this, while emotional, does not actually advance your argument one bit. Having a spontaneously mutating tumor in your organism is not the same as being a mutant yourself.--91.148.159.4 (talk) 16:38, 28 July 2010 (UTC)[reply]
What is the evolutionary cost of a photographic memory? Does it get you laid more? Do people with photographic memory have more children? When they mate, their children probably won't have a photographic memory. Such is the highly chaotic nature of personality. Also, it doesn't suit most species to be immortal. It's actually a bad thing for the species -- you get tons of people with "old genes" and adaptation slows down. People usually get cancer after they have children. Evolution is a little cruel sometimes -- it doesn't care what happens to the parents so much after they reproduce. John Riemann Soong (talk) 15:29, 28 July 2010 (UTC)[reply]
There wouldn't be so much variety. If one type of animal was most suited to its area for reproduction, it would dominate and all other animals that are less adapted would be blown away by natural selection. The multitude of types shows that God create the world and enjoyed having large varieties of animals. The lack of missing links (and their very name) shows that animals do not change. --Chemicalinterest (talk) 15:47, 28 July 2010 (UTC)[reply]
Ever heard of ecological niches? I'm sure your god enjoyed making parasitic intestinal worms, and the sound of excellently designed carnivore teeth piercing the necks of small lambs fills him with inexpressible joy. I'm glad I don't know him, though knowing his friends is bad enough.--91.148.159.4 (talk) 16:38, 28 July 2010 (UTC)[reply]
There is no solid evidence for "photographic memory" in the usual sense to begin with. In humans, memory is very much trainable, indicating that genetic variation is at best one factor. And humans have indeed evolved to have outstanding memory over time. --Stephan Schulz (talk) 15:34, 28 July 2010 (UTC)[reply]
nearly insurmountable barriers
Don't forget group selection and sexual selection guys. They massively accelerate evolution and it really becomes less of a "mutation because of chance" and more of "reassortment and recombination of traits".
In fact, there are "insurmountable" barriers that evolution doesn't like to cross. Take for example, the electron transport pathway. In high school they tell you it gives you 32-34 ATP or whatever per glucose molecule, but IIRC a lot of energy is still wasted in that transition from cytochrome c oxidase to oxygen -- that final jump is huuuuge compared to all the previous jumps, and ATP synthase utilises only a fraction of that final redox reaction. The rest is wasted as heat. It would really give all eukaryotes (and all aerobic bacteria) more useable energy to develop a "cytochrome V complex" in between....but you see, the electron transport chain is such a fundamental pillar of cell life that nature usually punishes any mutant cells that mess around with it. (Not to mention, it is probably hidden away in a protected area in most genomes, to prevent damage to these critical genes).
The same goes for why plants don't simply avoid photorespiration by modifying RuBisCO by only allowing carboxylation and not oxygenation (both are Lewis acid'ish reactions) -- they work around the inefficiency of this enzyme by using C4 carbon fixation or Crassulacean acid metabolism on top of RuBisCO. Once complex multicellular organisms get ... complex, they usually refrain from tinkering with their fundamental machinery. The changes would just be too big.
Since Chemicalinterest seems to be uninterested in reading the relevant articles on the topic (evolution, intelligent design, or even missing link, which he seems unaware is a misnomer), preferring instead to argue pointlessly, I don't intend to continue responding in this thread. I encourage other editors (who are interested in keeping this a Science Reference Desk) to do the same. TenOfAllTrades(talk) 16:52, 28 July 2010 (UTC)[reply]
The proof that giraffe needed more than one genetic change in order to look the way they do is that their necks are long because their legs are long. A short-necked giraffe would be unable to reach the ground in order to drink - so the long neck and the long legs had to evolve together. If the giraffe had first evolved a long neck - then the long legs would be unnecessary - so they must have started getting longer legs and needed to evolve longer necks in order to reach the ground! There is much more than that going on though - their hearts are stupendously powerful in order to pump blood all the way up those long necks. Read Giraffe#Circulatory_system to see the huge range of problems that long neck causes for the animal. It's heart is two feet long - it's blood pressure is twice that of other mammals - it has special valves in the arteries around the brain so that when it leans down to drink, the extra pressure doesn't cause it to black out! The legs have a specially built blood supply to prevent the huge pressures from exploding the veins and arteries. There is a lot more to the Giraffe than a longer neck!
So evolution had to change multiple aspects of the giraffe more or less at once. Because of the implausibility of genetic change for long legs, long neck, big heart, neck valves, etc all happening at once in one individual, the changes had to have been gradual. A few centimeters of extra leg length making it easier to reach higher branches, a few centimeters of neck length allow the animals to drink from shallower pools, a little extra heart capacity allowing for longer life and increased breeding success as pumping the blood higher put more of a strain on the organ. Round and round that cycle for 20 million years - and you go from a fairly normal-looking, deer-like Climacoceras to a modern giraffe - one centimeter at a time.
I used to live for a while in Kenya as a child - and on frequent occasions we'd go to the Nairobi game reserve and watch giraffes. It's really noticeable that the umbrella-shaped trees in the park were precisely high enough that the local giraffes could JUST reach them by stretching as far as their legs, neck, snout and tongue could reach. As tall as those animals are - they looked like they were standing on tippy-toes to reach the leaves! A giraffe with just a few inches of extra reach would have no trouble finding food...one that's just a few inches shorter would have a much harder time of things. It's not just the legs and neck - the snout and even the tongue is long. Conversely, trees that are shorter lose most of their leaves - they need more water and nutrients to produce leaves that do them no good because the giraffe get them - leaving them less food and energy for reproduction. A tree that grows just a few inches taller than the tallest animal can avoid the worst of the ravages of the Giraffe. Clearly the trees and the giraffe are locked in an evolutionary arms race.
Steve: without disagreeing (because I think what you said is reasonably accurate), be careful of the 'had to' language. saying 'had to' implies all sorts of misleading things (that 'evolution' is a particular thing, that giraffes are somehow a necessary result, even that the modern giraffe is somehow implicitly present in all of its evolutionary ancestors). A few million years ago there were creatures which were distinctly not giraffes; environmental pressures turned them into modern giraffes over time, but environmental pressures could have turned them into a wide assortment of creatures. there is no particular 'thing' called 'evolution' that 'does things' to change creatures; 'evolution' is just a code-word to point to the numerous processes by which species consistently change in response to a consistently changing world. --Ludwigs212:38, 29 July 2010 (UTC)[reply]
OP eric155 back. Thanks all for an invigorating discussion. I still feel at sea on this question though I will read more. I'm thinking of the various references to giraffes above. I've long thought that the traditional evolutionary example of the giraffe is hackneyed and a red herring. Everyone sees the long neck, to the exclusion of all else. As Steve and others pointed out, that long neck needs a strong back to support it, and that back needs special legs to support it, and they all need a specially powerful heart to keep them fuelled and so on. It means that the neck has ancillary phenome traits which from the head right down to the toes, probably hundreds of them. I guess my question was how does nature select when so many traits need to work together to effect a functional organism. So, what's the point of a longer neck if the giraffe strains its back from the effort.
One of the most distinctive and apparently retrograde features of evolutionary adaptation, is that any beneficial mutation must have IMMEDIATE beneficial effect, otherwise it is just a bad or neutral mutation, and will not be selected for. That caveat is to many people the most puzzling aspect of the process, especially because human life is so much a planned affair where we forgo immediate benefits in order to achieve advantageous long-term goals. How nature can work without recourse to any teleological vision and yet end up with organisms of infinite and wondrous complexity is often baffling. It would mean that potential traits of immense power are obliviously ignored just because they do not have an immediate effect.
Part of the answer seems to be that the environment selects via the structure of the whole organism, not via single genes. I believe that Dawkins makes this point somewhere. But to me it raises the further question then of how a complex trait, one which includes many sub-traits, such as the giraffe's neck combined with its back, legs, heart etc can be propagated via the genome, which would have to select for multiple traits all across the genome. And of course the kernel of my question is this, briefly: If beneficial mutations are rare, then how much rarer would it be for an organism to have, by sheer happenstance, a multiple of these mutations? Allied to this problem is another one I also have, and that is simply how a beneficial mutation, a mere blip in the organism's history manages to survive. Don't forget that most individuals of a species die before they can reproduce. In many species only 1 or 2 percent make it. Now, the forces leading to extinction are so massive, I keep thinking that they would make some small new "beneficial" mutation nothing more than a tiny noise, inundated by far more powerful forces. It's like saying that having the beneficial mutation of eyebrows will make a difference when your village is attacked by marauders or a volcano explodes. How many millions of beneficial mutations disappear in the face of these vast destructive forces? Eric155 (talk) 07:59, 30 July 2010 (UTC)[reply]
That is actually an important point that often gets overlooked in simplified explanations: many potentially beneficial mutations will not survive following exactly that sort of situation, and neutral mutations will propagate simply because the organisms with them happened to survive and reproduce better. This effect is more pronounced in small populations, where genetic drift is more significant as a result. In large populations, it averages out a bit more, since a potentially beneficial mutation, or a beneficial combination of traits, will be more likely to arise several times, making it more likely that some individuals with it will survive long enough to reproduce. 86.164.66.83 (talk) 14:36, 30 July 2010 (UTC)[reply]
Do blackholes tear holes in space-time?
According to General Relativity mass create "dents" in space-time. But can a gravity well be so strong that it rips the fabric of space-time? 148.168.127.10 (talk) 13:52, 28 July 2010 (UTC)[reply]
You can interpret the singularity and the centre of a black hole to be a hole in space-time, I suppose. In reality, we don't know what happens there. The maths goes crazy, which is a very clear sign that we've made a mistake somewhere in our theory. --Tango (talk) 14:36, 28 July 2010 (UTC)[reply]
It is worth noting that singularities (at least as predicted in general relativity) have literally zero size. Qualitatively, I don't think I would generally refer to a zero-size object as a "hole", since that generally tends to suggest a space large enough to fit something through. Dragons flight (talk) 15:55, 28 July 2010 (UTC)[reply]
What makes more sense is that "black holes" force out all empty space from the event horizon in. That empty space as we now know has an energy and volume that cannot be ignored. this is how gravity works: it is the vacuum energy created by the condensation of extra empty space around the surface of matter trying to displace the matter or get "back in" to where it once was. Something that virtually all physics laws have taken for granted is that empty space is uniform throughout spacetimud. that is why we can't figure out black holes, we are using archaic laws of physics that have the empty space or as I like to call it aether "built in" to the equasions. Basically, we will never be able to understand "black holes" if we keep forcing the current laws of physics down the throats of black holes. it is similar to trying to both locate and measure an electron. the tools we use to do those things inherently prevent us from achieving the goals. —Preceding unsigned comment added by 165.212.189.187 (talk) 13:47, 29 July 2010 (UTC)[reply]
how many people have drifted off to space irrevocably while on moonwalks
how many people have died a cold and lonely death after drifting off to space from one of their moonwalks and not being able to get back to their ship? 92.229.14.166 (talk) 13:56, 28 July 2010 (UTC)[reply]
You seriously never heard of the Challenger disaster then? These things are big news. I don't follow space news myself much but these things are big enough news that most people do hear them, whoever they are. This one would be even more so since it would have been the first time it happened (that we know of), and 'lost in space' or 'earth's latest satellite' also makes a great headline (even if in reality the body probably would burn up in the atmosphere before long so would join everyone else on earth). Nil Einne (talk) 07:33, 29 July 2010 (UTC)[reply]
No-one has died during a moonwalk or spacewalk (although Leonov got dangerously stuck during his Voskhod 2 walk). Almost all spaceflight casualties have all arisen during either launch or reentry (the scary energetic bits of flight); only Soyuz 11 happened on orbit. It is impossible to float away from the moon - lunar escape velocity is 2.4km/s, vastly more than the speed a person could attain by jumping. - Finlay McWalter • Talk14:06, 28 July 2010 (UTC)[reply]
Even the Soyuz 11 disaster happened during re-entry, it was just early on in re-entry so it was still "in space". It wasn't in orbit, though: it was after they fired the retrorockets. --Tango (talk) 14:44, 28 July 2010 (UTC)[reply]
I assume you mean "space walk" not "moon walk"? If not, you should know that there's gravity on the moon. You weigh less on the moon (about 1/6), but you certainly don't weigh zero. You couldn't "drift away" from the moon any more than your could on Earth.
You'd be hard pressed to drift away on a space walk, too. Usually they're tethered. They used to occasionally use thruster backpacks instead, but they don't do that anymore for whatever reason.
If you did somehow unhook your tether and drift away you'd probably still be OK. They never leave the ship (or station) completely unattended. If you drifted away from the space shuttle they could track you on radar and follow you. I'm not sure what the procedure is for dealing with an astronaut that somehow drifted away from the space station, but I suspect that they could jump in their Soyuz capsule and go pick you up that way. I'm not sure how fast they can suit up and get that thing ready for launch, though. APL (talk) 16:06, 28 July 2010 (UTC)[reply]
APL is referring to the manned maneuvering unit ("rocket backpack"). The "whatever" reason they no longer use it was a massive overhaul and reassessment of all hazards, risks, and safety considerations, following the Challenger disaster (as described in our MMU article). Though not in any way related to the Challenger incident, the MMU was one of a number of "risky" things that were eliminated from the American manned space program as part of a massive risk reduction campaign. Nimur (talk) 05:05, 30 July 2010 (UTC)[reply]
Oh, Just remembered, you may be interested in the legends of the Lost Cosmonauts. The story goes that some number of cosmonauts were lost, but Russia went to great lengths to erase them from history. Almost certainly nonsense, but just plausible enough that it makes a great campfire story. APL (talk) 16:10, 28 July 2010 (UTC)[reply]
You wouldn't drift away very fast (unless you pushed off quite hard, which you just wouldn't do), so they would have until your suit runs out of air/power (whichever comes first, I'm not sure which it is) to come and get you. The Soyuz has an airlock, so the pilot doesn't need to suit up, the drifting astronaut can enter the airlock without decompressing the rest of the Soyuz. Also, spacewalks on the ISS are always done in pairs, so the partner would already be suited up. Whether they could easily get to the Soyuz, I don't know (it would depend on which station airlock they were using, I guess). --Tango (talk) 16:18, 28 July 2010 (UTC)[reply]
Ok, so I have noticed on weather.com there is an hourly forecast that includes precipitation percent. For the past couple of days, as an example, I have seen it say over an 8 hour period, 10am - 20%, 11am - 20%, 12pm - 20%, 1pm - 30%, 2pm - 30%, 3pm - 30%, 4pm - 30%, 5pm - 30%. Now statistically, that would say to me that there is only a 8.6% chance ((0.8^3)*(0.7^5)) that it will not rain at some point during that 8 hour span, but my experience shows that it does not frequently rain during that 8 hour time. So is there a special meteorological method that one is supposed to use to interpret these precipitation chance %s? Googlemeister (talk) 15:20, 28 July 2010 (UTC)[reply]
I have wondered about those percentages as well. You often see the daily chance at around the same figure as the hourly chances, which doesn't seem to make sense. --Tango (talk) 15:55, 28 July 2010 (UTC)[reply]
Your calculation is assuming that the hourly chance of precipitation can be interpreted as uncorrelated, independent events. In reality, the chance it rains at 1 PM is highly correlated with the chance it rains at 3 PM, etc. Consider the following example. I tell you that I will give you a dollar at a random time tomorrow. Then the probability you get a dollar between 1 PM and 2 PM is 1/24. Treating those hourly probabilities as independent you might then conclude you have a 1 - (23/24)^24 = 64% chance of getting a dollar tomorrow, but that is false since I have guaranteed you a 100% chance. In the limit of totally dependent events, one might predict the probability that it rains tomorrow is equal to the max of the hourly probabilities (i.e. 30% in your example). Much of the time weather forecasts seem roughly consistent with an assumption like this in that they predict a daily chance of rain not much different from the max of the hourly chance. In general, we would usually expect that the true probability of rain tomorrow is intermediate between the max value and the value calculated via your method, but it is not possible to predict an actual value without additional knowledge of how the hourly predictions relate to each other. Dragons flight (talk) 16:21, 28 July 2010 (UTC)[reply]
The forecast probabilities on weather.com are bogus -- they've annoyed me for years. You can safely assume that a higher "probability" means a greater likelihood of rain, but the actual numbers are pretty much meaningless as far as I can see. The only probabilities you can rely on in my experience are 0% and 100%. Looie496 (talk) 20:40, 28 July 2010 (UTC)[reply]
To those posting here who are, I'm guessing, mostly Americans - be aware that many weather services around the world do not provide percentage chance of rain forecasts. The one I know well is Australia's Bureau of Meteorology. One argument against that I have heard from some of its staff is that a percentage chance of rain forecasts is a cop out. It cannot be wrong. If it rains, they can say "We said it might" and if it doesn't, they can say "We said it was a low probability". HiLo48 (talk) 22:27, 28 July 2010 (UTC)[reply]
safety procedures
Are these situations worrisome enough to warrant attention?
Perchloric acid and nitric acid being stored next to organic solvents
Bottles of acids like TFA, HF and sulfuric acid being stored in rusty metal containers-- is the rust a sign of a leak problem? (Don't worry the HF is stored in polyurethane).
A nurse storing a bottle of NaF next to the clinical trial medications in a research unit?
This is bad laboratory practice. Of course, everything will be fine until you have a major fire in the lab, in which case the laziness will make the fire much worse and much more dangerous to try to extinguish. In most labs, it is really easy to design a storage system which keeps strong oxidizing agents away from flammable organic solvents, and putting such a system in place is a good reminder that you should try to envisage the worst case scenarios when thinking about safety measures.
This is fairly normal laboratory practice (in virtually every lab I've worked in). The rust is not necessarily a sign of a leak problem from the bottle inside, the atmosphere in chemical storerooms is often propicious for corrosion (because of drips on the outside of bottles that evaporate, or humidity levels, or condensation). The metal container provides a small amount of shock protection, and also a small amount of containment if the bottle breaks, but that's not the main reason. Simply, the label on the metal container is often easier to read than the label on the bottle!
I wouldn't do it, because it seems like a needless risk; on the other hand, you have to ask yourself where else the nurse would have to store it. In a lab, you can usually find an appropriate place to store something, but "storage resources" can be more limited in a clinical context. If you know that it's NaF, then at least the labeling is adequate!
Also, is it normal for bottles of sulfuric acid, etc. to become really sticky? I didn't notice this before -- it was the first time I was rummaging without gloves (was looking for H2O2). John Riemann Soong (talk) 16:17, 28 July 2010 (UTC)[reply]
In my opinion, this question is asking for the kind of personal professional advice that we aren't really capable of giving. We can't really tell you what is safe or reasonable without knowing both the details of what you are doing and the legal / professional standards that apply to your particular workspace. You would probably be much better off discussing the issues with your colleagues and/or a local safety officer. Dragons flight (talk) 16:28, 28 July 2010 (UTC)[reply]
We can't give professional advice, but we can (and often do) reply to general queries like this. JRS is only an undergraduate (as he has made clear in his many previous posts), so has no power to change anything! Physchim62(talk)16:33, 28 July 2010 (UTC)[reply]
When someone asks for specific safety advice about their work environment I see that as less a general query and more analogous to looking for personal medical advice. If our advice is good, then there is no harm, but bad safety has the potential to cause personal harm in a way that is very analogous to bad medical advice. In addition, since none of us can see his personal work area, it is very possible that us strangers on the internet might be unaware of factors that change the situation significantly. For example, rusty metal containers might be innocuous 98% of the time, but 2% of the time an inspection might notice that the rust is caused by vapors from an improperly stored strongly oxidizing chemical (e.g. NaClO). Also, there are situations where subpar practices might be tolerated (even routine) in one lab environment while the same practices would be illegal and/or grounds for firing in another lab. We don't and can't have a complete picture, and hence I still think it is much better for JRS to discuss safety concerns with a more senior colleague than to rely on the advice of people on the internet. Dragons flight (talk) 17:54, 28 July 2010 (UTC)[reply]
Jugs of strong acids (2.5 L concentrated sulfuric, etc.) often are coated with a thin layer of rubber/plastic, and that is what seems to become sticky. I assumed it was either swelling or decomposing a bit in the lab atmosphere (organic vapors in an orgo lab and/or acid vapors in an acid storage cabinet), plus picking up misc dirt in the stickiness. The test would be to remove part of this coating on a new bottle and see what happens over time. DMacks (talk) 16:52, 28 July 2010 (UTC)[reply]
In my experience, the problem is particularly bad with sulfuric acid bottles; with nitric acid, you tend to get the plastic coating hardening rather than softening, especially around the top. I guess its just that university research labs keep these bottles around far longer than the chemical suppliers would like ;) Physchim62(talk)16:59, 28 July 2010 (UTC)[reply]
If you have the slightest concerns or questions about safety, I encourage you to ask the person who organizes the lab storage about them. Ordinarily such people are delighted to see that people in the lab are thinking about safety -- usually their problems go in the other direction. Looie496 (talk) 20:33, 28 July 2010 (UTC)[reply]
Seconded. It is never foolish to seek to improve your knowledge of factors affecting Health & Safety. Any professional workplace (including academic or research establishments) should have a Health & Safety Department or at minimum a properly qualified person to consult, and clear procedures should be in place, training be given, and advice be available on request: if the ethos is one where concern for safety is thought foolish, I for one wouldn't care to work there at all (and yes, I have worked on sites involving laboratory, and mechanical & electrical engineering, facilities). You, JRS, are clearly well educated and intelligent, so if you're unsure about something's safety you either haven't been properly/fully instructed regarding your workplace's H&S by those who should have done so, or there is genuine cause for investigation and reassurance - or correction. 87.81.230.195 (talk) 23:27, 28 July 2010 (UTC)[reply]
It's not just my lab. Fellow interns in other labs describe a lot of the same things - clogged/disorganised fume hoods where the hoods are treated as storage areas. I mean, in training we were told to look out for these things, but I'm not sure in practice if it matters? If it does, it's the sort of thing I'd want to fix quietly since I've had a lot of favours done for me and I don't want to cause too much trouble.
Btw, can lab vapors cause that much rust? The containers are thoroughly corroded. Should HF be stored out in the open? With its translucent plastic container I almost thought it was just another bottle of alcohol -- I freaked out for a bit after I touched it and realised what it was, lol. John Riemann Soong (talk) 00:06, 29 July 2010 (UTC)[reply]
A volatile strong oxidizer (of which NaClO is perhaps the most common example) can thoroughly rust all available iron pieces after less than 24 hours if you leave a bottle open in an enclosed space. So it is certainly possible, and will depend on what is available. When not immediately in use volatile corrosive compounds should always be kept in closed containers. After all, if the vapor can eat iron it is generally likely to be bad for other lab equipment as well as the skin of young researchers. Dragons flight (talk) 03:07, 29 July 2010 (UTC)[reply]
JRS, only you can be fully aware of your own circumstances and constraints, but if I were in your position and seeing the things you are describing, and finding they were representative and not isolated, I would be investigating opportunities to transfer to a better-run establishment, and should I succeed in transferring I would consider passing my observations, perhaps anonymously, to whatever government authority has legal jurisdiction over Health & Safety in the locality concerned, in order to prompt an official inspection. In the UK that authority would be the Health & Safety Executive. Some might feel that it would be better to make representations to a senior level in the establishment or its parent organisation, if any, but in my experience standards are set from top management on down, and if things are that bad, the top isn't caring.
You say " . . . I'm not sure in practice if it matters?" H&S rules are never dreamed up for the sake of inconveniencing everyone for no good reason (though they can be inappropriately applied). Where H&S rules are flouted, it may not appear to matter for long periods of time without incident, right up to the moment when someone is maimed or killed. 87.81.230.195 (talk) 17:42, 29 July 2010 (UTC)[reply]
woodpecker question
This is an uncited and questionable excerpt from the Red-headed woodpecker article.
"Like all woodpeckers, this species's tongue is actually one-half to two-thirds longer than the length which the bird uses for feeding. The extra length is wrapped longitudinally around the brain, between the brain and the skull, to provide added padding for the bird's head's repeated decelerations against wood. The tongue thus helps in preventing the brain from bouncing against the skull, which would cause brain damage."
This sounds extremely suspect to me, but I am far from expert in the anatomy of these creatures, so could someone enlighten me as to if the tongue fact is true or not? Googlemeister (talk) 16:07, 28 July 2010 (UTC)[reply]
It is partially true. First, it is not true of "all" woodpeckers. Some have evolved different means of storing their long tongues. Second, the reason could be just for storage. It may have nothing to do with protecting their brain. -- kainaw™16:27, 28 July 2010 (UTC)[reply]
It hardly seems to have anything to do with "protecting the brain", otherwise there would also be structures at the front of the head. The line in the article is wrong. Physchim62(talk)17:20, 28 July 2010 (UTC)[reply]
on an "evolutionary" note, I find it completely implausible that this arrangement could have "evolved" in five generations. this would be like having your grandkid's grandkids suddenly all sprouting penises that go all the way around their butts to give them a cushion to sit on in school and at their desks. evolutionary biologists just have absolutely no proposed mechanisms that could account for this development in five generations. 92.229.14.166 (talk) 16:45, 28 July 2010 (UTC)[reply]
No - it's totally impossible for 5 generations to do it. The population of these birds is declining - not increasing - so the average number of baby woodpeckers raised to maturity by a breeding pair over their lifespans MUST be less than two. So if some mutation happened - all at once (meaning, probably a single gene changed) in a particular bird - and if it's offspring out-bred birds without the gene 4:1 (so birds with the gene had, on average, 8 successful offspring rather than the more usual 2) and if the gene were passed perfectly onto 50% of the next generation then there could be 4x4x4x4x4 birds with the mutant tongue gene today. Sadly, that's only just over 1000 birds. So even with such crazily optimistic assumptions, there is no way that the entire species could have gotten this change in just 5 generations! Changes like this require many, many changes to the genome - each making a small difference to the survival of the birds (a few percent improvement, maybe, per gene change) - the spreading of that gene is slow - it's gotta take hundreds of generations. Worse still, you have to ask yourself - how are the birds that DON'T have the gene surviving without smashing their brains out? Since the species has been around for a long time - they would already have evolved an adequate means to avoid problems. Only some kind of a change of habitat (like maybe the trees that they inhabit are getting harder) could explain this. SteveBaker (talk) 19:34, 28 July 2010 (UTC)[reply]
Where is this "five generation" thing coming from? I see nothing that claims the tongues on anything evolved in five generations. -- kainaw™17:39, 28 July 2010 (UTC)[reply]
If you mean that it evolved in the some one hundred million years birds have been around, well, that's a lot more credible now, isn't it? 92.229.14.166 (talk) 18:44, 28 July 2010 (UTC)[reply]
It would be after then, analysing woodpeckers with this feature and closely related birds without this sort of feature and trying to determine how old the last common ancestor is would give some clue. As with Kainaw, I have no idea where this five generations thing came from, and you were the one to bring it up. Even for a young earth creationist, it makes little sense since five generations of woodpeckers is probably like 10? years ago. If it evolved in five generations and didn't exist 10 years ago we wouldn't even be discussing this since it would be another example of evolution creationists like to ignore. Nil Einne (talk) 19:26, 28 July 2010 (UTC)[reply]
Yes. Yes, it is more credible. So ... Was this some ham-fisted attempt to say "If something is ridiculous in ten years then it must also be ridiculous in ten million years?", I hope not, not only because that is seriously flawed thinking, (Try applying it to continental drift, erosion, or building the great wall of china.) but because it means you were intentionally trying to muck up someone's question with a debate. APL (talk) 20:18, 28 July 2010 (UTC)[reply]
I now realise 98.229 is not Chemicalinterest or one of his/her sisters which I had initially thought so is perhaps not a YEC although I still don't understand where the 5 generations thing came in to it from. BTW SB is right that it's impossible for it to happen in 5 generations, I didn't mean to suggest it was possible, just that suggesting it happened in 5 generations makes little sense no matter how unusual your world view. Nil Einne (talk) 07:35, 29 July 2010 (UTC)[reply]
When I first responded I mistakenly thought 98.229 was you or one of your sisters (and therefore a young earth creationist) as the IP looked similar to your IP and their comments sounded a bit like what you would say in a topic you've been active in recently. Nil Einne (talk) 16:47, 29 July 2010 (UTC)[reply]
Wow — I don't really understand it either. It's either a restating of rather basic GR principles in a very stilted, technical style, or it is trying to be a very technical digression/exposition. In either case, it is not written clearly, or encyclopedically, at all, and it assumes far too high level of an audience understanding of the concepts to be very useful to most readers. It should be rewritten, at the very least. Other sections are much more clear, even when discussing complicated or technical aspects of the theory. --Mr.98 (talk) 19:01, 28 July 2010 (UTC)[reply]
I agree, it's too complicated for someone that hasn't studied at least some maths at university to understand. I haven't read through it fully, so I'm not sure how much of it ought to be included in the article. Some aspects of GR can't really be explained to the layman (not without simplifying it to the point of it being wrong), but those parts are probably not appropriate for an encyclopaedia. At the very least, it should be split out into a separate article. --Tango (talk) 19:39, 28 July 2010 (UTC)[reply]
Right, that's more what I was trying to convey. It's not that Wikipedia can't contain technical information only understandable to experts, but these should be "drilled down" a bit, not part of a general overview. Some of the concepts it appears to explain can certainly be done in more straightforward, non-technical language, like the equivalence principle, or the fact that GR is SR+gravity, or that light cones are important, etc. --Mr.98 (talk) 20:49, 28 July 2010 (UTC)[reply]
The article is giving a description of what is the meaning of the equivalence principle using a language that can only be understood by readers that have some experience with riemannian geometry. Dauto (talk) 18:31, 29 July 2010 (UTC)[reply]
30% hydrogen peroxide...usually by weight or volume?
Sorry for this question -- it's kind of urgent-- googling doesn't help me. The particular catalog number I'm looking at is H325-500 (Fisher Scientific). Do people usually sell these things by weight or volume? I have to make a 200 micromolar solution of H2O2 in liquid HeLa cell culture media. I've calculated I need about 0.00465 microlitres of pure hydrogen peroxide per every mL of cell culture, but don't know how much 30% H2O2 to add. I figure I can ignore the 70% water in the Fisher stock solution, either way? John Riemann Soong (talk) 16:42, 28 July 2010 (UTC)[reply]
These guys say by weight. But it doesn't matter - it decays and won't stay at 30% once you get it, the decay rate depends on temperature, how often the bottle was opened, light, shaking, etc. I think you should be able to measure the percent content by measuring the density, since H2O2 is much more dense than water (1.44 g/cm^3). (It will decay while you are working with it, so work fast, avoid shaking it, and avoid catalysts.) Ariel. (talk) 17:00, 28 July 2010 (UTC)[reply]
My mass balance says 1.13 g/mL. (I truncated the extra digits since I probably got some latex dust on there.) Ummm, I'm really embarrassed to ask this, but how do I back calculate a weighted average? I knew how to do this! Once! John Riemann Soong (talk) 17:36, 28 July 2010 (UTC)[reply]
water = 1.00g/mL, H2O2 = 1.44g/mL, mixture = 1.13g/mL, x = percent H2O2
I think CRC Handbook has a quick-lookup table (per "Viscosity and Density of Concentrated Hydroxide Solutions" new-feature listed in the ad for it in my recycling bin:). DMacks (talk) 17:45, 28 July 2010 (UTC)[reply]
OK thanks guys. I'm basically following a protocol outlined here, except using a549 cells and not astrocytes. H2O2 shouldn't oxidise the nutrients in cell culture media...right? Well I mean, it will probably do it to some extent, but when I make 200 micromolar H2O2 in cell culture media, most of it should remain unconsumed for 2 hours, right? John Riemann Soong (talk) 18:10, 28 July 2010 (UTC)[reply]
Different sources describe this as being built from either "local pink sandstone" [8] or "local limestone" [9][10]
I can't tell the difference from a photograph at 1km away.. Can anyone else? Also is it possible that it is made of both - in which case would either be more likely to be used as quoins/dressing. Also not to be confused with "Smardale viaduct" which is different. Thanks.87.102.76.166 (talk) 19:14, 28 July 2010 (UTC)[reply]
I would trust the nvt.org websites info over others, since this is their project. Also the stone doesn't look pink to me. Ariel. (talk) 19:28, 28 July 2010 (UTC)[reply]
do you have enough calories to get to the moon? (or: how fat do you have to be)
this is a purely armchair, arithmetic question: does a person have enough joules on their person to escape Earth's gravity and propel themselves to the moon. If not, how fat would a person have to be (at 3500 Calories per pound of fat) to have enough joules on their person for such a journey? This is just a classical physics armchair arithmetic problem, no need to include the usage of any equipment at all... —Preceding unsigned comment added by 92.229.14.166 (talk) 22:01, 28 July 2010 (UTC)[reply]
Earth's escape velocity is about 11.2 kilometers per second; you'll need just shy of that amount of kinetic energy to get over the slightly smaller barrier between the Earth and the Moon. In round figures, that's about 50 megajoules per kilogram. The energy content of fat is (as noted) about 3500 Calories per pound, which runs to (roughly) 40 kilojoules per kilogram. Back of the envelope says that if you were able to instantaneously convert all of the body's fat to kinetic energy and impart that to the non-fat body bits, you'd have to be a bit more than 99.9% fat. (Assuming I've not lost some orders of magnitude anywhere.) The problem gets even worse if you try to burn fat continuously on the way up, because then at least some of the energy goes into lifting fat that will later be burned. TenOfAllTrades(talk) 22:16, 28 July 2010 (UTC)[reply]
It doesn't work. Sorry. (Unless I did my math wrong.)
v = 25010 mph (escape velocity)
e = 1/2 mv^2 (energy)
e = m*38 MJ/kg (energy from fat)
m = x lb (x is the unknown amount of fat)
x lb*38 MJ/kg > 1/2 * x lb * (25010 mph)^2 (substitute variables, and note that it's an inequality)
solve for x. Result: x < 0. Meaning it doesn't work.
BIG NOTE: This is assuming you are lifting all the fat into orbit. Which you may or may not be doing depending on how you burn the fat. Ariel. (talk) 22:30, 28 July 2010 (UTC)[reply]
If we assume a person weighs m without any fat, and we need to get them to 11.2 km/s, that's about m*6.3 x107 J/kg. That's about 1.5 x104 kcal/kg, and fat stores about 9000 kcal/kg so that's about 1.6*m of fat. If you could burn it all instantly and convert 100% efficiently into kinetic energy then you could escape Earth. So if a person weighed 50kg without fat, they would need about 83kg of fat. Rckrone (talk) 22:37, 28 July 2010 (UTC)[reply]
As Rckrone mentioned, if you don't carry any the fat with you (i.e. you burn it all at once), then it's possible (but note a real rocket does not do that). For a 150lb person it's: 246.716lb of fat. Ariel. (talk) 22:41, 28 July 2010 (UTC)[reply]
Climbing a ladder would mean that you are consuming fat via your cell processes, not actually releasing all of its energy in a theoretical situation. Since cell processes aren't 100% efficient, it may take more energy (please correct me if I'm wrong). --Chemicalinterest (talk) 11:03, 29 July 2010 (UTC)[reply]
Plus in the ladder climbing scenario, you would starve to death before reaching the moon since it would take years to climb that ladder, and you have baseline metabolism robbing you of energy. Googlemeister (talk) 12:46, 29 July 2010 (UTC)[reply]
Well let's say you have exceptional climbing ability. What I meant to ask is -- since you're relying on a normal force pushing you back, you don't need to reach escape velocity. Does that save energy, or no? John Riemann Soong (talk) 13:21, 29 July 2010 (UTC)[reply]
If the earth did not rotate then it doesn't help at all - you could climb to the top, but to actually reach the moon you need the same total energy as the escape velocity. And escape velocity takes into account the energy of climbing out of gravity. But the earth does rotate, so by climbing up a ladder you allow the earth to spin you, if the ladder is long enough to reach geosynchronous orbit then the earth provides most of the energy you need. You just need enough to climb up against gravity. Ariel. (talk) 16:31, 29 July 2010 (UTC)[reply]
Looked at another way, how much matter, in the form of fat, if converted to energy, would be needed to propel a 100 kg person to the moon, if E = MC2? Edison (talk) 05:08, 30 July 2010 (UTC)[reply]
There is no practical way to get a hydrocarbon, let alone cellulite, to undergo the kind of nuclear reaction that would release even a small amount of energy in this way; and there definitely is no practical way to annihilate the entire fat molecule either to convert its entire mass to energy; so if this is strictly a gedanken-experiment, the fact that you are using "fat" as the mass to be converted to energy is irrelevant. Nimur (talk) 05:16, 30 July 2010 (UTC)[reply]
To accelerate 100kg to the escape velocity of the earth will require the energy in 69.54 micrograms (6.954x10^-5 g) of matter - any matter, not just fat. Ariel. (talk) 05:22, 30 July 2010 (UTC)[reply]
The potential energy increases from -63 MJ/kg at Earth to -4 MJ/kg at the Moon (-1 MJ/kg w.r.t. Earth, and -3 MJ/kg w.r.t. the Moon), so with constant mass it is an increase of 59 MJ/kg. If fat is burned instantly the amount needed is 59 / 38 = 1.55 times the mass of the payload, and to infinity 63 / 38 = 1.66 times the mass of the payload (the 1.6*m already mentioned above). Ignoring the rotation of Earth, for climbing the ladder with 100 % efficiency while burning fat it seems we have a mass reduction by a factor e for every increase of the potential field by 38 MJ/kg, so to infinity mass is reduced by a factor e ^ 1.66 = 5.3. For a ladder to the Moon we have to climb to the point where we start descending. From there we can recover energy with suitable equipment, but to convert that back to body fat requires some material to be found along the way.--Patrick (talk) 09:22, 30 July 2010 (UTC)[reply]
Check you understand or already know Fleming's left hand rule for motors and Fleming's right hand rule. Because the ions are moving that's like an electric current - big clue - the positive and negative ions moving in the same direction are like currents in opposite directions. I'll give more info. if you are still stuck. (also remember that the direction of the electric current is from positive part to negative part) Sf5xeplus (talk) 23:23, 28 July 2010 (UTC)[reply]
It's the second part of the question that I can't do (part (ii) i.e. the direction of the current through the voltmeter), not the first part (part (i)).115.178.29.142 (talk) 00:11, 29 July 2010 (UTC)[reply]
Huh? The second part is the simple bit, if you can do the first part! Maybe if you read our small section on conventional current, you will see the answer (the question is asking if you know what conventional current is). Physchim62(talk)04:05, 29 July 2010 (UTC)[reply]
can you tell just by the honk whether a man or woman is blowing their nose?
How about you, can you do it? Is this a poll? Some people are presumably better than others at this sort of thing. I probably could tell a child, but not the difference between a man and a woman. Is this really a serious question? Ariel. (talk) 22:48, 28 July 2010 (UTC)[reply]
obviously by "can you" I mean "can one". I was thinking by analogy with voice (clearly different for males and females, very few voices are hard to tell which), due to anatomical differnces. In some ways there is anatomical similarity with honk production, namely lungs are also involved. where is honk produced? in the nose, presumably. so, again, would men have larger or more cavernous noses on average? Anyway these are just possibilities, the answer could be "unlike voice, there is no discernible difference between male and female honk". But I would like to know your reasoning if that is your answer. 92.229.14.166 (talk) 23:20, 28 July 2010 (UTC)[reply]
It's really hard to believe that anyone would study such a strange matter - so it's unlikely that we'll find a good answer for you. SteveBaker (talk) 02:18, 29 July 2010 (UTC)[reply]
I agree that it is most unlikely that any definitive answer is available, but I would put my money on the answer being "no" (discounting the fact that, in many cultures, women find it less acceptable to blow their noses loudly). Perhaps an ENT specialist would know about anatomical differences (if any) between genders, but I suspect that variability within each gender completely swamps any slight gender difference. Is there a significant difference in head size between genders? Dbfirs07:03, 29 July 2010 (UTC)[reply]
"one of the great controversies, that of preformation versus epigenesis and this was settled primarily by reference to chick development. The preformationists thought that the entire individual was present in miniature in the egg or, alternatively, within the sperm and that it simply grew until it hatched; there was thought to be no differentiation, merely growth. The epigeneticists considered that both growth and differentiation were involved and were necessary. Today, we are all epigeneticists."
The roots epigenesis (biology) and epigenetics are clearly different in meaning; "epigenesis" applies to a theory of developmental embryology and "epigenetics" relates, in a very general sense, to structural changes that control the expression of genes (though interestingly quite important in regulating embryogenesis). I suppose one could call a scientist who studies epigenetics to be an epigeneticist, but I don't hear that term used very much. Given that preformation has been soundly debunked in favor of a complex developmental process resembling epigenesis, the author of your quote is presumably saying that there is no one left who still thinks preformation is a viable theory. Maybe he or she thought the term "epigeneticist" was just better than "epigenesisicist". --- Medical geneticist (talk) 23:32, 28 July 2010 (UTC)[reply]
We are all epigeneticists if you are using the terms of the 19th century embryological debates — we do believe that development is crucial, and even the most hard-line hereditarians do not believe in the preformation hypothesis in the terms it was believed in the 19th century. We are not all epigeneticists if you are using the term as it came into usage in the late 20th century as applied in the term "epigenetics". Personally I think it is a misleading phrase — a more accurate way to put it would be to say that we are no longer preformationists. (What we "are" here is more defined by the negative by the positive, because we don't really believe everything the 19th century "epigeneticists" believed, I am sure.) --Mr.98 (talk) 01:16, 29 July 2010 (UTC)[reply]
When everyone takes the same label - there is no need to use the label anymore because it loses all linguistic value. There used to be heliocentricists and geocentricists (those who believed the sun was at the center of the solar system and those who believed the earth was at the center) - but now that we are all heliocentricists, we don't need to use the word anymore. That doesn't make the use of the word incorrect - but rather just obsolete. SteveBaker (talk) 02:16, 29 July 2010 (UTC)[reply]
I don't think it's quite true that the word is obsolete if the position is debunked. We still want to be able to talk about the historical debate. Rckrone (talk) 05:27, 29 July 2010 (UTC)[reply]
True, but we also need to be careful about our use of terms: probably everyone on this page accepts that there are things called "atoms", but that doesn't make us "atomists" in the sense of Ancient Greek philosophy! Physchim62(talk)06:50, 29 July 2010 (UTC)[reply]
But we're not really heliocentrists — we don't believe the sun is at the center of the universe, which was what the original heliocentrists believed (see Heliocentrism). That's kind of my point — we actually don't subscribe to the beliefs of the "winning" group so much as we have repudiated the beliefs of the "losing" group. It's not that we all became heliocentrists, but rather that we are simply not geocentrists. The nature of this kind of scientific change (if one can generalize it) is not so much that we all switch to some winning view, but we go away from the losing view, and a whole new set up complicated views opens up. It is more accurate to just say that nobody (to a rough approximation) believes the old view anymore, rather than saying that everybody believes the new view (which is a vast oversimplification). --Mr.98 (talk) 13:36, 29 July 2010 (UTC)[reply]
Sun Exposure, Skin Cancer and Vitamin D
I read a New York Times article about how being outside, minimally clothed and unprotected by sunscreen, is an excellent way for one to acquire his healthy dose of Vitamin D. I have also been told for my entire life that doing these things will give me sunburns and horrible skin cancer. I would like to believe that the NYT version is true, because I wouldn't need to worry about sunscreen anymore. Is there a dermatologist in the house? Can anyone sort this out for me? Thanks. Postprehistoric (talk) 23:31, 28 July 2010 (UTC)[reply]
you could try Risks and benefits of sun exposure which quotes from a study "there is not enough information to determine a safe level of sun exposure at this time" ,, also "Despite the importance of the sun to vitamin D synthesis, it is prudent to limit exposure of skin to sunlight". You also still would want to avoid sunburn for all the reasons. 87.102.76.166 (talk) 23:52, 28 July 2010 (UTC)[reply]
My understanding is that vitamin D can prevent skin cancer, but it only takes 15-20 minutes to max out the vitamin D production, anything more than that is not necessary. See also Sunburn#Controversy over sunscreen and Sunscreen controversy. Sunscreen might not help at all. If you do use it I would pick one with titanium dioxide or zinc oxide, because they are considered far more effective at preventing real damage (as opposed to reddening, which all kinds prevent). This subject has massive debate going on right now, no one can give you a definitive answer. Some studies even show that using sunscreen actually increases the risk of melanoma. The only thing (I think) everyone agrees with is: Get less sun and take vitamin D supplements instead. (But simply less sun without vitamin D might be worse than more sun.) Ariel. (talk) 00:21, 29 July 2010 (UTC)[reply]
I don't have a reference to hand, but apparently you can get enough vitamin D by spending about 10 minutes outside on an overcast day with just your face and arms bare. In fact, you can get enough vitamin D just from eating a balanced diet without any sunlight. So, in short, don't worry about vitamin D. (This is all assuming you are reasonably fair skinned. If you black and live somewhere at reasonably high latitude, then vitamin D can be more of an issue.) --Tango (talk) 00:36, 29 July 2010 (UTC)[reply]
It isn't a question of getting enough vitamin D. Vitamin D is a powerful antioxidant, and there is reason to think that high levels of it may have a protective effect against cancer. But that's based on theory and isn't backed up by much actual evidence, one way or the other. Looie496 (talk) 00:41, 29 July 2010 (UTC)[reply]
About vitamin D, I think the evidence now strongly points in the direction to the recommended levels of intake being way too low, the optimal levels being so high that it even exceed the current official maximum safe dose. It takes time for the health officials to update the recommended dose, but as this article points out, the expert themselves are using vitamin D supplements themselves at levels they think are healthy which is of the order of 5,000 IU per day.
One has to note that a vitamin D dose of the order of 10,000 IU per day is entirely natural, it cannot be compared to e.g. taking a high vitamin C dose that you can only get that from supplements. E.g. bushmen in Africa don't wear much clothes and hunt for meat during the day for hours when the UV index can be as high as 12. They then get a dose of 10,000 to 20,000 IU of vitamin D and not much more than that, because of a dynamical equilibrium between vitamin D synthesis in the skin due to UV radiation and vitamin D being broken down by UV radiation. To get an overdose of vitamin D you need to take 100,000 IU every day for several weeks.
Since the 17th century more and more people have been living and working indoors causing extremely low vitamin D levels leading to problems with calcium absorpion from food. To prevent this, you only need to take very low doses of vitamin D, a few hundred IU per day is enough. This is what the current recommendation is based on. But new evidence suggests that this is low dose is similar to the miniscule dose of vitamin C you would need to take to prevent scurvy.
If we had all stopped eating fresh vegetables and fruits millennia ago and getting the minimum amount of vitamin C to prevent getting scurvy, we may well have set the recommended dose of vitamin C to be a lot less than found in a single apple and one apple would perhaps be the maximum safe dose as there would not have been the rigorous medical evidence that eating several pieces of fruit per day does not cause some unknown horrible illness many year later. This logic would set the officially recommended dose but, of course, the experts in the field would know that from a more reasonable point of view this is all nonsense and there would likely be evidence that a higher dose is actually beneficial. What you would see is that the experts themselves would not stick to the official guidelines, which is exactly what is happening in case of vitamin D.
According to this chart (in the Jet Engine article) a turbojet will be more efficient (measured in Isp) than a turbofan starting at about Mach 1.5. I suspect this is because the turbojet will have a higher average exhaust velocity than the turbofan. A turbofan exhausts a large volume of lower velocity air, but since the thrust has to do with the difference between airspeed and exhaust velocity, the lower exhaust velocity means lower thrust at a high airspeed. The turbojet exhausts a smaller volume of high velocity air, so it maintains higher thrust at a high airspeed.
For these purposes, you can think of a turbojet as a low-efficiency turbofan - so on that chart, they will lie just below turbofans. For example, the engine that powered the infamous Concorde will have an Isp of around 3000 s at cruising speeds (just over Mach 1). You can verify this for yourself by converting the thrust specific fuel consumption in to specific impulse (the equations are given in our article for a variety of units). In this case, Olympus 593 engines have a SFC of ~1.2 lb/lbf·h - so convert by (3600/1.12), yielding Isp around 3000 s at cruise speed of Mach 1. In reality, the distinction between a turbofan and a turbojet is a semi-subjective distinction about what counts as "low pressure" bypass. There are many engines that could pass for either description. Compare the cartoon diagrams of turbofans to turbojets - as you can see, the big difference is expansion ratio of the bypass flow - and there is not a clear demarcating line between the two. In the extreme case, of course, we can clearly see that a large amount of ducted air is not "jet-like", and you can keep making the bypass ratio higher and higher... at some point you stop bothering with a nacelle and end up with an unducted turboprop (even more efficient! but much slower). Nimur (talk) 03:50, 29 July 2010 (UTC)[reply]
What is the lightest/least dense non-porous solid?
Lithium is the lightest element that's solid at room temperature at 0.53 g/cm3. I don't know whether there are any less dense compounds out there - but I suspect not. SteveBaker (talk) 02:02, 29 July 2010 (UTC)[reply]
If we can freeze non-solid-at-RT things, solid hydrogen I think is probably around 0.07 g/cm3. Or at least that's what hydrogen says the liquid is at the melting-point, so probably close? The article specifically about the solid has few physical properties. DMacks (talk) 02:38, 29 July 2010 (UTC)[reply]
For this one, we might have to define "porous". Everything would have exactly the same density if it were not for the void-spaces. It just so happens that some solid materials have void-spaces on molecular scales that are defined by crystal lattices; some solid materials have void-spaces on macro-crystalline or polycrystalline scales; some solid materials have void-spaces that are large enough to be filled by air or gas; and so on. One could conceivably build a sturdy steel shell and pump out the air from its interior: would it be fair to call that a low-density material? After all, there would be nothing but steel in it; nothing would be "diluting" its volume or mass. And it wouldn't really be porous. How small of a pore is required before you call a material "nonporous?" Nimur (talk) 04:05, 29 July 2010 (UTC)[reply]
It should also be noted that an aerogel is not a material per se. It is a colloid; which is to say it is a type of mixture. As a mixture, it is a combination of multiple materials; aerogel being a mixture of the solid matrix and air. The density of a mixture is dependent not only on the properties of the components, but the proportions in which they are mixed. Pure substances generally have well-defined densities, for example look at the infobox of iron or or sodium chloride or sucrose. However, not being a pure substance, one cannot define a specific density for aerogel in general, only for specific formulations of aerogel. --Jayron3206:42, 29 July 2010 (UTC)[reply]
If you could get enough Di-positronium together and crystallize it you would get something about 1000 times less dense than solid hydrogen. However it is too radioactive with too short a life for this to happen in our current technology. Graeme Bartlett (talk) 10:23, 30 July 2010 (UTC)[reply]
A trip to any reasonably-sized airport would disprove "Airport Runways are built in one direction". And even single-strip airparks would be likely to disprove "Are they built East-West?". They're built at whatever directions space allows and that is viable for prevailing weather conditions. Our runway article talks about it in a whole section about orientation. Airplanes care a lot about wind, which can blow in any arbitrary direction regardless of the earth' rotation, though there may be some places that almost always have wind in a certain direction. Weather systems are certainly affected by the earth's rotation on a large scale, but not "rotation -> that's how the breeze goes in general". Rockets and other things that are not relying on air motion for their own motion and that need to move in a certain direction relative to the earth could rely on the rotational boost. DMacks (talk) 02:29, 29 July 2010 (UTC)[reply]
Right. Most places have a prevailing wind, actually, and airplanes can take off and land more easily facing into the wind than facing with it or sideways to it. Looie496 (talk) 03:44, 29 July 2010 (UTC)[reply]
I'm a pilot, and I can assure you that there is no set way that a runway must be oriented. DMacks, Looie496, and HiLo48 are all correct. They are built with the local environment, "normal" winds, etc in mind. Not all runways are the same. Some have [slight] hills in them, so they have a pronounced dip or crest in the middle, some are longer, some are shorter, some are wider, some are narrower, some can handle more weight, and there are some where you take off and land in one direction because there's a mountain on one end. It really depends almost entirely on what the runway is to be used for and where it is. Falconusptc05:06, 29 July 2010 (UTC)[reply]
Indeed. The airfield just down the road from me (LEIG) is planning on extending the runway: the main consideration was where they could buy the land from (although it's also one of those one-way runways with a biggish hill at one end). Physchim62(talk)05:30, 29 July 2010 (UTC)[reply]
Other then what's already been said, I think the consequences of the flightpath the runway will impose will also get consideration. For example a runway which means the planes will be largely taking off over water or flat, uninhabited land would generally be preferred over one which results in planes over taking off or landing over houses (meaning when height is not a concern) not just for safety reasons but because planes tend to be noisy particularly when low flying Nil Einne (talk) 07:27, 29 July 2010 (UTC)[reply]
Dear Sir, i have a fiat car wit me some days back its stop working , some engineer came and said some one is putted cut in the main network line(CAN Network) bcoz of that its stop start working,now they have rectify that error.Now i want to know that whether dis cut can produce any error in future nd what kind of cut should i make in the networking so that my sub woofer(Amplifier) work properly .
The CAN-bus is an automotive network technology. Think USB for a car and it's a close approximation. As such, the repair shouldn't lead to errors down the line. Presumably they replaced a cable and, unless that cable is cut again, that's not a part that's likely to fail any more than USB cables go bad (which is to say, rarely). Of course, a future cut would produce the same problems. As for the subwoofer, as far as I know, car stereos don't use CAN-bus to carry audio signals. They'd be analog speaker wire rather than digital CAN-bus. — Lomn03:54, 29 July 2010 (UTC)[reply]
I'm wondering if the person who installed the subwoofer cut the CAN bus wire, thinking it was the audio line and trying to re-route it to the subwoofer amplifier. In that case, you should make them pay for any repairs necessary. Nobody should have touched your CAN bus to install an amplifier. If the CAN bus is damaged, depending on your particular FIAT model, there may be serious safety concerns operating the vehicle - some engine control units and safety features like brake or airbag controllers may use the CAN for communication. Most cars have a separate CAN bus for critical vehicle systems and "passenger-compartment" things like radios and DVD players; but the information provided is insufficient to know what has been cut. Have a mechanic you can trust analyze the problem, and make whomever cut the wire pay for it. Nimur (talk) 04:13, 29 July 2010 (UTC)[reply]
why do stocks prices move during the day even when there is no new information!
why is it that even in boring times with no new information, multibillion dollar companies' stock prices fluctuate at least a few percentage points continuously every second or few, all day, every day? For me, it would make more sense for them to stay in a flat line for a few day (or hours, if a piece of news comes unexpectedly) then jump to the new price based on the new information and stay in a flat line until it jumps to a new price due to the next piece of news. But this never, ever, ever happens even within a single day (for the largest companies) let alone for days or weeks. Why is that? You don't get a different price at the gas station every fifth of a second, why do you on the stock market? 84.153.183.42 (talk) 16:31, 29 July 2010 (UTC)[reply]
The price does not depend only on the single company, it also depends on the industry group. It also depends on the relative risk between that company and other companies, and between that company and bonds. So other things change, which causes a relative change, which moves the price, i.e. other stuff might suddenly be slightly better or worse. Ariel. (talk) 16:37, 29 July 2010 (UTC)[reply]
so? Information changes in the real world second by second, but the gas price isn't updated at the pump that fast. What's the difference? 84.153.183.42 (talk) 16:39, 29 July 2010 (UTC)[reply]
There isn't a single, efficient market for gas, there are lots of different gas stations. If I want to buy a share in a company, I will buy the cheapest share on offer. If I want to fill my gas tank, I go to the most convenient gas station and pay whatever they are charging (within reason). --Tango (talk) 16:46, 29 July 2010 (UTC)[reply]
Gas prices do actually change every second, it's just the gas stations refuse to adjust the price because it would make people nuts. They do earn and loose money on the changes! They hate volatility for this reason. It's even worse for them - they may buy a truck full of gas for a high price, and the next day prices are lower, and they loose money on all the gas they are storing. And they reverse too, and they hope it works out long term. Ariel. (talk) 17:00, 29 July 2010 (UTC)[reply]
Yeah, the price is determined by what people have recently traded it for. When the price fluctuates that means there have been trades and since different people have slightly different ideas about what the stock is worth the price will change. What people are paying in turn affects what other people think about the value. There is also new information all the time in the sense that lots of things can subtly affect the market and people are working very hard to analyze the incoming data and update their valuations. When the stock of some other company goes up, when a new trade agreement gets signed, when a new oil reserve is discovered, that can affect the value, even if the company has little to do with these other industries. There are things happening in the world all the time. Rckrone (talk) 17:13, 29 July 2010 (UTC)[reply]
Yes. Reported stock prices are snapshots of continual trading activities. The only way to get a prolonged flat "noise free" price would be for nobody to trade in that stock. Gas (petrol) stations that have electronic price displays can use them to play "gotcha" knowing that different market segments refuel at characteristic times e.g. commercial vehicles on weekdays, private vehicles at weekends. However changing the retail price too often would be counterproductive as bad PR. Cuddlyable3 (talk) 17:31, 29 July 2010 (UTC)[reply]
Also, consider some investor who holds 10,000 shares of BoringCo. It has had no news for a month and will have no news for another month. But that investor is also investing in and monitoring ExcitingCo, which you can find 20 news stories on every day. When news on ExcitingCo makes the investor think the shares are going to go up, he may sell 5,000 of his BoringCo shares to invest the money in ExcitingCo instead; and when ExcitingCo announces all their iPads are overheating, the investor may dump it all and invest the money back in safe old BoringCo. Multiply this by many investors and there's plenty of price fluctuation, though all this buying and selling of BoringCo has nothing really to do with news coming out of BoringCo. Comet Tuttle (talk) 18:08, 29 July 2010 (UTC)[reply]
This is really a question about human behaviour related to financial greed. That also applies where computers are assisting because humans have programmed the computers. It's all about people trying to gain the tiniest advantage, and then gain financially from it by multiplying that tiny advantage thousands of times. HiLo48 (talk) 19:49, 29 July 2010 (UTC)[reply]
Dog repellent
I need to keep dogs away from a part (not very large) of my garden and I'd like to find out if there are some substaces whose smell acts like a deterrent/repellent for them. Obviously not something armful. The best would be a "homemade" substance relatively odourless for humans but as disgusting as possible for dogs. --151.51.156.20 (talk) 18:27, 29 July 2010 (UTC)[reply]
Suggestions I've heard include lemon slices, or ammonia, but the latter can make it pretty unpleasant for humans too. And I've had a beagle that decided he liked to eat citrus fruit, along with the million other things beagles typically found attractive. It can depend on the breed of dog, and what it is in that part of your gardent that could attract them. Scent hounds can be attracted to something that seems heavenly to them but quite unobservable by humans. Any human created product has to overcome a scent we can't even detect, quite a big ask. A bit of trial and error may be needed. Can't do a wire fence? HiLo48 (talk) 19:59, 29 July 2010 (UTC)[reply]
If the pressure of the atmosphere gradually increased to double its normal pressure within a day, what would be the effects on human life and industry? --Chemicalinterest (talk) 20:36, 29 July 2010 (UTC)[reply]
I think it would still be safe to breath, SCUBA divers breath standard air at that pressure all the time.
The boiling point of water would go up by about 30 degrees C. So your spaghetti would cook a lot faster.
Fires would probably burn hotter and stronger with twice as much oxygen per unit volume of air. You can imagine that both these things would effect large industrial processes like power generation. Not all of them would be able to adapt. APL (talk) 21:10, 29 July 2010 (UTC)[reply]
True, but, as mountains go, Everest is apparently quite an easy one to climb. You can basically walk up most of it. The cold, wind and lack of oxygen are the main problems, rather than the physical act of climbing that high. --Tango (talk) 00:15, 30 July 2010 (UTC)[reply]
You'd need to put more helium in your Zeppelin, but once you did that it would have greater carrying capacity. APL (talk) 22:14, 29 July 2010 (UTC)[reply]
You'd get a lot more horsepower out of your car too - no need for a turbocharger! But even if humans could endure that - I'm sure that there would be abrupt and spectacular decline in animal and plant populations for one reason or another. It's hard to predict exactly what all of the details might be but I would guess that forest fires would be much more common - and insanely difficult to control, more gasses would dissolve into the oceans - and that could change their pH and cause all manner of other nastiness for oceanic life. It's pretty certain that it would lead to total disaster of one kind or another within a matter of months. SteveBaker (talk) 22:25, 29 July 2010 (UTC)[reply]
Be sure to check your tire pressure before trying out your new-found horsepower! You'll find it's nearly 15psi lower than it should be. APL (talk) 00:04, 30 July 2010 (UTC)[reply]
Not overnight, but eventually you'd get really big bugs. Most insects rely on diffusion (rather than an active circulatory system) to provide oxygen to their tissues and this is a key factor in determining their maximum sustainable size. Increasing the pressure of oxygen will allow insects to evolve large sizes. Dragons flight (talk) 22:43, 29 July 2010 (UTC)[reply]
As evidenced by the giant insect fossils found from times in the Earth's past where the proportion of oxygen was much higher, eg. the Meganeura. Not all scientists agree about the role of higher oxygen in allowing large insects to survive, though. (That article gives some details.) --Tango (talk) 00:15, 30 July 2010 (UTC)[reply]
Major changes in weather and climate. The amount of solar heat escaping to space would be greatly reduced, so the Earth would get quite a bit hotter and wouldn't cool nearly as much at night. Looie496 (talk) 00:13, 30 July 2010 (UTC)[reply]
Surely it's not phagocytosis right? These are lung cancer a549 cells, not white blood cells. (Watch the gold particle in the upper left corner of the centre region.)
How many pounds of helium is necessary to support an object with a weight of 200lbs,utilizing one square meter of material filled with the gas?The height of the object is six feet.What type of material should be utilized to constrain the pressure? The apposing force to the object is water.
Thank you
Sincerely,
Tom Ambron
email {email removed} —Preceding unsigned comment added by 75.82.85.84 (talk) 23:08, 29 July 2010 (UTC)[reply]
Do you mean that you wish to construct a balloon with 1 square meter of surface area? This will limit you to a maximum sized balloon based on the surface-area of a sphere (the most efficient volume-to-surface-area structure). If you use a balloon, the necessary consideration is "how many kilograms of helium are needed to inflate the balloon? If the material is inelastic, you can fill it with helium at atmospheric pressure (or the pressure of the water at the depths you are considering). Then you can use the ideal gas law to calculate the mass of helium that will inflate the volume at that pressure. Now the question is whether the resulting density of helium is sufficiently low to provide 200 pounds of buoyant force. I think you need to restate the question - it is not really clear what you're looking for. We can solve all kinds of equations, but when the requirements are unclear, such solutions may be inapplicable. Nimur (talk) 23:33, 29 July 2010 (UTC)[reply]
It's simply not possible. Forget the helium, even the mythical vacuum balloon couldn't do it. If you mean that the balloon is a cubic meter, the displaced air weighs only 2.6 pounds. If you mean that the envelope is made of exactly one square meter of material, then the displaced air is only ¼ pounds! A balloon, no matter what it's filled with, cannot lift more than the weight of the air it has displaced.
You may be of the common misconception that helium has negative weight and that the more you cram into a balloon the lighter it gets, I'm afraid that's not true. Balloon lift comes from buoyancy, the same force that causes boats to float. A common analogy is that wood floats, but if you pile enough wood onto a ship, it will eventually sink. APL (talk) 23:58, 29 July 2010 (UTC)[reply]
No, there is no such particle. Antigravity is firmly in the realm of fiction. As far as exotic matter with negative mass, there is currently no consistent explanation for how such a particle would behave; there is no need for such a particle to play any role in the standard model; and any speculative theories about negative mass or repulsive gravitational force is exactly that - speculative. Nimur (talk) 04:00, 30 July 2010 (UTC)[reply]
I don't understand that bit about water. Are you saying the object is underwater? Helium at above atmospheric pressure would be worse than helium at atmospheric pressure, since there is more helium taking up the same amount of space, so it will weight more while displacing the same amount of air/water. The absolute best buoyancy you could get with 1m2 surface area would be a complete vacuum (you would need a strong container to hold a vacuum, which would therefore be heavy, but let's ignore that and assume a massless container). Such a vacuum-filled container submerged in water would be able to lift the weight of water displaced by the container. As Nimur says, the best shape is a sphere. The surface area of a sphere is and the the volume is . If we substitute A=1 into the first and rearrange, we get . We substitute that into the other formula and we get . That is 94kg or 207lb, so you could just lift your object. If we're using helium at atmospheric pressure, rather than a vacuum (which is wise, due to the weight of material required to cope with the pressure), then we have to minus off the mass of that helium, which is about 16 grams (if I've calculated it right - I expected it to be more, but I don't know why), so not significant. If I misunderstood your mention of water and your object is actually just in air, then you don't stand a chance. --Tango (talk) 00:06, 30 July 2010 (UTC)[reply]
Instead of using the ideal gas law directly, under standard temperature and pressure, one mole of any gas has a volume of just over 22.4 litres. Nitrogen-14 has a molar mass of 28 grams, oxygen-16 is 32 grams, helium-4 (which is mono-atomic) is 4 grams. Therefore air (80% nitrogen, 20% oxygen approx), has a density of 28.8 grams / 22.4 litre. A helium-balloon has a buoyancy of 24.8 grams/22.4litre or 1.1 grams/litre.
As for the water analogy, imagine an (theoretical) advanced life form that lives on the sea bed. Their density is well above that of water, so they can't swim up. If they want to lift an object to the surface of the water then they can attach a balloon to the object. As long as the object+balloon is less dense that water then it will rise. If the balloon is filled with vegetable oil (900grams/litre) then there is 100grams/litre of lift in water. The balloon still has real mass, it's just that the density is less that water, so it will rise.
BTW, a wooden boat, full of wood, will float, but very close to the water. It will act like a solid wooden object. In fact they were used for demining sea areas during WWII, see Naval_mine#Mine_breaking.
I incubated a549 cells in 200 micromolar H2O2 for 90 minutes, washed the cells with fresh media and then observed them under DIC. (The cells had already been incubated in the presence of colloidal gold prior to incubation with H2O2.) The results were rather spectacular: an insane amount of intercellular bridges and connections (on all sorts of levels, criss-crossing everywhere) could be found, compared to situations without hydrogen peroxide. Oh was I happy!
But then 40-60 minutes into the experiment, my cells started dying from the bottom of the slide upwards. It was strange -- normally apoptosis is a stochastic event and is a rather random process that increases in chance as time goes by, but here it was like there was an invisible wave of apoptotic death slowly creeping up the slide. Is it nutrient exhaustion? I am sure I sealed the slide with nail polish to prevent evaporation.
A few papers I found said that H2O2 at 200 micromolar shouldn't decrease the viability of a549 cells too much...but they used 24h assays. Maybe in the time frame of a few hours, the H2O2 kills a lot of cells only to have the really mitogenic ones produce lots of viable ones?
Or maybe they are not apoptotic at all? The normal "apoptosis bubbles" were hard to see -- the entire cytoplasm changes viscosity almost -- it becomes very viscous and the cell's "insides" appear to slow down and look very different. Maybe it's the actin polymerising? I wonder if it's because the hydrogen peroxide is oxidising the colloidal gold, producing lots of Au(III) oxide and at the same time, decreasing the pH since Au(III) seems like a strong Lewis acid. John Riemann Soong (talk) 00:06, 30 July 2010 (UTC)[reply]
Mmm, I didn't see any precipitate, but then again this is colloidal gold, not bulk gold, so Au(I) and Au(III) atoms would remain attached to Au(0) on the nanorod. I believe the sulfide thioether linkages popular for functionalising colloidal gold with are made by having the functionalised thiol precursor bind to the residual Au(I) sites (on an otherwise Au(0) rod) that weren't reduced in the initial manufacture of these nanorods. (Someone correct me if I'm wrong). John Riemann Soong (talk) 13:58, 30 July 2010 (UTC)[reply]
Oh it just hit me. According to the thioether article, they can be oxidised to sulfoxides and sulfones. I do pipette most of the old media (containing the nanorods) before I add the H2O2 but maybe I should do a few buffer rinses first? H2O2 won't react with membrane-bound gold rods inside endosomes in cells, right? Are sulfides bound to Au(I) more reactive or less reactive? Do they become more or less nucleophilic -- I mean, the Au(I) should sap some of the sulfide's nucleophilicity, right? (The linkage looks like: (rod)=Au(I)-S-(short alkyl/polyether chain)-COO-. John Riemann Soong (talk) 14:20, 30 July 2010 (UTC)[reply]
Also, why is the standard half-cell reaction potential for Au(III) + 3e- ---> Au(0) less than the reaction potential given for Au(I) + e- ---> Au(0)? (The latter has a higher potential than the two electron reduction of hydrogen peroxide in the presence of H+). I'm trying to figure out how favourable gold oxidation by hydrogen peroxide is, and I only spent a third of a semester on electrochemistry. John Riemann Soong (talk) 14:28, 30 July 2010 (UTC)[reply]
Because energy and mass both exert gravitational force; in Newtonian physics, mass is used in gravity calculations. The stress energy tensor (hint: read that article) takes energy and momentum into account; remember that according to General Relativity, gravity is a pseudoforce caused by curvature of spacetime. In most layperson explanations of GR gravity, it is explained that large masses curve spacetime, and that gravity is really just objects moving staight (as objects do), but doing so in curved spacetime. However, it turns out that mass is not the value which describes the curvature of spacetime, the stress energy tensor is the relevent value. --Jayron3200:38, 30 July 2010 (UTC)[reply]
Momentum as well will curve space-time? So if we take an a 1kg object, it will curve space-time more if it's moving at 99% the speed of light? ScienceApe (talk) 01:16, 30 July 2010 (UTC)[reply]
Well, yes, but not because of momentum, per se, but because it has more energy, via KE = 1/2 mv2. Well, not exactly, but via the GR equivalent at relativistic speeds near the speed of light. Objects moving at a higher velocity have more energy, and thus curve spacetime more than than those which are stationary. Velocity affects energy, and energy is mass. --Jayron3201:26, 30 July 2010 (UTC)[reply]
How? By inducing a noether current that must be counterbalanced in order to conserve mass/energy/momentum flux. Consequently, some other "thing" needs to either move or change velocity, or else the flux conservation is violated. But Newton tells us that things don't just start "moving" for no reason - we have inertia! A body at rest remains at rest! So, if we want to remain at rest, and also change our momentum, we need to start warping space so that maintaining a constant position yields a change of momentum - ergo, gravitation. The exact geometry of the warping is nontrivial - and requires solutions of the general relativistic equations - but in the simplest case, we see elliptical planetary orbits, - planets that are tracing out an <x,y,z,t> vector path, when in fact all good sense tells us that they should be inertially stationary. Nimur (talk) 04:32, 30 July 2010 (UTC)[reply]
In a bit more details on why the tensor includes momentum; its because there are three fundemental conserved quantities in any physical interaction between bodies: energy, mass, and momentum. This is true even in classical physics. So, when two objects interact, even classically, momentum must be conserved. Even under the Newtonian definition of gravity, as two objects interact with each other gravitationally, their total momentum must remain constant throughout the interaction. Think of it this way. If you are a chunk of space rock flying by the earth; as the earth slows you down by "pulling" on you via gravity, the earth itself must speed up by the exact same amount.
In GR physics, its FAR more complex, and requires some pretty advanced mathematics. However, the law of conservation of momentum still cannot be violated. So, any calculation of gravity must take momentum into account. The stress energy tensor itself is described by a matrix of values. It isn't a single number like "mass". It is a tensor, which is a multi-dimensional quantity. If you know what a vector is, you can think of a tensor as a vector on steroids. Where as a vector quantity has two values (origin and direction), a tensor can have dozens of values, which are manipulated via matricies. The stress energy tensor uses four "types" of values (though there are multiple groups of values for some of the types). There is the "energy density", the "momentum density", the "energy flux" and the "momentum flux". Basically, in order to correctly calculate the effect of gravity within a system, say a simple two-particle system, you need to know a) the mass-energy of each object (energy density) at your initial conditions b) the momentum of each object initially (momentum density) c) the mass-energy changes experienced by each object as they interact (or curve spacetime, whatever your perspective) (energy flux) d) momentum changes experienced by each object as they interact. Now, it is even more complex because each location in the matrix isn't a simple number like "three", but rather a complex polynomial which describes, say, the energy density of the entire system in three dimensions (that is, how much mass-energy is at every point in space in our system). This is of course a gross oversimplification, since you actually have to do the math to get the implications here. I can't do the math myself, really, but this is how I understand it as a layperson. Perhaps someone with a better physics background could fix my errors or explain it better. --Jayron3201:44, 30 July 2010 (UTC)[reply]
And just as an addendum, you may want to read Stress-energy-momentum pseudotensor, which is the actual value used in GR. The stress-energy tensor has other uses, but it is not strictly applicable to GR apparently. Again, I lack the math to understand exactly why, but I do read english, and that's what the article seems to say. --Jayron3202:00, 30 July 2010 (UTC)[reply]
Another way to rephrase Jayron's explanation: the stress energy tensor allows a physicist to describe the gravitational interaction of a body in the form of a matrix that describes all the relevant concepts - energy, momentum, position, and so on, in generalized coordinates. The way that the body behaves depends on the mathematical laws that are expressed as degrees of freedom of the system dynamic. In a simple case, like a ball rolling down a hill, the only relevant degrees of freedom are position (x,y,z); and the respective derivatives with respect to time (velocity in x, y, z). These parameters are constrained by Newton's laws of motion - a set of empirically derived relationships between position, velocity, and acceleration due to gravity. General relativity allows the physicist to consider these relationships in a more general way, (hence "general"); part and partial to this generalization is that the position, velocity, and acceleration must be described only in a relative way, and not with respect to any fixed frame. Now, there are lots of relativistic theories, including some that are classical and consistent with Newton's laws - Galilean relativity, for example. But if you make the theory extremely generalized, you can no longer make the relationships simple: "F = m a" is not a general description of a gravitating system, because Force due to Gravity is a sort of "imagined" quantity that Newton invented. (Sure, it mathematically explains the rate and distance at which the moon circles the earth, but it doesn't do a very good job at explaining why the moon keeps magically changing direction instead of flying off in a straight line). So, general relativity seeks to eliminate that unnecessary invention by reformulating the relationships between the free parameters (position, velocity, mass, energy, and so on). The only sensible way to reformulate those relationships and still describe the kind of behavior we observe is to write out a stress energy tensor in a generalized coordinate space. The result is a description of gravity without any "spooky action at a distance" - in fact, the solution to the general relativistic equations that describe a planetary system yield accurate predictions about orbits; and do not rely on any weird spurious "force" of gravity. Gravitation is instead a property of the system - it is a description of the way the masses influence each other. Nimur (talk) 04:12, 30 July 2010 (UTC)[reply]
Piper nigrum and alcohol
So I was making steak au poivre the other day, and once the steaks were seared and removed from the pan, the recipe called for cognac to be added to the still-hot pan and the vapors ignited. Quite the impressive show resulted---the flames themselves were only about a foot tall, but the plume of hot air was at least six feet tall. I don't really want to recreate that indoors, but I don't really want to have to find an outside area free of flammables before I can make the dish. I'm wondering if I can skip the flashy vapor-igniting and just cook the alcohol off, though I'm concerned that without that step that some of the harshness of the cognac will remain. I certainly don't want to skip the alcohol both for its deglazing and solvent usefulness. Thanks for the help!72.219.136.28 (talk) 06:37, 30 July 2010 (UTC)[reply]
You should be okay to simply cook out the alcohol, if you make some changes. Igniting the flames like that serves two purposes: first, it is theatre (i.e. simply a show); second, it serves to remove the alcohol quickly. Depending on what else you plan on adding to the dish, you may want to significantly reduce the temperature to avoid burning something during the longer cook time. Incidentally, the alcohol never cooks "out" completely. Well, never is a long time, but you catch my point; don't try to just cook out (or flambé out!) alcohol for someone who is intolerant or something. Matt Deres (talk) 13:58, 30 July 2010 (UTC)[reply]
My wife (who is French and therefore "correct-by-definition" about all culinary matters) says that you're probably using WAY too much cognac. To cook a couple of steaks "au-poivre", she'd first cook the steaks in cracked soft/green peppercorns with a simdgeon of butter and ground black pepper until they are essentially "done". Then she'd use just one tablespoon of cognac for two steaks - it's a strong flavor and you don't want to overpower the cream and make it bitter. The flames are generally rather unimpressive, particularly because alcohol flames are almost invisible. It's hard to get the cognac to ignite in the pan - so she lights it in the spoon and gently pours it onto the steaks while it's still burning. Don't pour straight from the bottle into the pan! She douses the pale blue flames very quickly by pouring on the cream - then turns off the heat and allows maybe 10 more seconds in the pan to get the cream hot and mixed in with the cognac, pepper and meat juices - and then serves it straight to the table. But you do need to burn off the alcohol - it has to be added towards the end so that the flavors in the cognac don't get destroyed by the cooking - and you don't want to overcook everything else while you wait for the alcohol to simply evaporate off. If you are getting a gigantic and colorful fire - then you may have set the fat from the steaks on fire - and that's "A Very Bad Thing" for both safety and flavor. Since you're going to be serving the sauce from the pan - and you don't want a lot of ikky beef fat in it - if there is a lot of fat in the pan - then remove most of it before adding the cognac. She suggests not cooking more than a couple of steaks in a pan - if you need to cook more then two or three steaks then use a second pan so that you can control everything more closely in that busy half minute at the end of cooking. Also, avoid leaving the steaks too rare with this recipe because the blood in the cream doesn't look appetizing - so limit yourself to medium-rare. The plates you serve onto need to be really hot. She uses a sprig of parsley to decorate (and, I suspect, to meet the "7 ingredients rule" of French cooking that I've deduced from watching her cook!) Because the timing of all of this is so important, she tends to serve vegetables that can stand being a little over-cooked - asparagus is generally her choice - because then she can give full attention to the steaks without having to panic about not over-doing the veg. SteveBaker (talk) 14:32, 30 July 2010 (UTC)[reply]
Quantum Mechanics Problem
I'm working through a quantum mechanics book and have encountered a problem with one of the exercises and I need a little help. The problem defines a phase flipping operator in d dimensions to be a unitary operator with eigen values +1 or -1. Then, it wants me to show what happens if we take the whole collection of such operators relative a specific shared basis of eigen vectors and average their effect on a a density operator. However, by linearity, this should be the same as applying the average of the unitary operators to the density operator, but since there will be as many +1's as -1's for any eigen |k>; the overall operator appears to average to 0. This does not seem to be the answer the book wants since it says that it should preserve the populations of the density operator, but wipe out its coherencies. Thus, I suspect I am missing something really simple or the book is wrong, can anybody point me to which one of these is the case; if the former, can I have a small hint as to what I am missing. Thank you:) 66.202.66.78 (talk) 09:29, 30 July 2010 (UTC)[reply]
Nevermind, being half asleep, it somehow seemed reasonable to average the unitary's, get 0, then apply them; obiviously that does not follow from linearity. Instead, I should obtain that only the diagonal of the density matrix remains:) 66.202.66.78 (talk) 09:39, 30 July 2010 (UTC)[reply]
practical consequences of existence
philosophically, existance in an open question. what are the practical consequences of whether I exist? Does it really mean anything for me if in the end it is proved/discovered that I don't? —Preceding unsigned comment added by 92.224.207.77 (talk) 10:14, 30 July 2010 (UTC)[reply]
Philosophers are a waste of quarks. What is the definition of the word "exist"? Sadly, it's not a very well defined concept. Wiktionary says "to be; have existence; have being or reality". So what is "reality"? Well, again, Wiktionary comes to the rescue with:
The state of being actual or real.
The reality of the crash scene on TV dawned upon him only when he saw the victim was no actor but his friend
A real entity, event or other fact
The ultimate reality of life is it ends in death
The entirety of all that is real.
An individual observer's own subjective perception of that which is real.
If we discount circular definitions of reality as "that which is real", then we're left with only the last (and still somewhat shakey) definition - and since your own subjective perception of reality is that you exist - it is completely impossible for someone to prove to you that you don't exist. It might be possible to prove to me that you don't exist (Maybe you're an AI program designed to test reference desk response times!) - but that cannot ever (by the very definitions of the words) prove to you that you don't exist. Since it can't be proved - the question of what that might mean for you is entirely moot.
Philosophers love to argue about this circular definition of what words in English mean - but, as I said, they are a waste of quarks and we may safely ignore everything they say.
"Fears that the human race may drive itself to extinction through over-population are challenged by new United Nations figures suggesting an eventual equilibrium as people in poorer countries come to understand the need for smaller families. "
http://www.guardian.co.uk/world/2004/nov/06/population.brianwhitaker
All the Report says is that "According to the medium scenario, world population rises from 6.1 billion persons in 2000 to
a maximum of 9.2 billion persons in 2075 and declines thereafter to reach 8.3 billion in 2175. The return to replacement level fertility coupled with increasing longevity in the medium scenario produces a steadily increasing population after 2175 that reaches 9 billion by 2300. If the effects of increasing longevity are counterbalanced by fertility, population size remains constant at 8.3 billion from 2175 to 2300 as in the zero-growth scenario (figure 1)."
Does this mean that this medium scenario is the most likely?
how can you tell when a canteloupe from the garden is ready to be picked?--Horseluv10 13:02, 30 July 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs)
To summarise that video (since Horseluv has previously implied they are confined to a Whitelist that only allows Wikipedia).
The cantaloupe will get paler until it isn't green anymore, but rather a more buff-like colour. This will presumably vary between varieties.
The cantaloupe will start to smell of melon.
The melon will start to separate from the stem, so they no longer look like the stem and melon are all one piece.
You will be able to separate the cantaloupe from the stem with very gentle pulling/pushing. If you have to pull properly, or cut the melon off the stem, it isn't ripe.
Atomic theory tells us that valence electrons in an atom are the particles that are mostly involved in many phyisical or chemical activities of substances. In lasers, electrons move from one energy level to another and thereby releasing coherent and monochromatic photons. During chemical reactions,valence electrons move from one atom to another and thereby changing the properties of the substances involved.Duruing charging,substances lose or gain electrons.DOES AN ELECTRON MOVE AWAY FROM ITS MOTHER ATOM WITHOUT ITS MOTHER ATOM COMING TO CONTACT WITH AN ATOM THAT THE ELECTRON IS INTENDING TO GO TO.JUST AN ELECTRON(ALONE) MOVING AWAY FROM ITS MOTHERATOM,POSSIBLY IN A VACUUM. —Preceding unsigned comment added by Mlondo (talk • contribs) 14:37, 30 July 2010 (UTC)[reply]
The OP was asking whether there is an instance that an electron moves away from the mother atom without an ionic bond occurring. I responded by saying that I think in a plasma the electrons are stripped from the mother atom and sort of float around it. --Chemicalinterest (talk) 15:18, 30 July 2010 (UTC)[reply]
water
Ages ago I saw someone with a glass of water and a weird device with two metal prongs which they put into the water. Then the water started to go grey. I asked them what the fuck they were doing and they said it was putting silver into the water and then they'd drink it for health benefits. What the [bleep] were they doing?
What makes you think it was anything other than putting silver into their drinking water? While unconventional, this is not really that weird considering the other weird stuff people consume in the name of health. I would suspect the 'device' was some sort of soluble rod that allowed for easy introduction of silver into the water. --144.191.148.3 (talk) 15:05, 30 July 2010 (UTC)[reply]
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