Science desk
< March 24	<< Feb \| March \| Apr >>	March 26 >

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.

March 25

Red wine "breathing"

Does it really make a difference if you uncork a red wine bottle a couple hours before drinking it? There can't be more than a square inch exposed to the air. I can't really see how it could affect the rest of the wine. I know some people let it breath in a wide caraffe, but I know a number of wine people who will insist on just uncorking the bottle for an hour or so before serving.

Have there ever been any blind taste tests to see if people really could tell the difference between wine that has breathed or not?

James. 00:51, 25 March 2008 (UTC)

Hello James. You're right in that the small surface area from just uncorking the bottle does very little. It is somewhat of a silly practice. (Like sniffing the cork :p) However the process of decanting can have a pronounced influence on the tannins (at least the perception of them) and aroma development of the wine. The act of pouring the wine, with the motion and the splashing, will also contributes quite a bit to this aeration. While I'm not familiar with any published blind tasting test, there is an easy experiment that you can do at home. You don't need a decanter, just pour yourself a glass of wine and let it sit for half an hour. Even in that short period of time, the wine in your glass (with the larger surface area) will show some change in the aromas and flavors due to the aeration. Though do note that the extent of change will vary depending on the wine. Some wines (like Burgundies) will have more noticeable changes due to aerating than say a California Zinfandel. Agne ^Cheese/^Wine 03:14, 25 March 2008 (UTC)[reply]

It's very easy to do double-blind. Take out two wine glasses. Tell your friend to stay in the living-room. Pour one glass. Go talk to him for half an hour. Tell him to come into the kitchen for a minute...meanwhile, pour the second glass. See if he can tell which was aerated.

Sorry, to make it DOUBLE-blind, tell him to come in and see which one is aerated before you yourself know :)

Get two bottles of decent Australian Shiraz (should be around US$10-US$20 at the moment). Open one 4 hours before dinner and decant (or pour), the other directly before dinner. Be sure to keep all the wine at room temperature. Even I can taste the difference, and I'm a barbarian.The undecanted wine typically is harsh and has a slightly bitter note, the decanted one is much more mellow and fruitier. --Stephan Schulz (talk) 09:55, 25 March 2008 (UTC)[reply]

Even better, to answer James' original question: If you have a Trader Joe's market near you, buy two bottles of "Two Buck Chuck". Both should be the same grape and vintage year. Open one bottle, but don't pour it! Just let it sit open on your kitchen counter for, say, 4 hours, with the other bottle next to it to ensure both stay the same temperature. Then have a friend or family member go alone into the kitchen, open the second bottle, and pour an equal volume of each into two identical glasses, and note secretly which glass is the aired-out one. Your assistant then leaves the kitchen. You go in and taste, and see if you can detect not just a difference, but whether one tastes better than the other.

The reason I suggest Two Buck Chuck is because I have noticed that among all the wines I have bought, Two Buck Chuck experiences the most profound change, almost becoming un-drinkable a day after you open the bottle. This test will determine whether that 1 square inch of surface area makes any difference after opening a bottle. ~Amatulić (talk) 17:24, 25 March 2008 (UTC)[reply]

Even better if you can get three samples going - the unopened, the opened, and a decanted one. And then, of course, you're going to have to do something with all that wine you've just opened - sounds like an interesting dinner party experiment to me (which also means you get results from multiple people). Confusing Manifestation(Say hi!) 23:12, 25 March 2008 (UTC)[reply]

There is a small pourer which induces air into the wine as it is poured so you don't have to wait (agonising!) before drinking. Use mine every day, Hic, pardon.--Artjo (talk) 08:41, 26 March 2008 (UTC)[reply]

Hormonal Cycles In Men

Hello there! I was wondering whether men have some type of hormonal cycle at all, whether it be during certain times of day, of the week, or of the month, and where a certain hormone is more prevalent or at its peak at one moment than at others. I'm not suggesting men would have a similar cycle as the menstrual cycle in women, but I was just wondering whether there are times when a certain hormone is more active or less active.

Men have diurnal hormone cycles for such things as cortisol, ACTH and growth hormone - among others. Wisdom89 _{(_T / ^C)} 00:59, 25 March 2008 (UTC)[reply]

Melatonin is a good example. Rockpocket 06:51, 25 March 2008 (UTC)[reply]

Please read the article on Circadian rhythm. If you have any questions remaining, feel free to ask. Best wishes, --Dr Dima (talk) 12:28, 25 March 2008 (UTC)[reply]

Also, there is the GnRH --> LH --> T negative feedback loop. Basically, the hypothalamus (little gland in the brain) releases an hormone called GnRH that tells the pituitary gland (another little gland in the brain) to release a hormone called LH. The LH then proceeds to the testes and tells them to secrete testosterone (T), a steroid hormone with which we are all familiar. But then the testosterone, circulating through the blood, tells the hypothalamus to stop secreting GnRH, which in turn slows down LH production, which in turn slows T production, which permits GnRH secretion again... This is a classic negative feedback loop with a period of, if memory serves, roughly four hours, and again if memory serves this does result in periodic peaks and troughs of adrenaline, which can have both physiological and psychological effects. See [[1]], for example. It is analogous (or homologous) to the female GnRH --> FSH --> E/P cycle. It also bears mention that men have been reported (though the homology is subject to controversy) to undergo "andropause" after middle age. Vance.mcpherson (talk) 13:37, 25 March 2008 (UTC)[reply]

How do I become a stuntman?

I love Jackass and Dirty Sanchez. I like doing extreme, painful stunts to impress my friends (found something that I'm good at). How do I get to be on TV like those guys? I don't wanna be just another one of those guys who posts his stuff on YouTube and gets called a reckless idiot. I want to be a reckless idiot on TV.

You must have an exceptional pain threshold that can be put to good use. There's stuntschool.com in the USA here[2] and googling "stunt man training" gets you lots more stuff you might like – our articles stunt performer, stunt double and stunt coordinator look brief. Otherwise popping this whole thing onto the entertainment desk might get more details. Please sign your posts with four ~ and good luck, Julia Rossi (talk) 02:05, 25 March 2008 (UTC)[reply]

Hanging swamps

I'd like to start an article on hanging swamps but can only find a few things on google limited to the Blue Mountains outside of Sydney and on wikipedia, only to one in particular though there are more. Does anyone have references they could suggest? Are they found in other parts of the world as well? Thanks, Julia Rossi (talk) 02:08, 25 March 2008 (UTC)[reply]

SOunds like they would have another name - perhaps alpine meadow. In the ACT a sphagnum bog is the source for the Cotter River. Graeme Bartlett (talk) 03:52, 25 March 2008 (UTC)[reply]

Superficially they look like a combination of both. The trees only come to the edge of it, and it's on a slope rather than level ground, without many rocks. Julia Rossi (talk) 07:33, 25 March 2008 (UTC)[reply]

online versus offline wetlands

What is the definition of an online wetland? I expect it has something to do with being in a drainage line but where is the line drawn in terms of the hydrologic capacity of an online versuus offline wetland?

Yeah, I think has something to do with how it drains (online=draining, offline=not draining, most of the time). I don't know where I picked that up, though. But I believe it has nothing to do with the amount of WiFi access within the area tho :P ~user:orngjce223 how am I typing? 16:48, 26 March 2008 (UTC)[reply]

Atomic Force Microscopy

I've got an assignment on AFM and one of the questions relates to metal nanoparticles on a teflon coated magnetic stiring bead and how to image them. I'm a bit ^stuck with how one would go about imaging this as the surface needs to be quite flat. Would it simply be a matter of cutting a piece of the stirrer bead off and flattening it with a press of some kind? Any other ways in which the stirring bead can be flattened so that it can be imaged? How flat would it need to be? Thanks --Shniken1 (talk) 05:22, 25 March 2008 (UTC)[reply]

I wouldn't suggest flattening it as that could significantly change the structure. Instead, you need to cut a very narrow slice and put it on a slide. StuRat (talk) 06:31, 26 March 2008 (UTC)[reply]

What model Saab is this?

1
2
3

I can't ID it from the Saab article, but am guessing it's one of the older models. BrokenSphere^{Msg me} 05:37, 25 March 2008 (UTC)[reply]

Hi Brokensphere, I found something like it here[3] of a 96V4 also butterscotch coloured, but doesn't give the year. Julia Rossi (talk) 07:08, 25 March 2008 (UTC)[reply]

Ps, if you scroll down further to the white one, they put it at 1970. Cheers, Julia Rossi (talk) 07:10, 25 March 2008 (UTC)[reply]

It looks like a Saab 96 - see especially the picture of the 1965 model near the bottom of the article. Are you sure this is a science question? 84.239.133.86 (talk) 07:56, 25 March 2008 (UTC)[reply]

Or maybe a Saab Sport given the chrome striping at the bottom (although strictly speaking it should be a double stripe, unless one's been lost - see here). I don't think the 96 had any chrome stripes, unless they added them later. --jjron (talk) 10:00, 25 March 2008 (UTC)[reply]

Stuck in fetal position?

When I was much younger... something like 12, I woke up one morning and couldn't get out of the fetal position. It hurt one of my hips (maybe a hip flexor muscle) so much when I tried to straighten that leg out that I had to straighten up slowly over the period of about half an hour it seemed. I'm not asking for advice, just a list of possible things that might have caused this, or any other insights... but no advice please. Sancho 06:23, 25 March 2008 (UTC)[reply]

Muscle cramp? Dismas|^(talk) 09:02, 25 March 2008 (UTC)[reply]

Stupidity? Weasly (talk) 12:21, 26 March 2008 (UTC)[reply]

Given the following two premises: (1) a large body of science fiction which creates a connection between pregnancy, fetuses, and alien abduction, and (2) the existence of sleep paralysis and its supposed explanation for alien abduction; is it possible you are or were a character in a science fiction novel? Nimur (talk) 14:42, 26 March 2008 (UTC)[reply]

Battery life meter

One of the more annoying "features" of my cell phone is that the battery life meter doesn't tell you how much life is left in the battery. It tells you how much is left if you continue doing whatever it is that you're doing with the phone until the battery is depleted. So if I just open the phone up, I could have 3/4 of a charge. If I start taking photos and sending them to my friends, the battery indicator goes down rather quickly and sometimes even causes the phone to warn me that the battery is running low. Although if I close the phone and re-open it, I again have 3/4 charge. Is there a term for this sort of battery meter other than annoying? Dismas|^(talk) 08:26, 25 March 2008 (UTC)[reply]

"Typical" :-). But I'm not sure what you want it to do. A battery life meter can't give you some sort of absolute measure of how much time it's got left, because that's dependant on the usage, especially for something like a mobile phone with a small battery and high fluctuations in demand. If you were doing something like playing a radio on batteries where the current draw was constant, an absolute measure would be more feasible. If anything this is a 'smart meter', because it's detecting your current usage and adjusting the available life shown on the meter accordingly. --jjron (talk) 09:44, 25 March 2008 (UTC)[reply]

This reminds me of the Rand McNally GPS unit I had. It would estimate my ETA based on my current speed, not on the average speed of the trip so far. The result was that when I stopped at a traffic light it said the trip would take an infinite amount of time to complete. StuRat (talk) 06:27, 26 March 2008 (UTC)[reply]

Did it actually use the infinity sign? If so then I must credit the programmers/engineers for having a sense of humor--droptone (talk) 11:35, 26 March 2008 (UTC)[reply]

No, it said something like 9999 minutes, the largest number it could display. StuRat (talk) 13:53, 26 March 2008 (UTC)[reply]

Hey, it could be worse. My cell phone won't tell me what time it is if it loses signal. I'm all for it checking it dynamically with the tower and updating as necessary, but totally being unable to tell time without a signal? Terrible design. --Captain Ref Desk (talk) 13:02, 26 March 2008 (UTC)[reply]

Axes of rotation, revolution, magnetic field, of the earth

Among the axes of rotation, revolution around the sun, and magnetic field, of the earth, which are parallel to each other, and which are not? Why are they parallel (or not)? --Masatran (talk) 09:44, 25 March 2008 (UTC)[reply]

See Earth's rotation for starters. The diagram Image:AxialTiltObliquity.png is quite simple to interpret for the relationship between rotation and revolution. For 'why', particularly see the section Origin of rotation and the pages that links to. See Earth's magnetic field for the magnetic field - it is close to the geographical rotational axis, but not the same. --jjron (talk) 10:18, 25 March 2008 (UTC)[reply]

As for why the magnetic poles don't match the North and South Poles, I believe that is because the Earth's composition is neither uniform nor static. Different materials conduct the magnetic field better than others, which deforms the field slightly. Interestingly, the magnetic poles aren't necessarily on the exact opposite sides of the Earth, vary over time, and even invert over long time periods, ty[pically after a long period of instability. StuRat (talk) 06:24, 26 March 2008 (UTC)[reply]

Effect of elliptical orbit of earth on climate

The distance of the earth from the sun changes over the year because the orbit is elliptical. What effect does this have on the climate of the earth? --Masatran (talk) 09:53, 25 March 2008 (UTC)[reply]

Some of the ice ages are thought to be one consequence. Check out Milankovitch cycles. 88.114.125.67 (talk) 10:24, 25 March 2008 (UTC)[reply]

The effect should have a time period of one year, right? It will be hotter when the earth is closer to the sun, and colder when the earth is further away from the sun. Is this effect present? And what is this effect called? --Masatran (talk) 10:31, 25 March 2008 (UTC)[reply]

Seasons? Dismas|^(talk) 10:35, 25 March 2008 (UTC)[reply]

When I was a kid, I thought likewise. But now I know that seasons are caused by the inclination of the north (or south) pole towards the sun. --Masatran (talk) 10:52, 25 March 2008 (UTC)[reply]

Masatran is right. There's a very easy way to see this. The effect of an elliptical orbit would be to make the whole earth warmer or cooler. The effect of an orbital tilt will be to make the northern hemisphere warmer while it makes the southern hemisphere cooler. (And vice versa six months later.) As the Season article points out, it's the latter we observe: "At any given time, regardless of season, the northern and southern hemispheres experience opposite seasons." JohnAspinall (talk) 13:52, 25 March 2008 (UTC)[reply]

The Earth is slightly hotter at perihelion than at aphelion, and this is a one-year period (give or take, I think there's some precession thrown in there as well) as you surmised. However, any effects are dwarfed by the changes resulting from the Earth's axial tilt (that is, seasons). If I recall correctly, aphelion corresponds roughly with northern summer and southern winter. — Lomn 13:06, 25 March 2008 (UTC)[reply]

That is correct. I've heard that this, along with the presence of the gigantic Antarctic ice cap, makes Southern Hemisphere winters colder than Northern Hemisphere ones at the same latitude.

I don't think it is true that northern winters are warmer than southern ones. A quick comparison of the latitudes of North American cities to southern Australian ones shows the opposite is true, c.f New York City with Melbourne or Hobart. I don't know how representative this is though.--Shniken1 (talk) 23:20, 26 March 2008 (UTC)[reply]

According to our article, "Climates in the southern hemisphere overall tend to be slightly milder than those in the northern hemisphere except in the Antarctic which is colder than the Arctic. This is because the southern hemisphere has significantly more ocean and less land. Water heats up and cools down more slowly than land." I guess I was thinking of the antarctic/subantarctic regions, which are definitely colder. Vultur (talk) 20:52, 29 March 2008 (UTC)[reply]

In terms of insolation, the difference between aphelion and perihelion is about 6%. At 40° latitude, there's a factor of about 2.1 in insolation comparing winter and summer solstices. Icek (talk) 14:45, 29 March 2008 (UTC)[reply]

Concentrating DNA samples

If I have DNA which I want to concentrate 2.5x, could there be a problem with, say storing the tubes open in a container with some of those sodium silicate dissicating crystals to lower humidity? They can't be run through a column because that's where they've been already and that process involves too much loss. --145.29.23.38 (talk) 11:22, 25 March 2008 (UTC)[reply]

Why not do a standard ethanol precipitation of the DNA and resuspend the dried pellet in a smaller volume? it won't take more than half an hour or so. -- Flyguy649 ^talk 15:43, 25 March 2008 (UTC)[reply]

Never done it before (I'm just a lousy intern) - I'll ask my supervisor if we can do that. Thanks very much :) --145.29.23.38 (talk) 17:00, 25 March 2008 (UTC)[reply]

Fairly simple. Just increase the volume of your DNA sample with Tris buffer (doesn't have to be much). Add 3-5 volumes of either cold isopropanol or ethanol and centrifuge for 30 minutes at 15,000 RPMs (JA-20 rotor) or 12,000 RPMs in a microfuge depending on the size your sample. When the pellet is present, simply redissolve it in 2.5x's less Tris buffer. Wisdom89 _{(_T / ^C)} 18:48, 25 March 2008 (UTC)[reply]

Or you could check if there is a vacuum centrifuge in the building (no article yet, but is basically spins the DNA while evaporating the liquid. Rockpocket 07:19, 27 March 2008 (UTC)[reply]

Dutch tulip forecast

It has been snowing and cold in Holland all through the Easter weekend, and beyond. Can anyone refer me to a website with a forecast for the 'peak' of the 2008 tulip season. It must change...with the weather, I would think. Presumably as the weather stays cold, the peak moves further into April. Thanks if you can show me to a reference where I can get an estimate for the peak days/weeks.

The scientific method

How do scientists find out about the updates and changes in the earth's crust? What are the technolgies needed to find out about the structure/different layers of the earth?

You'll probably want to start with the Composition and structure section of our article on the Earth and work out from the links there to get all the details. TenOfAllTrades(talk) 16:15, 25 March 2008 (UTC)[reply]

You can also look at the geology, Plate tectonics and stratum articles. Sandman30s (talk) 14:24, 26 March 2008 (UTC)[reply]

Don't forget to read about seismic waves. Seismometers are essential instruments (technology) and by comparing the readings at different locations, we can infer the structure of the earth. Nimur (talk) 14:45, 26 March 2008 (UTC)[reply]

Mobile Phone Noise

First of all, I live in the UK, which I guess may be relevant.

When I leave my mobile phone next to seemingly another peice of electrical equipment, there is a noise which prempts text messages and calls. My tv, computer, hi-fi, anything.

It's that strange "du duh-de-duh duh-de-duh" noise (which I put into Google, but alas...) What causes it and why does it show up on everything, even things that wouldn't be thought to be interferred with my a mobile's signal? A good example of that would be through my Ipod, and out of my earphones.

Thanks a lot. Fenton Bailey (talk) 16:04, 25 March 2008 (UTC)[reply]

Every time your telephone communications with a central cellular tower (when you have an incoming call or message, or periodically when the phone handshakes with the tower) it broadcasts a fairly strong radio signal. The wires of your headphones, speakers, stereo, or television act as (not-very-good) antennas which pick up some of that radio signal and overlay it on top of whatever else you're listening to. TenOfAllTrades(talk) 16:13, 25 March 2008 (UTC)[reply]

I have found the effect is more severe when the phone is near an amplifying device (powered speakers, for example); this suggests that the cell phone's RF transmissions may couple directly into the amplifier, rather than the feed wires as antennas. Surely it's some combination of the two. Nimur (talk) 14:48, 26 March 2008 (UTC)[reply]

That is correct. I use this little fact to tell my friends their phone is about to ring by paying attention to the car radio, they still haven't figured out how I do it. 206.252.74.48 (talk) 16:59, 25 March 2008 (UTC)[reply]

Heh, I do that too. They ask how do I do it, and I just say "nerd-sense". — Kieff | Talk 01:31, 26 March 2008 (UTC)[reply]

Electromagnetic interference.--Shantavira|^{feed me} 17:40, 26 March 2008 (UTC)[reply]

Why do deep footprints in snow look blue?

I was walking in the snow with my daughter today, and we had to cross some deep drifts, where our feet sunk over a foot into the snow. When we looked into the holes there was a distinct blue tinge, though the snow itself was white. My daughter asked me why this is, and I didn't know. Pools of melt-water were crystal clear, with maybe a slight greenish tint but that could have been because of the grass at the bottom, so it is not because of absorption by the water, unless it acts differently as ice. -- Q Chris (talk) 18:21, 25 March 2008 (UTC)[reply]

I don't know if this is the explanation, but water is a bit blue. See color of water. Ahh, here we go- one of the references used in that article is this which I think is pretty relevant. Friday (talk) 18:24, 25 March 2008 (UTC)[reply]

If the surface of the snow was in direct sunlight, the bottom of your footprint could look blue because it is shadowed by the wall of your footprint. Outdoor shadows look blue because they are illuminated by the blue sky, a phenomenon that photographers will be familiar with. I have found the color difference to be very noticeable on snowfall. -- Coneslayer (talk) 18:45, 25 March 2008 (UTC)[reply]

Indeed, red is scattered less than blue by the atmosphere, so a larger fraction of red (than of blue) comes straight along the direction from the sun, and smaller fraction of red (than of blue) comes from the other directions. If the hole walls block the direct sunlight, the bottom of the hole will be illuminated by the light which has a larger fraction of blue (compared to the fraction of blue in the white light, that is, the light you see on the snow that is illuminated from all directions). So the snow is not blue, it is white; rather, the light illuminating it is relatively rich in blue. On the other hand, water and transparent ice are genuinely blue, see blue ice (glacial). --Dr Dima (talk) 20:58, 25 March 2008 (UTC)[reply]

Quantum Number Sets

The quantum numbers article (http://wiki.riteme.site/wiki/Quantum_numbers) says that the magnetic quantum number should be between the negative and positive values of the azimuthal quantum number.

If I come across the notation 3d₄,+1/2 or 5f₅,-1/2, would those be considered wrong? Because d=2, so the magnetic quantum number should be between -2 and 2, so 4 doesn't make sense. Same with f being 3 so 5 doesn't fit between -3 and 3. -- Zealz (talk) 23:49, 25 March 2008 (UTC)[reply]

That's correct. Those symbols don't refer to any real states. —Keenan Pepper 02:41, 26 March 2008 (UTC)[reply]