Wikipedia:Reference desk/Archives/Science/2008 February 24

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February 24

Here comes the sun

I have read the wikipedia article on that great celestial body, but I did not found the information I seek.

If the sun is mostly mad up of gases and plasma--how does it have as much mass as it does? That is, gases and plasma are not very dense in my understanding, and yet the sun has enough mass to keep the entire solar system in check. What am I missing, or is merely a case of "yes, gases have a low density, but there's just so damn much of it!" —Preceding unsigned comment added by 192.136.22.4 (talk) 02:23, 24 February 2008 (UTC)

It's a matter of mass in terms of quantity (of gas/plasma molecules) and the size of the star, but also the fact that the core is dense. Wisdom89 _{(T / ^C)} 02:28, 24 February 2008 (UTC)

Gasses do not have to have low density. This perception results merely from the tendency of gasses on Earth to have low density. At extremely high temperatures and pressures, gas can be incredibly dense. Indeed, the average density of the sun is greater than that of water (density of water is about one gram per cubic centimeter), although the precise value of density depends on distance from the center. At the core itself, the density of the sun is an incredible 160 grams per cubic centimeter, which is much denser than even solid metals (uranium, denser than even lead, has a density of only 19 grams per cubic centimeter). Once again, these densities are possible in the sun due to extreme temperatures and pressures. Someguy1221 (talk) 02:57, 24 February 2008 (UTC)

It's also partially a matter of "there's just so damn much of it". If you add the volumes of the planets, you'd get 2.39 x 10^15 m^3. By comparison, the Sun's volume is 1.4122 x 10^18 m^3, about 600 times larger. --Bowlhover (talk) 04:15, 24 February 2008 (UTC)

The sun is approximately on average 1.4g/cm³, about 108 Earth diameters, and you probably didn't need to know any of that because you could probably find it in the article and I'm probably innacurate anyway. Hope this helps. Thanks. ~AH1^(TCU) 00:42, 26 February 2008 (UTC)

Breitling Orbiter 3

Hello. The world's first round-the-world balloon flight was on March 1, 1999. Couldn't the flight take place during the summer so that Chateau d'Oex becomes closer to the jet stream? Thanks in advance. --Mayfare (talk) 05:18, 24 February 2008 (UTC)

Many factors went into the decision to launch the balloon at that time, not the least of which were purely human logistics (when the pilots were available, when the equipment and ground stations were ready, ... ) You might want to read up on launch window for a general discussion on choosing the best launch time based on scientific as well as practical constraints. All of engineering can be summarized as systematic study of tradeoffs ... Nimur (talk) 22:31, 27 February 2008 (UTC)

Human genome conservation with dogs

Does anyone know how conserved the human genome when compared to the dog genome? I should know how to do this, but for the life of me I can't remember how to use NCBI's website to do a genome comparison. Anyknow know how genetically similar we are compared to dogs?

According to this source, dogs share 95% of their genes with humans.[1] MrRedact (talk) 07:13, 24 February 2008 (UTC)

Haha, is it actually true that we share 50% of our DNA with bananas? That's wonderfully absurd if true, although I have to admit, I have no clue what it means at the moment. -- Aeluwas (talk) 12:54, 24 February 2008 (UTC)

I find that 50% human/banana overlap apeeling. Edison (talk) 13:55, 24 February 2008 (UTC)

"In Tahiti an old Polynesian chief explained his diet: 'The white man, when well roasted tastes like ripe banana.'"Vintage School 4.1. There you are! Pro bug catcher (talk • contribs). 14:47, 24 February 2008 (UTC)

Which of your parents is it, that you claim is descended from a banana? (apologies to Sam Wilberforce). SpinningSpark 20:31, 24 February 2008 (UTC)

Oh, the painful punniness of it all. Yes, we share a large amount of our DNA with other eukaryote (and even quite a bit with prokaryotes. At the molecular level or proteins and lipids and whatnot, we're really strikingly similar. Yes, even with plants. – ClockworkSoul 21:49, 25 February 2008 (UTC)

RNA amplification

I know you use PCR to amplify DNA, is there a process similar to PCR which you can use to amplify RNA? —Preceding unsigned comment added by 70.49.175.36 (talk) 06:04, 24 February 2008 (UTC)

RTPCR. — Scientizzle 06:51, 24 February 2008 (UTC)

Question about Salmon (but don't Rushdie answer)

Salmon die shortly after mating, but what is the exact mechanism of this death ? Does their immune system shut down, allowing disease to finish them off ? StuRat (talk) 06:38, 24 February 2008 (UTC)

Their swim upriver drains their fat stores and generally exhausts them, leaving them open to injury, disease, or parasitism. The "after spawning" section of this article notes that they don't all die, and those (few) that manage to survive can return to nominal health and even spawn again. -- 19:23, 24 February 2008 (UTC) —Preceding unsigned comment added by Finlay McWalter (talk • contribs)

Thanks, that article seems to say that male Atlantic salmon die because they remain in the spawning area to mate repeatedly, draining their energy stores until they die, but that many females do survive. It didn't really talk about Pacific salmon, though, other than to imply that they all die. Do we know what causes this ? The Chinook_salmon#Reproduction section seems to say that they die because they stay around to "guard the eggs", until they die. Is this true of all Pacific salmon ? StuRat (talk) 20:33, 24 February 2008 (UTC)

Ha ha, funny heading title. My compliments. —Lowellian (reply) 19:28, 24 February 2008 (UTC)

Thanks. :-) StuRat (talk) 20:33, 24 February 2008 (UTC)

Pacific salmon certainly don't "guard the eggs". All Pacific Salmon, I believe, die shortly after spawning--it's a sort of built-in death. There is an interesting article [2] that sees some similarities between this and Alzheimers.--Eriastrum (talk) 21:24, 24 February 2008 (UTC)

That article is quite useful, thanks. It looks like the process isn't yet completely understood. Is the statement "After laying eggs in a redd, adult Chinook will guard the redd from 4 to 25 days before dying." incorrect in our article: Chinook_salmon#Reproduction ? Perhaps it should say "remain in" instead of "guard" ? StuRat (talk) 23:29, 24 February 2008 (UTC)

I think that the female guards the redd until she lays the eggs and the male fertilizes it. Then she goes on to make another redd. I thus don't think that it is correct to say that she guards the eggs as such. I can't vouch for its accuracy, but this article seems to have relevant information [3]. Maybe salmon aren't fat(wa) enough to live longer (sorry).--Eriastrum (talk) 00:42, 25 February 2008 (UTC)

Thanks, but that article did seem to say the females guard the redd, but not the males. Iran directly to our article to make the correction. StuRat (talk) 01:50, 25 February 2008 (UTC)

Photon bouncing?

Inspired by this, if we have 2 identical space ships with perfect reflectors on the back going on opposite directions, and one shoots a beam of laser to the other one, what will eventually happen to the photon? What happens when it gets so red-shifted that it's no longer stable (there is a lower bound on its frequency right?)? --antilived^{T | C | G} 07:38, 24 February 2008 (UTC)

Hmm, why do you think red-shifting will eventually make the photon unstable? There is no lower bound to frequency and if the reflectors are perfect as you specify and the transmission medium is perfect it will bounce back and forth forever.

Of couse, in practical terms there are any number of things that could eventually lose a given photon out of the system. If nothing else, it would eventually be red-shifted so far that the wavelength is large compared to the size of the reflector and will then fail to be reflected and carry straight on past the space ship. However, your space ship will probably have broken down and decayed long before then. SpinningSpark 12:14, 24 February 2008 (UTC)

So there is no lower bound on the frequency? Can a photon with the wavelength of more than the universe exist? --antilived^{T | C | G} 05:58, 25 February 2008 (UTC)

There is no limit, not up not down. There can't be - it would violate conservation of energy. But with a wavelength below the Planck length it is not calculable using current physics. The universe does not have a fixed size. Even if it's bounded, it would probably wrap around, so a photon could be as big as it wants. It 'feels' like it should have some weird properties when it's so big, but I can't think of any. Perhaps the uncertainty principle would do something strange to it. Ariel. (talk) 12:52, 25 February 2008 (UTC)

Bit shaky on my quantum mechanics (its been a long time) but I would guess a photon that was that big would be experiencing destructive interference as in DeBroglie wavefunctions for an electron in a Hydrogen atom. That is, it can only exist if it is exactly the right size or a harmonic. Ariel is right that there is no limit in free space, but in a bounded situation everything becomes quantized because of standing waves in the wavefunction. Or possibly I am just talking unsubstantiated OR, I have never seen anything written on photons that big. SpinningSpark 14:01, 25 February 2008 (UTC)

Even this 305 meter parabolic reflector is "transparent" at low frequency radio waves on the order of hundreds of hertz, so if you want to beam such waves into the sky for some reason, you have to modulate them at the higher frequencies this reflector can handle. Note that the energy is emitted from the horn and beamed down, then reflected back up to the sky. Nimur (talk) 22:40, 27 February 2008 (UTC)

Fortunately, practical considerations will save us from wacky breakdown of the laws of physics! You won't be able to reflect the photon indefinitely. As it becomes more redshifted, it will have a longer wavelength with respect to your "mirror" aperture and it will eventually have such a long wavelength that your "reflector" will be entirely transparent. It doesn't matter how big you make your mirrors. Once the photon disperses to (sufficiently larger than) that size, you won't be able to redshift/reflect/focus it anymore with that mirror. Nimur (talk) 22:35, 27 February 2008 (UTC)

Boiling oil

what happens when you boil oil? The Updater would like to talk to you! 11:04, 24 February 2008 (UTC)

I'm not sure I understand the question. Obviously, when you boil anything it transitions from a liquid to a gas, but I suspect your question is about something specific about oil. StuRat (talk) 14:40, 24 February 2008 (UTC)

Also, what kind of oil? Motor oil, cooking oil, sewing machine oil? Delmlsfan (talk) 15:27, 24 February 2008 (UTC)

Howstuffworks has a nice illustration of the range of boiling points for petroleum products. Note also that, in a standard atmosphere, most oils begin to burn well below their boiling points. — Lomn 15:49, 24 February 2008 (UTC)

Too bad that isn't true of cooking oils. That might prevent us from frying our food in it. :-) StuRat (talk) 20:19, 24 February 2008 (UTC)

That is true of cooking oils—deep fryers are used at temperatures well below the boiling point of most edible oils. (The key criterion in choosing an oil for deep frying is the oil's smoke point; boiling point is never considered.) TenOfAllTrades(talk) 23:47, 24 February 2008 (UTC)

Then there must be a great deal of confusion among chefs, since I found 728 Google hits, most of which appear to be recipes that instruct the cook to bring oil to a boil: [4]. StuRat (talk) 01:35, 25 February 2008 (UTC)

I don't think it's so much confusion among chefs as it is confusion among idiot web page authors. Chefs (and cooks with even a modicum of common sense) are well aware that oil is not boiled in cooking. That, in fact, is one of the dangers - 350°F oil is visually indistinguishable from room temperature stuff. The confusion probably has roots in water's well-known and much lower boiling point, which comes into play when food is added to the fryer -- any water present quickly boils, which is responsible for all the hissing, popping, and so forth. — Lomn 14:24, 25 February 2008 (UTC)

But most of the directions say something like "bring the oil to a boil, then add the food", so what would make them think the oil was boiling before the food has been added ? StuRat (talk) 02:28, 26 February 2008 (UTC)

Objectively? Nothing. Absolutely nothing suggests that 350°F oil would be "boiling" except for the possibility that somebody says "350? That would boil water! OK, then, 'boiling'!" (Never mind, of course, that water can't hit 350°F either). Thus, I'm blaming the web page author, or perhaps more appropriately should blame people who don't understand "boiling". Note, for instance, specifically phrased Google hits: "heat oil to a boil" gets 3, "bring oil to a boil" gets 12, and "heat oil to 350" gets 586. The vast majority of cooks understand that oil is not boiled when cooking. — Lomn 14:30, 26 February 2008 (UTC)

I clicked on your link for "bring oil to a boil" and got 703 hits, not 12. (I've asked before about why different people get radically different Google results when doing the same search, but never did get a satisfactory answer.) The recipes are often for cooking on the stove, and no temperature is mentioned, so they must be instructing people to heat the oil until something visible happens that can at least be confused with boiling. StuRat (talk) 05:51, 27 February 2008 (UTC)

Perhaps it's a matter of making sure you've counted all actual results? I run Google with 100 English-only results returned as a default, and while I list 586 returns for "heat to 350", Google's initial estimate for that query is 11.3 million. However, the bit about the oven is what I addressed above regarding the dangers of oil: until you reach the smoke point (often around 400°F for cooking oil, at which point it is chemically breaking down and worthless for cooking) there is no obvious distinguishing visible factor. Hot oil displays miniscule ripples (which I think are actually atmospheric distortions from the heat, not actual surface displacements in the oil), but we're talking about something with an apparent displacement of less than a millimeter and relatively static. Nothing at all about hot oil resembles boiling water in any way until you add water to the pot. — Lomn 14:23, 27 February 2008 (UTC)

Perhaps your question is about spattering of cooking oil when food is poured in. This can happen if there is water or ice on the food, which then turns into steam and can launch droplets of oil out of the pan with it. To prevent this, make sure the food is dry before you place it in boiling oil. Splashing of the oil is also possible if food is dropped in. To prevent this, slowly lower food into boiling oil with a fry basket. StuRat (talk) 20:56, 24 February 2008 (UTC)

Of course, in the popular mind, boiling oil is associated with medieval siege defence. Despite what you might read there, or in a lot of websites or books, boiling oil was not used for this purpose. Crude oil was used in Greek fire, and the Romans were known to have used hot oil on a few occasions (but it was not very common). The main use of murder holes was boiling water: easier than oil, cheaper, less dangerous, more plentiful, very effective. I think the popular mind has just merged "boiling water" with "oil", a situation not helped by a few Hollywood movies. -Gwinva (talk) 01:03, 25 February 2008 (UTC)

Apologies if it's impolite to add on to someone else's question, but is it true that lime was also used? AlmostReadytoFly (talk) 09:27, 25 February 2008 (UTC)

Yes. I'll hunt the details out if you're interested. Gwinva (talk) 09:29, 25 February 2008 (UTC)

Thanks, but no. It's enough that I know I hadn't imagined reading that somewhere. AlmostReadytoFly (talk) 10:41, 25 February 2008 (UTC)

Shouldn't that article be updated to say that oil doesn't actually boil? :D\=< (talk) 17:17, 25 February 2008 (UTC)

Yes, so I've done it by moving it to Early thermal weapons (since I couldn't think of a better title), ditching most of it then rewriting with the stuff about sand, water, quicklime etc. If any of you science buffs can add a reference for the smoke point of oil being lower than boiling point, that would be great (otherwise someone is bound to cn-tag it at some point!). Gwinva (talk) 00:30, 26 February 2008 (UTC)

One product produced is Acrolein contained in the smell of burnt fat. Graeme Bartlett (talk) 12:25, 25 February 2008 (UTC)

Hi, I'm sorry I couldn't be a bit more clearer. I needed to know about the lipids in oil - what happens in regards to them? But hey, thanks for the great tips and clarification. The Updater would like to talk to you! 08:29, 28 February 2008 (UTC)

Salinity of saline solutions

How salty are sweat, tears and that stuff that you use to soak your contact lenses compared to, like, the ocean?--The Fat Man Who Never Came Back (talk) 15:09, 24 February 2008 (UTC)

The salinity of sweat is examined in this paper by Bulmer and Forwell. It depends on the sweat rate, but seems to be between 30 and 120 milli-molar equivalents per litre. Sancho 15:23, 24 February 2008 (UTC)

The salinity of seawater is about 3.5%. Most of that's sodium chloride. Tears have the same osmolality as the body's internal fluids, containing a mixture of salts. (An isoosmotic solution of sodium chloride – as used in normal medical saline solution – contains about 0.9% sodium chloride: about 150 millimolar.) TenOfAllTrades(talk) 17:13, 24 February 2008 (UTC)

salinity of bodily fluids is the same as the salinity the ocean was, when our distant ancestors crawled out of it; they had to carry that environment around with them for their cells to function. meanwhile, however, the earth continued to wash minerals down off the land into the ocean, so that now it is much saltier than it was then, and than we are; and the organisms that stayed behind have had to adapt to that.Gzuckier (talk) 18:27, 26 February 2008 (UTC)

The same as when our ancestors crawled out of the ocean? Are you sure? Wouldn't it be more likely to be the same as when cellular life forms established a clear separation between what was inside and what was outside the cell, i.e. some two billion instead of 500 million years ago? Or possibly when multicellular life evolved? See Timeline of evolution. I was unable to find any source internally or externally about rate at which ocean salinity has risen. Is anything known at all on such large time scales? --NorwegianBlue ^talk 20:41, 26 February 2008 (UTC)

Ocean life is good at expelling salt from the interiors of their cells. I think a better scientific explanation is that there is an ideal salinity for certain biochemical processes, and the cell tries to maintain that level. Nimur (talk) 22:46, 27 February 2008 (UTC)

Thank you. And now for another salty question....

Other salts

Do all salts taste "salty?" Are there any edible, nutritious salts besides NaCl?--The Fat Man Who Never Came Back (talk) 17:49, 24 February 2008 (UTC)

'Nutritious' is a matter of quantity. Chronic excess consumption of sodium chloride is linked to high blood pressure, heart disease, and other ailments. Acute overdoses of sodium chloride can be fatal.

To answer the question you're probably asking, potassium chloride is often used as a salt substitute for individuals on sodium-restricted diets. Its oral toxicity is quite low (comparable to that of sodium chloride). TenOfAllTrades(talk) 17:56, 24 February 2008 (UTC)

What are the most toxic salts? Are they salty as well?--The Fat Man Who Never Came Back (talk) 18:01, 24 February 2008 (UTC)

You'll have to test and report back.

On a somewhat more serious note, there are a lot of different salts, and they will have a wide range of tastes. Salts of zinc reportedly have a bitter, astringent flavour. Cyanide salts have an odour of almonds—tasting is discouraged. Calcium carbonate is the bulk of most calcium antacids; it has a chalky taste. Sodium citrate is acidic and tart. Alkaline salts may have a soapy taste or mouthfeel. The list is practically endless. TenOfAllTrades(talk) 19:24, 24 February 2008 (UTC)

Also see Taste#Saltiness, which could use references. --Allen (talk) 20:19, 24 February 2008 (UTC)

I stumbled upon a paper on this subject recently, but I'll be damned if I can remember what keywords I was searching the journals with. If I recall, it's the chloride anion which actually triggers the "salty" flavour, and different counterions (sodium, potassium, etc.) affect how strongly salty something may taste. If I find the article, I'll get back to you. Sockatume (talk) 01:37, 25 February 2008 (UTC)

check out Sea Salt. That tends to have all kinds of salts mixed up in it. Furmanj (talk) 01:54, 25 February 2008 (UTC)

Also check out Salt (chemistry)#Tastes. Sockatume: from personal experience, potassium chloride tastes much saltier than sodium chloride and has a very unpleasant aftertaste. Calcium carbonate has no taste. Potassium nitrate, the main component in gunpowder, tastes slightly alkaline. Sodium bicarbonate, baking soda, also tastes alkaline and sodium carbonate is unbearably so. Lithium oxide turns into lithium hydroxide upon contacting water, and therefore tastes very caustic. Iron oxide is obviously tasteless. Again, all of this is from personal experience and may not be reliable. --Bowlhover (talk) 06:42, 25 February 2008 (UTC)

Other edible salts include Epsom salts and sal ammoniac. Magnesium chloride tastes more salty than salt, and Calcium chloride is pretty harmless. potassium sulphate and sodium sulphate taste less salty but are also harmless in small quantities. PS don't eat lithium oxide or lithium hydroxide as they are very damaging to flesh. Graeme Bartlett (talk) 12:18, 25 February 2008 (UTC)

Yes, don't eat sodium carbonate either. It is used as washing soda and tastes extremely, extremely alkaline. --Bowlhover (talk) 17:26, 26 February 2008 (UTC)

That is superb--tasting notes for salts of every sort. I love the Science reference desk.--The Fat Man Who Never Came Back (talk) 02:21, 26 February 2008 (UTC)

There was an episode of Good Eats that focused on salt, it aired back in 2004. Alton Brown talked about all the different kinds of salts depending on where they come from, how they're processed, etc... -- MacAddct  1984 ^{(talk &#149; contribs)} 15:03, 25 February 2008 (UTC)

I love Alton Brown. But I'm sure he was talking about different kinds of table salt. I was asking about different types of chemical salts.--The Fat Man Who Never Came Back (talk) 02:21, 26 February 2008 (UTC)

See also Monosodium glutamate (MSG), also known as E621. It is used as a food additive because it stimulates the umami taste receptors. I heard a story on this podcast that suggested a link between the huge increase in the consumption of MSG and the obesity epidemic, based on studies in rats, but according to our article, this correlation was not found in humans. --NorwegianBlue ^talk 22:02, 25 February 2008 (UTC)

I am confused by the claim that iron oxide is flavorless. Rusty nails taste different from plain nails, and the difference is iron oxide. Edison (talk) 05:30, 26 February 2008 (UTC)

Sorry, iron oxide is not flavourless. It has a mild taste that I can't accurately describe; it's been a long time since I've tasted rust. --Bowlhover (talk) 17:26, 26 February 2008 (UTC)

Salts of heavy metals such as lead are very toxic (often more toxic than the pure metal). See Lead(II) chromate, for example.Nimur (talk) 22:47, 27 February 2008 (UTC)

Coriolis Effect

Schematic representation of flow around a low-pressure area in the Northern hemisphere. The pressure-gradient force is represented by blue arrows, the Coriolis acceleration (always perpendicular to the velocity) by red arrows

I was reading the article on the coriolis effect, which featured the following illustration. This diagram shows that air travelling in an East-West or a West-East direction will be deflected perpendicular to their velocity. How is this possible, considering that they are travelling along the rotation of the earth? —Preceding unsigned comment added by 76.68.246.134 (talk) 18:05, 24 February 2008 (UTC)

Consider that air from all directions except due east or west are affected by the Coriolis effect. The low-pressure area draws in air from the east and west, which will then be forced to travel with the already-circulating air from other directions. --Bowlhover (talk) 06:54, 25 February 2008 (UTC)

The Coriolis effect will act perpendicular to the rotation axis of the Earth. There is a component which is parallel to the surface of the Earth, which is what is shown in the picture and what is talked about in meteorology. There is also a component which is perpendicular to the surface of the Earth, especially in low latitudes, but that is generally ignored because it is insignificant compared to other forces in that direction like gravity. --Spoon! (talk) 22:05, 25 February 2008 (UTC)

That's true but irrelevant. To understand the Coriolis effect on a spherical rotating surface, you have to think in three dimensions. What you have to remember is that any particular point of the surface is always rotating along a circular path parallel to the equator, otherwise called a parallel of latitude. Consequently the Coriolis force is felt in the plane of that path, not the plane of the local part of the surface.

At the equator itself, for example, a "stationary" object is rotating eastward at a bit over 1,000 mph. It therefore feels a certain amount of upward centrifugal force and is a bit lighter than it would be if the Earth was not rotating. If the object is set in motion eastward at 200 mph, its real total speed is now 1,200 mph and the centrifugal force is increased. This increase in centrifugal force is precisely a Coriolis force, and it is upward -- it has to be, because the Coriolis force is in the plane of rotation.

Now consider an object at say 45° north latitude, moving eastward. It also feels a Coriolis force upward -- but not straight up. It's upward parallel to the plane of the equator. In other words, the force acts at a 45° angle to the ground, angled toward the south. This is equivalent to the combination of a force straight up and another force, in this case equal, pointing south. The upward force is not important for an object that follows the ground, but the southward force makes the object deviate to the right. Similarly, an object moving westward will feel a force downward and to the north, and again will move to the right.

(For the southern hemisphere, of course, you reverse "north" and "south" in the last paragraph, and the deviation is to the left.)

--Anonymous, 08:04 UTC, February 25, 2008.

Hold on, that explanation isn't the coriolis effect. The coriolis effect has nothing at all to do with centrifugal force (that's the Eötvös effect)- it's an 'illusion' caused by looking at motion from within a rotating frame of reference. You can't really understand anything Coriolis without the Foucault Pendulum.. read the article and then, if you don't much value your sanity, gaze on the image to the right. It's screwy but completely correct. :D\=< (talk) 10:17, 25 February 2008 (UTC)

No, that is the Coriolis effect. The Eötvös effect is just a term used to describe the component of the Coriolis effect that is perpendicular to the surface of the Earth when we are talking about situations on the surface of the Earth. --Spoon! (talk) 21:53, 25 February 2008 (UTC)

I think :D\=< is right. Isn't the centrifugal force fictitious? And isn't it the coriolis effect, rather than the coriolis force. Finally, would't the effects of the centrifugal force on a latitude of 45 degreed be straight up? —Preceding unsigned comment added by 76.68.246.134 (talk) 00:22, 26 February 2008 (UTC)

Sigh. Look, the centrifugal effect and the Coriolis effect are both fictitious or illusory forces, hence their alternate names "centrifugal force" and "Coriolis force". They both are the result of viewing things from a frame of reference that is rotating. And they both can be analyzed by considering the real motions. I gave an example where this can be done simply: for an object moving along the equator, the Coriolis force is vertical and amounts to the difference between the centrifugal force on the object as it is and as it would be if it was fixed to the Earth. Think about it. And the answer to 76's last question is no. The fictitious forces depend only on which way things are moving -- not which way is up. --Anonymous, 05:25 UTC, February 26, 2008.

Thanks for correcting me, everyone. I must say I've never heard of the way centrifugal force affects weather systems. --Bowlhover (talk) 05:35, 27 February 2008 (UTC)

Moon and Sun having the same apparent size

The fact that the Moon and the Sun have almost exactly the same apparent size from Earth has always surprised me. Is it really just a coincidence? --Taraborn (talk) 20:22, 24 February 2008 (UTC)

It's variable. Remember you're seeing a halo/glow around the sun. Also, at different times during the day, depending on the relative positions, they will appear as different sizes. One is 93 million miles away, the other is like 240,000. Wisdom89 _{(T / ^C)} 20:29, 24 February 2008 (UTC)

I'm aware of that. Actually, at the age of the dinosaurs, the Moon was quite closer to Earth than it is now. --Taraborn (talk) 18:51, 25 February 2008 (UTC)

But to answer your question, yes, I believe it is just a coincidence. It depends on the sizes of the Moon and Earth and the distances to the Moon and Earth. I don't think that all moons are the same apparent size as the Sun when viewed from the surface of their respective planets. It would be interesting to know if any of them are (although what is meant by the "surface" of the gas giants then becomes a question). StuRat (talk) 20:38, 24 February 2008 (UTC)

As Orbit of the Moon#Tidal evolution of the lunar orbit notes, the radius of the Moon's orbit is (very slowly) increasing (making the Moon appear very slightly smaller) as time goes on. That would imply that the coincidental thing is that their apparent diameters are so similar now, and that in the past the Moon appeared bigger and that in the future it will appear smaller. Unfortunately that article doesn't give figures for the past and future orbits of the Moon, so I don't know how great that change has been, or will be. -- Finlay McWalter | Talk 21:02, 24 February 2008 (UTC)

Considering how briefly humans have been on the Earth compared with the age of the solar system, I'd expect that any change in the apparent size of the Moon was and will continue to be negligible in the period when this size could be seen by humans. StuRat (talk) 21:24, 24 February 2008 (UTC)

It does imply it's just a coincidence though Nil Einne (talk) 09:24, 25 February 2008 (UTC)

It is indeed a coincidence. Indeed, the relationship isn't even dead on. Because the orbits of the Earth and (especially) of the Moon aren't perfectly circular, a solar eclipse will sometimes occur when the Moon's apparent size is appreciably smaller than that of the Sun: an annular eclipse. —Preceding unsigned comment added by TenOfAllTrades (talk • contribs) 21:39, 24 February 2008 (UTC)

On Mars solar eclipses are much less exciting because Mar's moons are so much smaller. Transit of Phobos from Mars APL (talk) 22:11, 24 February 2008 (UTC)

Well Judaism said that the sun was originally a binary star. But the star that became the moon complained "how can you have two kings", and as punishment was reduced in size. But it was also placed a lot closer. So that the far away sun, and the nearby moon both appeared the same size, in memory of what was. Irregardless of what you think of the story, it does show that the ancients knew that the sun was a lot farther than the moon, and that the moon simply reflects the suns light. Ariel. (talk) 12:40, 25 February 2008 (UTC)

Weird Taste and Smell lingering days after taking Advil Cold and Flu

Has anyone ever heard of such a thing? This is the medicine that they now sell only after you show ID thanks to the Patriot Act and anti-bomb and meth lab stuff. So I am wondering if "they" are putting some kind of weird chemical in it now so that people won't want to use it for whatever bad purposes they were using it for. Yesterday it rained here and the air is usually so sweet and fragrant, but instead it smelled, everywhere, like chemicals you put in your pool - not chlorine, but other acrid and ... I cannot ever think of what to compare the smell to...like something you'd preserve dead things in. Lately too food seems a little off, like there is a weird metallic or chemical essence lingering on the fringes of normal flavor. The only thing I can rationally/causally relate it to is the Advil, because I didn't experience it with the nasty cherry-flavored Robitussin cough syrup I swilled for 3 days prior to obtaining the Advil. I only took the Advil on the last day of the sickness. Maybe 3 tablets in all. I feel that if the chemical smell/taste is just coming from *me* sans Advil, then I am as thoroughly pickled in chemicals as was Gloria Ramirez. I am not looking for medical advice, just to see if anyone has heard of similar anecdotes / experiences and knows how long it takes for these chemicals to leave one's body. Thanks. Saudade7 23:58, 24 February 2008 (UTC)

I believe that differences in taste and smell are side effects of some medications. I'd check the label to see if this is a listed side effect for the meds you are taking. StuRat (talk) 01:19, 25 February 2008 (UTC)

That'd be well worth checking out, but it could also be a side-effect of the cold. Infections up there can cause temporary or permanent disruptions to your ability to smell and, therefore, taste. (I really don't enjoy my food the same way in the winter these days.) If it doesn't clear up, consider going to the doctor. Sockatume (talk) 01:58, 25 February 2008 (UTC)

Thanks Sockatume and StuRat, I went out tonight and the rain smelled like...rain! But that smell was so damned weird, truly chemical. It is weird to think how little of a chemical is necessary to wig out all your sense perceptions! I was just wondering if anyone else had experienced this on Advil C&F. love, Saudade7 07:48, 25 February 2008 (UTC)