Science desk
< July 21	<< Jun \| July \| Aug >>	July 23 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

July 22

Buzzing flies

Why is it that a house fly will buzz loudly sometimes when it is flying about, and at other times, fly silently. This can change from one to the other in the course of half an hour. Bielle (talk) 02:18, 22 July 2011 (UTC)[reply]

I can't find anything about this to cite, but I'm pretty sure it's your ears that are the problem. A house fly does not change it's "buzz". But, you know, it's such a high pitched sound, it's not surprising you only hear it when it is a certain relative distance from your ears. Quinn ^{❀ BEAUTIFUL DAY} 04:47, 22 July 2011 (UTC)[reply]

Sometimes, flying past my ear, it buzzes (and the buzz is not "high pitched"); sometimes it flies past silently. This buzz is so loud when it happens, I can hear it across the room. Bielle (talk) 04:52, 22 July 2011 (UTC)[reply]

Are you sure it's the same fly everytime? Plasmic Physics (talk) 05:42, 22 July 2011 (UTC)[reply]

Some species of fly buzz loudly and fly erratically when they think they are in danger (e.g. when I approach with a fly swatter). Presumably that's some sort of defence mechanism. Are they trying to sound like a wasp or bee? Dbfirs 07:40, 22 July 2011 (UTC)[reply]

I notice that Calliphoridae such as bluebottles seem to make more noise than Muscidae such as house flies, which can sometimes be virtually silent, until sprayed with insecticide anyway.--Shantavira|^{feed me} 07:43, 22 July 2011 (UTC)[reply]

@PLasmic Physics: Yes, I am reasonably sure it is the same fly. It was banging in and out of a lampshade beside my bed, and then buzzing (or not) off again into the room. It's not a bluebottle, Shantara. Bielle (talk) 15:43, 22 July 2011 (UTC)[reply]

If you're sure it's the same fly, then note that fly wings can follow many different stroke patterns, depending on the maneuver. Each of these patterns can potentially have a distinct audio signature. Our article insect flight points out "the phenomena associated with flapping wings are not completely understood or agreed upon." Anecdotally, (fixing range and individual), I think a housefly sounds louder when ascending, and in the half-second prior to landing. SemanticMantis (talk) 17:54, 22 July 2011 (UTC)[reply]

And, specifically, wing motions which create turbulence in the air will tend to make more noise than those which allow for laminar air flow. StuRat (talk) 04:30, 23 July 2011 (UTC)[reply]

Succulent plant in the UK

Found this plant growing on concrete (on a layer ~1cm of moss). It is easily identifiable ? : I'm assuming it's not native (I think I've seen plants like this in garden centres for indoors..) It seemed to be doing quite well - Are these plants known as an successful alien species in the UK. (I'm suprised it survives a winter) Imgaril (talk) 03:18, 22 July 2011 (UTC)[reply]

If it is the same thing I grow here in the southern U.S. (and it looks like it) we call it a "primitive plant" (I'm sure there is a more formal name, but I only know it as that). I'm hardly an expert, but I can tell you it's a succulent, and that it is very hardy. In fact, if you "pinch off" one of the "leaves" and stick it in some soil, it'll grown a new plant. I'll leave the specifics to any experts that want to comment. Cheers! Quinn ^{❀ BEAUTIFUL DAY} 04:42, 22 July 2011 (UTC)[reply]

Looks like some sort of stonecrop. There are many species, some native to Europe. Looie496 (talk) 06:10, 22 July 2011 (UTC)[reply]

This is White Stonecrop Sedum album. A curious little plant, but pretty common in gardens, and as pot plants in the UK. It thrives on dry poor soils, walls or where nothing else will grow - hence your find on concrete. It will certainly survive frost! Richard Avery (talk) 06:49, 22 July 2011 (UTC)[reply]

Thank you very much. Stonecrop is a very fitting name.

Resolved

Sandwich ideas?

I want a sandwich that is not soggy, holds well without refrigeration, and is healthy to eat. Is that to much to ask? I don't like deli meat. Peanut butter isn't good in the long run. Sugar-free jelly tastes weird, and fruit jelly is fructose. Imagine Reason (talk) 10:24, 22 July 2011 (UTC)[reply]

As someone from the land down under, I must recommend a Vegemite sandwich. HiLo48 (talk) 11:43, 22 July 2011 (UTC)[reply]

Quote I heard on the radio once: "Vegemite is Marmite for girls!" Alansplodge (talk) 21:43, 22 July 2011 (UTC)[reply]

Obviously just a jealous Pommie announcer. HiLo48 (talk) 04:10, 23 July 2011 (UTC)[reply]

What's wrong with fructose? Dauto (talk) 12:12, 22 July 2011 (UTC)[reply]

Try an Avocado sandwich! - Lettuce, avocado, onions, 1 tomato slice, some swiss cheese a bit of mustard. Dauto (talk) 12:17, 22 July 2011 (UTC)[reply]

Amused that this is posted in the science section, I googled /sandwich science/ and found this nice piece from Robert Krulwich, who covers the science of sandwiches from a few angles [1]. SemanticMantis (talk) 12:53, 22 July 2011 (UTC)[reply]

"Not soggy" comes down to using the correct bread. Avoid the heavily processed "Wonder bread"-type bread, and instead go for something more hardy, if I know I am going to use it quickly I always get something fresh baked and have the store slice it fresh for me. --Jayron32 12:54, 22 July 2011 (UTC)[reply]

Avocado and tomato won't work, neither holds well without refrigeration. There is some oxygen-sensitive chemicals present. When these chemicals are exposed to oxygen, they change into new ones that negatively impacts the taste. If an avocado sandwich is not consumed soon after the avocado is cut, it will taste like someone played a prank on you, by adding moisturising cream to your sandwhich^{[citation needed]}. Descriptions may vary, generally that is the taste I perceive. Plasmic Physics (talk) 13:01, 22 July 2011 (UTC)[reply]

Over time, condiments like mustard tends to soak into the bread, unless you use margirine, butter or equivalent. Plasmic Physics (talk) 13:04, 22 July 2011 (UTC)[reply]

Rye or wholegrain is a good choice for a healthy bread that keeps well, without going soggy too soon. Plasmic Physics (talk) 13:06, 22 July 2011 (UTC)[reply]

Cheese won't make the bread soggy, and will keep till lunchtime without refrigeration (in fact, cheese tastes better at toom temperature than at fridge temperature). DuncanHill (talk) 13:33, 22 July 2011 (UTC)[reply]

Cheese at "tomb temperature" ? Do you store it in the family crypt ? :-) StuRat (talk) 14:05, 23 July 2011 (UTC) [reply]

I don't have time to search for actual products you can buy today, but I've heard of a variety of edible films that are intended to solve the sogginess problem. Some are constructed from chitosan, others from zein (being researched by US military for MREs). See e.g. this Science Daily blurb: [2]. The idea is to construct the sandwich as /bread-edible film-condiment-payload-condiment-film-bread/ to reduce moisture spreading to the bread, while retaining freshness. SemanticMantis (talk) 14:14, 22 July 2011 (UTC)[reply]

Why would you need some high-tech film? A decent smear of butter waterproofs the bread just fine, in my experience. Well enough that the cucumber from a cheddar and cucumber sandwich doesn't soggify the bread before lunchtime when the sandwich is stuffed in a backpack for the morning, at least in UK weather. Lemon juice on or mashed into the avocado helps, by the way, in my experience. 86.164.57.187 (talk) 14:21, 22 July 2011 (UTC)[reply]

I don't think we need these, I just wanted to add more science-y stuff to this thread ;) SemanticMantis (talk) 17:37, 22 July 2011 (UTC)[reply]

I've just been converted to spreading hummus on bread instead of butter or margarine - less fat and better for you. And actually quite tasty! You may not find it does what you want though. You can get different cooked meats too, not just ham. Have you tried, for example, tongue or corned beef? Another thing to try is to change the bread. A friend of mine uses tortilla wraps to make her sandwiches and they seem to keep just fine. --TammyMoet (talk) 14:56, 22 July 2011 (UTC)[reply]

Spinach-and-cheese sandwich. Pile on other dry veggies like sprouts, onions(yuck), or lettuce for a broader range of flavors. i kan reed (talk) 16:30, 22 July 2011 (UTC)[reply]

Keep the bread and moist ingredients in separate baggies until serving. Problem solved. μηδείς (talk) 17:39, 22 July 2011 (UTC)[reply]

Agreed. If you're not willing to do this, though, I must echo the earlier cheese suggestion to keep the wet ingredient from making the bread soggy, and slices of American "cheese" work best. Breaded meat patties also work well. So, maybe you could have bread, then a slice of "cheese", then some mustard (avoid mayo since it spoils too quickly), then a breaded meat patty. StuRat (talk) 04:06, 23 July 2011 (UTC)[reply]

You know, real cheese actually comes in slices too. I have on my desk a packages of slices of Black Diamond extra-sharp cheddar, aged one year, very tasty. It should work almost as well as that borderline-edible soft rubber product that I refuse to sully my country's name by referring to as American cheese. --Trovatore (talk) 04:28, 23 July 2011 (UTC)[reply]

Yes, real cheese comes in slices, but, unfortunately, bacteria, just like humans, consider that to actually be edible. StuRat (talk) 12:17, 23 July 2011 (UTC)[reply]

In Britain we have devices known as knives which enable us to make slices for ourselves. DuncanHill (talk) 12:22, 23 July 2011 (UTC)[reply]

It's difficult to slice cheese that thin using a knife without creating gaps (especially with hard cheeses), thus allowing bread to get soggy. There are devices specifically designed for slicing, but then there's all the bother in trying to clean them. I find it much easier to buy it pre-sliced. StuRat (talk) 13:58, 23 July 2011 (UTC)[reply]

I think most of you are missing a crucial point, the sandwich must be healthy to eat. Plasmic Physics (talk) 13:40, 23 July 2011 (UTC)[reply]

The goals of "healthy" and "lasts forever without refrigeration" are diametrically opposed, in most cases. Bread that never spoils isn't very healthy, for example. There are some food items that might meet both qualifications, like honey, but you can't make a sandwich out of those alone. StuRat (talk) 14:01, 23 July 2011 (UTC)[reply]

So, the question is practically unanswerable, except if he/she is willing to sacrifice one of the prerequisits? Plasmic Physics (talk) 15:12, 24 July 2011 (UTC)[reply]

Theoretical Physics - Extreme Edition (Now with black holes)

Simple question with (I'm sure) a very complicated answer: If we could magically just "turn off" gravity, what would happen to a black hole? Specifically, what would it look like? Goodbye Galaxy (talk) 13:42, 22 July 2011 (UTC)[reply]

Exploding stuff. Maybe just dissipating stuff. Probably stuff that has lost all sense of form or order. But without the attractive force of gravity holding all that stuff together, it probably won't hold together. Also, it bears noting that whenever a question verges from scientific plausibility into the realm of magic, a perfectly correct answer is always: "It's your magic. What would you like the correct answer to be?" — Lomn 13:56, 22 July 2011 (UTC)[reply]

Thought experiments are totally valid, and often require a bit of magical setup. And this question just has a magical "trigger". The actual process should be entirely physics-based. Goodbye Galaxy (talk) 14:13, 22 July 2011 (UTC)[reply]

Let's please not conflate well-regarded and famous thought experiments, where the "magical setup" bit is to route around impracticality, with "let's magically alter the fundamental nature of the universe". — Lomn 14:26, 22 July 2011 (UTC)[reply]

Since we have (basically) no direct observational data on black holes, all that we can surmise about them comes from theoretical equations. I'm wondering what would happen in these equations when the strength of gravity is set to zero. It seems to be the same type of thought experiment as a weakless universe. Next time I'll avoid the use of the word "magic" to circumvent conversations like these. Goodbye Galaxy (talk) 14:41, 22 July 2011 (UTC)[reply]

The weakless universe is one which has never had any weak interaction to begin with. If you imagine a universe without gravity, the answer is simple: there would not be any black holes. As to "turning off" gravity at some point in time everywhere, that leads to severe problems with the notion of instantaneity, in particular in black holes where space-time is so messed up. --Wrongfilter (talk) 16:08, 22 July 2011 (UTC)[reply]

You guys are being no fun. The exact behavior of black holes is not perfectly understood. For a similar concept, if you took a "brick" of netronium and "magically" removed gravity, the weak force would prevail of the strong(and there would be no electromagnetic), and you'd see a LOT of beta decay really quickly. My guess is the resulting mechanical energy released would be on the scale somewhere between fission-weapons and matter-antimatter interaction. Big big boom, depending on your mass. i kan reed (talk) 16:28, 22 July 2011 (UTC)[reply]

one of the black hole is the big bang (universe) becase it cercle in time its revers its gravity in time . Thanks — Preceding unsigned comment added by 84.229.134.89 (talk) 18:11, 22 July 2011 (UTC)[reply]

With no gravity you're left, abruptly, with a naked singularity. I don't know what forces would hold such a thing together or push it apart - normally it is thought to go away as a hole decays because you're essentially dumping "negative mass" into it in the form of half of a pair of virtual particles that arose spontaneously. If gravity were turned down over time I suppose you'd have some kind of Hawking radiation from the shrinking horizon that is much like the final decay of the hole, but you'd need some kind of physics to describe the changing gravity. Wnt (talk) 18:31, 22 July 2011 (UTC)[reply]

The black hole stays black for a while because everything that has already gone through the Event horizon is gone for good. Matter continues moving towards the EH as it obeys Newton's first law and nothing remarkable happens when it enters the place where the black hole used to be. Cuddlyable3 (talk) 18:34, 22 July 2011 (UTC)[reply]

"Gone for good" is only the case if you take various sci-fi stories seriously. We have no evidence that the event horizon is a magical gateway to nowhere--it is just the threshold where the escape velocity--due to gravity--reaches the speed of light. Simplest assumption is that you'd get a whopping pseudo-supernova consisting largely of gamma rays, per Wnt's Hawking radiation allusion. μηδείς (talk) 18:44, 22 July 2011 (UTC)[reply]

The question makes no sense. No meaningful answer can be given. Dauto (talk) 19:37, 22 July 2011 (UTC)[reply]

I second Dauto. The question asks us to assume that we can ignore a fundamental property of the universe, and does not even formally specify how we should proceed to make that assumption. There is no way we can meaningfully apply formal physics to answer such a question. Nimur (talk) 20:36, 22 July 2011 (UTC)[reply]

No, the question simply asks us how the gravity versus repulsion equation governing the collapse of a massive object is balanced once the gravity term is removed from the equation. μηδείς (talk) 22:44, 22 July 2011 (UTC)[reply]

The question is specific about black holes which don't work the way you describe. What happens when gravity is turned off? should we replaced the warped space with some flat space? probabily yes, since gravity IS the warping of space. But a black hole is just an specific form of space warping, if you remove the warping, you remove the hole and the question makes no sense. The best you can do is simply assume that the hole is replaced with a naked singularity in a flat space-time. What happens to the singularity? is it stable or unstable? There is no physical principle to help you answering that question which makes it un-answerable. Dauto (talk) 23:24, 22 July 2011 (UTC)[reply]

Or, to rephrase that: gravity is not an "on/off" switch. It's a fundamental property that describes the behavior of the universe. You can't "turn it off." You could develop a hypothetical formal system that explains a different, hypothetical fundamental behavior of the universe. But, to make such a formal system that is self-consistent, and agrees with observation about the universe, you would need to use a more rigorous explanation than "gravity is off."

If we restricted discussion to Newtonian physics, we could say "Well, what if the Gc gravitation constant equaled zero?" That's a little bit of a formality, but it seems conceptually similar to what the OP intended when they said "turn off Gravity." And then we could solve equations of Newtonian motion for that scenario. The results would be unrealistic, because the hypothetical situation is not a description of the real, physical universe; but at least they would proceed according to a formal physical description.

But we can't use Newtonian physics to describe black hole physics. So, you'll have to come up with a different formalism to express "turning off gravity," and do so in the context of a mathematical and physical framework that permits black holes. In the absence of that formal explanation, we can't proceed with any analysis.

This is a classic case of "I want to philosophize and ruminate about black holes, but I don't feel like spending several years to learn the formal description of a black hole (that sounds too difficult); so I'll just pretend that mathematical formality doesn't matter in physics, and pretend I can make random assumptions about black hole behavior." Nimur (talk) 00:22, 23 July 2011 (UTC)[reply]

agin in Newtonian physics , in ordenry gravity when its gets infinity small the gravity get infinity and flip in time ,the opesit derction , thanks agine

As the article says, the Higgs field has a "non-zero expectation value" in vacuum, which gives mass to other particles. Question: is there any way that the strength of the Higgs field could vary in a region of space? Would this change the mass present - even the mass of a black hole? For instance, say, if you could somehow collect Higgs particles from a particle accelerator and bottle them up in a small area? Wnt (talk) 22:10, 23 July 2011 (UTC)[reply]

I don't know much about particle physics, but even massless particles cause gravity proportional to their energy, so I don't think the Higgs field really makes a difference here. Rckrone (talk) 01:33, 24 July 2011 (UTC)[reply]

please help me understand a paragraph in Masters and Johnson

Assigned male homosexual study subjects A, B, and C..., interacting in the laboratory with previously unknown male partners, did discuss procedural matters with these partners, but quite briefly. Usually, the discussion consisted of just a question or a suggestion, but often it was limited to nonverbal communicative expressions such as eye contact or hand movement, any of which usually proved sufficient to establish the protocol of partner interaction. No coaching or suggestions were made by the research team.

—p. 55

According to Masters and Johnson, this pattern differed in the lesbian couples:

While initial stimulative activity tended to be on a mutual basis, in short order control of the specific sexual experience usually was assumed by one partner. The assumption of control was established without verbal communication and frequently with no obvious nonverbal direction, although on one occasion discussion as to procedural strategy continued even as the couple was interacting physically.

—p. 55

I can't understand the meaning, I humbly believe it should be simplified. — Preceding unsigned comment added by 109.64.39.228 (talk) 18:29, 22 July 2011 (UTC)[reply]

Clearly this is one of those cases where a video is worth a thousand words. It wouldn't hurt to ask if they'd release this material to Wikimedia Commons for, um, academic study and research. ;) Wnt (talk) 18:34, 22 July 2011 (UTC)[reply]

Simplification: Gay men know what they want and just go to it. Gay women have to have a talk first to work out their Pecking order. Cuddlyable3 (talk) 18:40, 22 July 2011 (UTC)[reply]

That's not how I'd interpret it - the researchers sound a bit intrigued just how the women do decide which one is "on top", so to speak, but according to them it wasn't by talking. Wnt (talk) 22:01, 22 July 2011 (UTC)[reply]

It says that homosexual men manage to figure out who is doing what with a few verbal and a lot of nonverbal communication. Homosexual women manage to work that out without saying anything and without any obvious nonverbal communication. (So it is really the exact opposite of C3's reading.) --Mr.98 (talk) 22:13, 22 July 2011 (UTC)[reply]

Agreed. C3 must have accidentally read it backwards. APL (talk) 10:20, 23 July 2011 (UTC)[reply]

Those are quotations from their book. We can't alter quotations. If you think an explanation is needed, that's reasonable, and it would be reasonable to say so on the talk page of the article. Looie496 (talk) 19:00, 22 July 2011 (UTC)[reply]

I think the OP is saying that rather than quotations, a summary or distillation should at least be included (if not the sum total of what is there). It's a reasonable request. --Mr.98 (talk) 22:13, 22 July 2011 (UTC)[reply]

Mr 98 has provided such a summary. Is there some language issue involved? The descriptions seem quite clear, if clinical and abstract. μηδείς (talk) 04:31, 23 July 2011 (UTC)[reply]

City climate website

I am looking for a website where you can enter the name of a city and it will suggest 3 or more other cities with a similar climate, but which are not nearby? I am thinking you could type in Say Rome, Italy and it would suggest Los Angeles, USA but not The Vatican City. Any suggestions? Googlemeister (talk) 20:16, 22 July 2011 (UTC)[reply]

Not sure if it has that functionality, but the Weather Underground website has lots of really good weather resources. If anywhere has what you are looking for, that would be where I would look first. See http://www.wunderground.com --Jayron32 20:25, 22 July 2011 (UTC)[reply]

Not a birch tree?

I may have misidentified the tree in these pictures. I thought the unusual bark was due to it being a very large, old birch but someone suggested it is actually a cottonwood or a poplar tree. Anyone know for sure? Beeblebrox (talk) 23:27, 22 July 2011 (UTC)[reply]

Are there any birch species that don't have paper-thin white peeling bark? This is nothing like the birch I am familiar with. Rmhermen (talk) 00:57, 23 July 2011 (UTC)[reply]

The section of forest we were in was mixed birch and spruce, with just this one tree that looked very different and was much larger. I'm pretty sure at this point that it is actually a Populus trichocarpa AKA black cottonwood. Beeblebrox (talk) 01:01, 23 July 2011 (UTC)[reply]

It is not a birch. All of them (and there are many more than the "paper birch") have bark markings that run horizontally, whereas this tree has deep vertical fissures. Bielle (talk) 01:05, 23 July 2011 (UTC)[reply]

No, its not a birch. An in focus close-up of a leaf and the location of the specimen would help. My immediate thought was "poplar" and Black Cottonwood is close, if not spot on. μηδείς (talk) 04:29, 23 July 2011 (UTC)[reply]

I might be going hiking on the same trail in the next few days, I'll see if I can manage that. The location is Diamond Ridge, Alaska, in the forest visible in this photo. I feel like the photo of the trunk didn't really capture how large it is, we don't have a lot of big deciduous trees up here and the base of this trunk had to be at least 4 feet (1.2 m) in diameter. Beeblebrox (talk) 20:38, 23 July 2011 (UTC)[reply]

Given the location, it looks like Black Cottonwood must be right, although I have never seen one. Do be on the lookout for Ents and Entwives.μηδείς (talk) 20:57, 23 July 2011 (UTC)[reply]

This close-up might help. I've never seen a big one. In the UK we call it the Western Balsam Poplar; they are sometimes planted as exotic specimens in parks etc. The leaves smell slightly medicinal IIRC. Alansplodge (talk) 00:38, 25 July 2011 (UTC)[reply]