Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• 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.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

May 29

On the beach

• 
• 

I'm hoping someone with some knowledge of biology has a better idea than I do as to just what I've photographed here. - Jmabel | Talk 04:24, 29 May 2023 (UTC)

Someone with better knowledge of the area's geography might not have to read the description of the images, which I repeat here, adding links: "Sandy floor of Dumas Bay at low tide, near but not within Dumas Bay Sanctuary, Federal Way, Washington, U.S." So the bay is an arm of Puget Sound. --142.112.220.184 (talk) 04:55, 29 May 2023 (UTC)

Possibly they are closed up sea anemones, though they are more common on rocks. When submerged tentacles would come out. Graeme Bartlett (talk) 07:09, 29 May 2023 (UTC)

I hadn't thought of anemones. Plausible. Any other ideas? - Jmabel | Talk 02:40, 30 May 2023 (UTC)

Given the location (Puget Sound), my thought would be geoducks. Did you dig down a bit to see what was in there? Lots of burrowing animals will also leave similar hole patterns. --Jayron32 14:29, 30 May 2023 (UTC)

You're looking at a group of Aggregating Anemones (Anthopleura elegantissima) which are closed as they are exposed to air. Underwater they'll open and expose their tentactles a Graeme Bartlett mentioned 66.194.72.18 (talk) 17:35, 31 May 2023 (UTC)

Compare with this photo: Young sea anemones - Anthopleura elegantissima - Wikimedia Commons 66.194.72.18 (talk) 17:37, 31 May 2023 (UTC)

May 30

Blackbody energy density

In blackbody radiation, how do you go from measuring radiation power per unit area to obtain energy density per unit volume? I am looking for this formula and one of the first publications that uses it, by Wilhelm Wien for example ? Because in the laws of Kirchhoff and Stephan-Boltzmann it is always a question of radiation power.

~~~~ Malypaet (talk) 07:36, 30 May 2023 (UTC)

You can imagine the radiation crossing a surface at the speed of light into a new volume. In one second it will have traveled c meters. So to get what is in one cubic meter, divide that energy by c to get energy per unit volume. ${\frac {2\pi ^{5}}{15}}{\frac {k^{4}}{c^{3}h^{3}}}$ However only half the energy is heading in the correct direction (half is going backwards) and also half is coming at different angles other than perpendicular, so you have to multiply by cos of the angle of incidence and integrate over possible angles. so then you have to multiply the answer by 4. (Another way is to consider the area of a sphere versus the area of the circle 4 πr² versus πr². Graeme Bartlett (talk) 10:04, 30 May 2023 (UTC)

So when you write the word energy, as you multiple power by one second, you use the system unit W-s, right ?

~~~~ Malypaet (talk) 11:52, 30 May 2023 (UTC)

Sure, but a joule is identical to a watt-second. --Jayron32 14:26, 30 May 2023 (UTC)

Where can I find a reference for this formula? Malypaet (talk) 21:07, 30 May 2023 (UTC)

see Stefan–Boltzmann law#Energy density for our article. Graeme Bartlett (talk) 01:28, 31 May 2023 (UTC)

The problem with Wikipedia articles is that they present the Stephan-Boltzmann law with references from the future (Planck, Bose-Einstein...). But at least you gave me a reference on the source. I just have to translate the German! Malypaet (talk) 07:24, 31 May 2023 (UTC)

I have not tried to discover the first publications as you ask. It appears that people first worked out what was happening in a spherical cavity at a particular wavelength, whereas you are interested in the result over all wavelengths. Though your question is more general than blackbody radiation, and applies to any stuff moving at the speed of light (light, neutrinos, gravitational waves). So there may be an answer for you from before Wien. Graeme Bartlett (talk) 12:22, 31 May 2023 (UTC)

May 31

Copernicus Open Access Hub

I was exploring the Copernicus Open Access Hub and was wondering how do you get the images and data from the satellites to usable images like the one's at image of the day. I was look at the IMG folder in the Granule but the files are jp2 and when converted to jpg are very dark.

PS: Here's a tutorial on accessing the images. PalauanLibertarian^🗣️ 13:56, 31 May 2023 (UTC)

The article JPEG 2000 shows comparison of .jpg and .jp2 files for the same source image and there are no obvious brightness differences. I downloaded a Copernicus image file that arrived as a .jpg with 24 bit/pixel "True color" depth and little or no compression, resulting in a large and relatively slow loading file. The free image editor IrfanView is useful for converting between .jp2 and .jpg. It can display a histogram of pixel intensities and it offers a range of brightness, contrast, tint, and gamma modifications. Philvoids (talk) 21:38, 31 May 2023 (UTC)

@Philvoids How did you download a .jpg. I thought all the img's were jp2's. I tried downloading some of them and converting them to jpgs but they are just black and white. Example1 Example2. PalauanLibertarian^🗣️ 01:19, 1 June 2023 (UTC)

Wow those converted images are a mess! My one test was to use the Download image button beside a featured .jpg (not .jp2) image on the Copernicus website. I suggest you check that you have an image editor that can properly convert .jp2 <--> .jpg in both directions. Here's a wide selection. Philvoids (talk) 14:00, 1 June 2023 (UTC)

@Philvoids Wierd. I used IrfanView to convert them. Where did use find the "featured images" in the open access hub. I know they have color images on copernicus.eu but I am looking at the Open Access Hub. PalauanLibertarian^🗣️ 15:34, 1 June 2023 (UTC)

I confess that I merely "leafed through" the Open Access Hub to see any image that I could download without registering. The image happened to be of Brac Croatia and not very helpful to you since it is an unproblematic .jpg. Sorry! Philvoids (talk) 16:11, 1 June 2023 (UTC)

Ok, it's fine. I found out you need like GIS software and you use certain color bands to create the image. Here's the brac image I believe you were looking at. PalauanLibertarian^🗣️ 21:29, 1 June 2023 (UTC)

Yes that's the image. Can you explain what you found or show a correct conversion? Philvoids (talk) 23:07, 2 June 2023 (UTC)

Here's how it works. As you can see here, the Sentinel-2 has 12 spectral bands. We need the Red, Green, and Blue (RGB) ones to make a color image. By themselves, an individual band image won't look good. So you create a raster with those three images. Basically stacking them on top of one another. Then you will see the natural color. You need a GIS software to do this, like ArcGIS or QGIS. PalauanLibertarian^🗣️ 01:28, 5 June 2023 (UTC)

June 3

Coke (not the narcotic OR the drink named after it)

When was the beehive oven (in which the volatiles were simply burned or discarded, causing severe air and water pollution) replaced by the externally-heated slot oven (which allowed the separation and recovery of coal gas, coal tar, ammonia water, ammonium sulfate/diammonium phosphate, crude naphthalene, mixed pyridines, gas benzole, merchant sulfur, etc., and is currently the most typical coke-oven design)? 2601:646:9882:46E0:EF:7B3E:F67:8348 (talk) 03:13, 3 June 2023 (UTC)

Courtesy link: coke (fuel). --142.112.220.184 (talk) 05:34, 3 June 2023 (UTC)

Right, and it has quite a lot about the (older) beehive ovens (and about the air and water pollution therefrom), but hardly a word about the (newer) slot ovens with byproduct recovery -- any info on those, and in particular on when exactly (or even approximately) they came into wide use? 2601:646:9882:46E0:10AD:F0A:60F5:174 (talk) 07:08, 3 June 2023 (UTC)

"From 1916 forward, beehive production began to decline, and beginning in 1919 more coke was made in long, narrow ... refractory retorts frequently called by-product or slot ovens".^[1] Locally the switch-over may have been earlier.^[2] An OSHA Proposed Standard of 1975 states in its considerations, "Prior to 1910, the use of beehive ovens predominated in the production of coke" and "The first by-product coke ovens in the United States began operation in the 1890's."^[3]  --Lambiam 09:28, 3 June 2023 (UTC)

See Coal gasification#History. From the end of the 18thC coal gasification started, and by the mid 19thC "every small to medium-sized town and city had a gas plant to provide for street lighting" in the UK. I suspect that the answer to the OP's question is "it depends where you are talking about". Given the importance of the Boulton & Watt factory at Soho, I would guess that from 1805 onwards mill owners would be pushing for a reliable supply to enable working after dark. It is perhaps germane to point out that during the winter it gets dark by 4pm in places such as Birmingham and Manchester. Martin of Sheffield (talk) 10:32, 3 June 2023 (UTC)

In the UK;

By-product ovens only gradually superseded non-recovery ovens. The proportion of coke made in the latter declined from 93 percent in 1900 to 1.5 percent in 1938, and by 1938, only 450 beehive ovens and 80 Coppice non-recovery ovens remained in use. The last British beehive ovens at Victoria Whinfield colliery in County Durham, were shut down in 1958.

By-Product Coking Plants in Britain: an Outline History by Dr D. G. Edwards

Alansplodge (talk) 12:31, 3 June 2023 (UTC)

This suggests very similar paces in the UK and the US. Although beehive coke production was environmentally damaging, this was not a likely consideration in the individual producers' decisions to convert. The economic considerations (maximizing profit) may have led at the same times to the same outcomes on either side of the Atlantic.  --Lambiam 14:53, 3 June 2023 (UTC)

@Alansplodge: - that's a most interesting link. Edwards must be concentrating on plants used purely for coking, he mentions collieries and steelworks, rather than plants run for the town gas. for instance he states (p 69) that The start-up dates of the plants, ... range from 1882 ... which is clearly incorrect for gas production. Later on the same page he states The three built at gasworks ... and gives dates of 1912, 1931 and 1950. Compare this to Barty-King who includes as an appendix a description of the the Gas Light and Coke Company's gasworks in Horsefeyy Road, London which is dated 1830s and includes a description of the stokers pulling the coke out of the furnaces to a cellar below. Indeed, at the start of chapter 3 (p 41) Barty-King mentions the royal charter that the Gas Light & Coke Company obtained on 30 April 1812 to lay pipes in the streets of London and Westminster.

What would be very interesting would be to find out the proportion of private coke-works to that of the gas and coke companies. Edwards' 1882 date might be a little surprising for Abraham Darby who in the 1690s witnessed coke being used for malting and later famously used it to smelt pig-iron. Very odd! Martin of Sheffield (talk) 16:21, 3 June 2023 (UTC)

I read it that Edwards was writing specifically about "by-product coking plants" (aka slot-ovens?) by reference to the title of his article. However, I know almost nothing about coke production, except that I used to go skiing on an old coke-works slag heap at Beckton Alps. Alansplodge (talk) 17:06, 3 June 2023 (UTC)

References

Energy, Joule and Watts-second

A moving object or a mole of ideal gas in thermal equilibrium has a constant energy over time, for example 10 Joule. For an electric current with a power of 10 Watts (10 Joule/second) , in 1s we will count 10 Watts-second, in 2s 20 Watts-second.

We clearly see there that there is a temporal difference between Joule and Watts-second energy. Why it doesn't show up in wikipedia articles ?

How could we qualify this difference? Malypaet (talk) 22:02, 3 June 2023 (UTC)

If it's superconducting and disconnected from power it's the same electrons being double, triple counted and so on, if the circuit is to do most useful things it'll stop working by the time the joules run out. If room-temperature superconducting electromagnets are ever invented they could be be turned into a toy that only needs to be connected to power once to levitate a permanent magnet against gravity indefinitely in a place that never reaches 20 Celsius or above. Not very useful as there are already toys that levitate things with permanent magnets. Sagittarian Milky Way (talk) 22:29, 3 June 2023 (UTC)

An electric current has no power of itself. It's just a flow of charge. If there's current passing down a potential difference, for example through a resistor, energy gets converted, for example into heat, equal to the voltage times the current every unit of time. The rate at which energy gets converted is a power. In an object moving at constant speed, no energy gets converted or moved from one system to another. There just is an amount of energy. PiusImpavidus (talk) 09:28, 4 June 2023 (UTC)

If there is no resistor , there is no current. So current is linked to power, the flow of charge acting as an energy cargo. Also in space between the sun a direction with no obstacle to the infinity, you can have a flow of photon passing into a power meter indicating power, and then the energy is only converted in the instrument of measure, right ? Malypaet (talk) 10:32, 5 June 2023 (UTC)

June 4

What is a lama flower?

I was reading something that mentioned lama flowers, so I tried to look them up. Nothing on Wikipedia. A few google results (once you filter out "llama" suggest they might actually be something that exists, but I can't find any information on them. Mostly interested in where they grow and what they look like. Anyone have any information here? -- Avocado (talk) 02:28, 4 June 2023 (UTC)

Could it be Diospyros sandwicensis? Abductive (reasoning) 02:48, 4 June 2023 (UTC)

Maybe? There wasn't a lot of detail about them in the text where I read the term (it was the description of a design on a garment). Thank you for the link! -- Avocado (talk) 03:09, 4 June 2023 (UTC)

Hm, or maybe it's a heraldry thing or something and I'm asking in the wrong place? I can only half make sense of the google translation, but the French language article about a town in Corsica called Lama [4] mentions something about it in relation to flowers... -- Avocado (talk) 03:18, 4 June 2023 (UTC)

That's a national town beautification program in France: https://www.villes-et-villages-fleuris.com. Abductive (reasoning) 04:48, 4 June 2023 (UTC)

The term "Lama Flower" is used here for Chenopodium capitatum. This is a single hit, so it is not a common common name.  --Lambiam 11:22, 4 June 2023 (UTC)

Here a dress is described as being "full trimmed with splendid lama flowers". The dress in question is called a "lama dress", apparently quite a thing in 19th-century England, as the attire of another noble lady described on the same page, as well as one two pages earlier, is also called that. A search for "lama dress" confirms this. Apparently, lama flowers only grow on lama dresses; it is not a type of flower, but a design of a flower executed in some way referred to as lama, as seen in a description of the 1816 wedding dress of Princess Charlotte: "The Wedding Dress, composed of a most magnificent silver lama, on net, over a rich silver tissue slip, with a superb border of silver lama embroidery at the bottom, forming shells and bouquets; above the border a most elegant falling, tastefully designed, in festoons of rich silver lama, and finished with a very brilliant roleau [sic] of lama."^[5] After much searching I found a definition in The Century Dictionary :

lama³ (lä′mä), n. [Sp., gold or silver cloth, a particular use of lama, plate: see lame³, lamina.]
   1. A rich material made in Spain in the fifteenth century, described as a cloth of silver shaded and watered.
            A dress of silver lama, over French lilac.
                        Armitage, Old Court Customs, p. 36.
   2. A similar stuff of modern manufacture. See lama d’oro, below. Spanish Arts (S. K. Handbook ).—Lama d’oro, a silk stuff interwoven with threads or flat strips of gold, especially of a kind made in Italy.

The 19th-century sense would have been the "similar stuff of modern manufacture", but apparently not only lama d'oro but also lama de plata.  --Lambiam 12:33, 4 June 2023 (UTC)

Aha! Mystery solved. Thank you, @Lambiam! Now to see if there's any source that will describe what they actually looked like -- but I suspect this is not the venue for that. -- Avocado (talk) 13:40, 4 June 2023 (UTC)

Isn't this just Lamé (fabric)? Here are some lamé flowers. (I use the acute accent advisedly.)  Card Zero  (talk) 16:46, 4 June 2023 (UTC)

Yeah, I'm familiar with lamé. "Lama" looked like it could have a different meaning; and my understanding had been that lamé didn't exist in the period in question (possibly due to a misreading of our cloth of gold article? The distinction between the two isn't entirely clear to me; or perhaps lamé is a subset of cloth of gold? What distinguishes it from other types?). -- Avocado (talk) 16:51, 4 June 2023 (UTC)

Delta ray effects

What would the effects of loose delta rays interacting with matter be? For example, would delta rays going through organic matter cause damage like other radiation? Edward-Woodrow :) _[talk] 17:45, 4 June 2023 (UTC)

It is basically a name for Beta rays produced as a side effect off other radiation, so that article should say what you want. NadVolum (talk) 18:45, 4 June 2023 (UTC)

The energy of a delta electron (or "secondary electron") is typically much lower than that of an electron emitted by beta decay, but still enough to potentially cause damage; see Ionizing radiation § Beta particles.  --Lambiam 23:55, 4 June 2023 (UTC)

Climate questions

1. Are there any places in North America with Dfd, Dwd or Dsd climates? Why does North America have less severe winters than places at similar latitude in Siberia?
2. Are there any places in Europe with Cw or Dw climates?
3. Are there any places in South America where average low temperature if coldest month is under -10° C?
4. Which is coldest city in Poland?

--40bus (talk) 20:00, 4 June 2023 (UTC)

Presumably your alphabet soup is referring to coding in Köppen climate classification. I note that much of Alaska is in the same zone and code designation as much of Siberia is. The lower 48 have the relatively warming factor of the Pacific to the west, which Siberia does not. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:55, 4 June 2023 (UTC)

1) Yes, some parts of Alaska, the Yukon and the Northwest Territories have these climates (mainly at higher elevations and not too far from the coast).

2) No, because the high humidity coming in from the Atlantic at all seasons pretty much precludes a dry season of any kind.

3) Only at high altitudes in the Andes, if at all -- because most of South America outside the tropics is near the sea, winter temperatures (outside the high Andes) never go down very low.

4) From the partial info I found so far, that would be a tie between Danzig and Belostok, both of which have an annual mean temperature of 7.7 C.

2601:646:9882:46E0:989D:AD1C:1D66:1004 (talk) 03:59, 5 June 2023 (UTC)

Large parts of Europe have a dry season, but that's summer: Mediterranean climate.

Zakopane, a ski resort in the Tatra mountains, must be one of the coldest cities in Poland. Yearly average 6.2°C, climate type Dfb. PiusImpavidus (talk) 08:42, 5 June 2023 (UTC)

June 5

Do vaccines have any efficacy once someone is in the throws of a viral sickness?

I am no doctor or scientist, but I thought I had a pretty strong understanding of how vaccines work.

(Spoiler alert for a popular show).

I was just watching the series Utopia (the American 2020 remake; not the 2013 British version). At a plot point, they have a character who is supposedly a virologist (no less), who has come prepared with a vaccine for a specific flu. Another character is in the throes of the virus, and this virologist is begged by the father of the sick character to save his daughter by testing the vaccine on her (as if a vaccine is some type of a magic bullet antiviral). My understanding is that this would have no effect whatsoever; that this is obvious and basic if you know how vaccines work; that this is the heart-rending misunderstanding I read about of some people in hospitals during the pandemic— dying from the infection who had refused the vaccine, who now finally wanted it, and had to be told “it’s too late”; “that’s not how vaccines work”, and yet I am utterly baffled. How could they have a show that has virology and viruses and vaccines at its very heart and not understand this basic stuff and perpetuate this misunderstanding—especially now. But then I thought am I wrong in some way about this? 108.41.147.194 (talk) 04:54, 5 June 2023 (UTC)

Haven't seen it, but TV can be pretty bad when it comes to medical stuff and plain not doing the research, or not caring about errors as long as it makes good drama. How many times have you seen a medical drama (who you'd think would likely have doctors working as technical consultants) where the patient's heart stops and the doctor is like "defibrillator now!", or a pneumothorax is treated by stabbing the patient, ice-pick style in the chest with a syringe, followed by a loud hiss of air and then the person waking up and being pretty much fine straight after? I used to watch House and I remember a website back in the day that was dedicated to pointing out all the medical inaccuracies/straight up nonsense in the show. There was a lot. Iloveparrots (talk) 06:05, 5 June 2023 (UTC)

You are not wrong. A vaccine works by coaxing the immune system to produce antibodies against a potential pathogen, so it can be nipped in the bud on infection by the primed immune system. Administering it to an infected patient whose immune system is already in a total state of war makes no sense; it is like installing a fire alarm system in a building that is on fire.  --Lambiam 09:57, 5 June 2023 (UTC)

Injecting a vaccine is not always too late even after someone has caught an infection. The most well-known example for this is the rabies vaccine. Although the vaccine is routinely given to pet dogs, it is not deployed at large scale to humans, probably because it has too severe side effects. However, when a human gets bitten by a wild animal or an unvaccinated dog (in areas where rabies is endemic), it is suspected that they may have got rabies, so doctors give them the rabies vaccine as a precaution. The vaccine still works even when the wild variant of the virus is in the human. – b_jonas 14:33, 5 June 2023 (UTC)

Any symbol for heights below sea level?

The article Height above mean sea level mentions several variants for heights above sea, like AMSL, MAMSL, MSL, MASL for '(meters) (above) (medium mean) sea level.' The existing variety suggests none of them is commonly accepted. Anyway, it clearly documents the fact some commonly understood acronyms exist.

On the other hand, however, the term Below sea level redirects to List of places on land with elevations below sea level, which does not use any symbol for the notion and just gives negative heights everywhere. The article on the Dead Sea uses a negative number for 'Surface elevation' in the infobox and positive numbers with a plain text explanation 'below sea level' troughout the text. The only exception is the 'Max. depth' in the infobox, where BSL is used to distinguish the depth relative to the whole-world's sea level from the depth within the Dead Sea itself.

There is a BSL dab page in Wikipedia, but this doesn't mention 'below sea level' at all.

So, here my question comes: is there any abbreviation or other symbol used in English written texts to denote heights in depresions? --CiaPan (talk) 09:32, 5 June 2023 (UTC)

See Sea_level#Height above mean sea level last paragraph: "In the rare case that a location is below sea level, the elevation AMSL is negative", so probably not. Martin of Sheffield (talk) 09:43, 5 June 2023 (UTC)

The abbreviation "BMSL" is used in our article on the Sotra Bridge. There are sporadic other uses of this abbreviation.^[6][7][8]  --Lambiam 10:07, 5 June 2023 (UTC)

Cosmological Redshift

True or false - this breaks the Law of the Conservation of Energy? A photon losing freq is a photon losing energy so where does it go?

What does Relativity (no aether) have to say about this?

An aether explains this easily - it is the aether doing the expanding. Byron Forbes (talk) 12:12, 5 June 2023 (UTC)

The photons are being measured in a different reference frame to where they started, you might as well ask why a a car going the same way on the road has lost so much energy and one going in the opposite direction has gained so much. If two cars have a crash it'll show they really have lost or gained energy relative to each other. NadVolum (talk) 13:12, 5 June 2023 (UTC)