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September 21

GEarth blue streaks

I was playing around with the sky part of Google Earth when I came across these really odd parallel blue streaks. Here's a .kmz link to the location: BlueStreaks.kmz. I was wondering if those are actual astronomical thingamabobs or if they're just a glitch that somehow got into the photo-ing stuff.

For those of you who don't feel like opening the .kmz file, here's a picture of the view: Blue Streaks Foxjwill 02:35, 21 September 2007 (UTC)[reply]

Satellites can leave streaks like that on astronomy pictures- the camera takes three different color snapshots of each section, so things that move really fast (like satellites) only show up in one color and as streaks because of the long exposure time. Galaxyzoo has a good explanation in section 3. Except that there are two parallel lines here, so it might be something else. 68.231.151.161 03:42, 21 September 2007 (UTC)[reply]

Satellites with a complicated cross-section (say, a pair of solar panels) can leave parallel streaks like that. There's a certain lack of scale there, so it could also be something more prosaic, like UFO running lights. --Carnildo 22:36, 21 September 2007 (UTC)[reply]

Hypotheticals in chemistry

I posted this question in talk:sulfonic acid 3 weeks back but got no nibbles, so I thought I'd ask it here...

I can guess—but I cannot find a definitive explanation of—what is meant by calling these babies [the sulfonic acids] hypothetical. I suppose it's OK to use a bit of jargon that's well known in chemistry, but I'd suggest creating an entry for it on the "hypothetical" page because at least one reasonably well educated person (me!) cannot fully understand the first sentence of the article, and that's poor design form in Wikipedia.

PaulTanenbaum 02:42, 21 September 2007 (UTC)[reply]

Ball-and-stick model of methanesulfonic acid

I think what it means is that the sulfonic acid shown on the top does not exist in this form (see tautomer). It would convert to sulfurous acid (bottom) in solution because that would a better bonding configuration for the sulfur. However, if rather than a not very electron donating hydrogen were swapped out for a methyl, butyl, etc. group, the six bonded sulfur configuration found in sulfonic acid would be stable enough to exist. Even if it weren't especially stable, it wouldn't have much choice anyway. Unlike the hydrogen attached to the sulfur, an organic group could not be transposed to an oxygen form a err... sulfonylester? (not sure what to call it) because the intermediate would involve an extremely thermodynamically unfavorable carbocation. Methanesulfonic acid certainly exists. Here is the MSDS. http://physchem.ox.ac.uk/MSDS/ME/methanesulfonic_acid.html Sifaka ^talk 05:04, 21 September 2007 (UTC)[reply]

I'll take a stab: if we consider a zwitterionic resonance form of O=S ↔ O^–1–S⁺¹, then we have an H on a partially-positive S (see sulfoxide for a dramatic example). Tautaumerizing puts it on the O instead (quenches partial negative) and leaves a lone-pair on the S (quenches the partial positive). The protons on the carbon attached to S in an alkylsulfonate are particularly acidic, further support for S being non-stabilized by having a non-electron-donating H attached to it. Interestingly though, if you deprotonate sulfurous acid to get bisulfite, then you do get a structure with H on S. Note that carbocationic rearrangements are quite common but they are more often occurring by concerted migrations instead of a carbocation popping off and then later reattaching somewhere else. And they usually need a pretty strong driving force (a preexisting carbocation, a strained ring, etc). DMacks 06:28, 21 September 2007 (UTC)[reply]

Much clearer explanation than mine DMacks. Thanks, Sifaka ^talk 07:12, 21 September 2007 (UTC)[reply]

building downtown nyc

I heard that south of greenwich st. in nyc there used to be ocean, but it got filled up over the years and reclaimed as land. how can you build skyscrapers on a man-made landfill? Don't you need some strong bedrock to support them? —Preceding unsigned comment added by 12.217.199.246 (talk) 06:12, 21 September 2007 (UTC)[reply]

You drive piles down through the fill into the bedrock, below the water line if that's where the bedrock is. —Tamfang 08:08, 21 September 2007 (UTC)[reply]

What will happen to this molecule?

While answering the question two above I wondered about the stability of this molecule. After querying NIST Chemistry WebBook and google, I couldn't find any examples of anything like this as a functional group. I figure it must spontaneously react with itself. Assuming 2 molecules reacting with one another, I pushed arrows as shown to produce two Organosulfonic acids. Is this a reasonable assumption for what would actually happen? Organic chem buffs, what do you think? Sifaka ^talk 07:07, 21 September 2007 (UTC)[reply]

It is a reasonable explaination of what might happen if you had that radical in a jar...but of course that doesnt mean anything like that will occur :DShniken1 11:59, 21 September 2007 (UTC)[reply]

It's a sulphite ester. In genereal no this reaction won't occur because the R-O bond is much stronger than the R-S bond - so the equilibrium constant would prevent the reaction occuring to any noticeable degree.87.102.87.157 15:01, 21 September 2007 (UTC)[reply]

I don't have experience with the electronics/stability/reactivity of sulfite esters themselves, but in related structures such as DMSO, the sulfur-bound oxygen, not the sulfur itself, often acts as the nucleophile. HSAB is an interesting way of comparing relative stabilities of these structures. Perhaps by choosing an electrophile (Lewis acid, in HSAB terms) that is particularly soft, one could get reaction at the S or migration of something from O to S? Acid hardness is yet another way of explaining the relative stability of sulfonic acid vs sulfurous acid: H⁺ is a hard acid, O^– is a hard base, S^– is a soft base. A bit of caution here: relative stability is about which structure would be preferable, not whether or how one structure could convert to a more stable one…lots of things are "stuck" in less stable forms because there's no viable mechanism for the change. DMacks 16:14, 21 September 2007 (UTC)[reply]

Good point, if R was Br (bromine) I would expect that change, but R often means an alkyl or other hydrocarbon group - I made that assumption.87.102.87.157 17:00, 21 September 2007 (UTC)[reply]

After sitting on it for a night I found what appears to be a more plausible multistep reaction which is sort of analogous to a decarboxylation reaction but forms sulfur dioxide gas and some sort of alcohol depending on what the R group is. The most unstable intermediates are protonated oxygens and oxyanions in neutral reaction conditions although this reaction would be catalyzed by acids or bases. Seems more likely to me. Sifaka ^talk 17:25, 21 September 2007 (UTC)[reply]

Yup, now we're talkin'! Hydrolysis (cf. R migration O→S) is a well-known process among many types of esters. For alkyl sulfates, both the C–O and O–S bonds are labile under various conditions (loss of an intact sulfate or hydrolysis of the ester bond, respectively), though some of the mechanisms are still being investigated (doi:10.1021/ja0279747 S0002-7863(02)07974-X for example). Sulfite haloesters are also highly reactive at the C–O bond (see thionyl chloride#Use in organic chemistry). Then there are also the various sulfite ester hydrolysis mechanisms (see [http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_abst_e?cjc_v77-413_55_ns_nf_cjc Can J Chem. 55 1977 2971-2976). DMacks 17:49, 21 September 2007 (UTC)[reply]

mitosis,meiosis in humans

what takes place in mitosis in the human body? what takes place in gamete formation in humans? —Preceding unsigned comment added by 82.206.143.13 (talk) 07:15, 21 September 2007 (UTC)[reply]

I would suggest reading the articles mitosis and meiosis to answer your question. Sifaka ^talk 07:21, 21 September 2007 (UTC)[reply]

Colourblindness

Are all animals colourblind?124.7.82.159 09:05, 21 September 2007 (UTC)[reply]

I would think it unlikely. It might be a good start to think about why animals, in it's broad sense, are coloured. Off the top of my head I'd say there are three drivers for colour in animals.

Camouflage, defensive and offensive.

Attraction for mating or territorial defence.

Chance, as when the animal has other features that don't require specific colouration, e.g. elephants or rhinos.

Clearly perception of colour is important and thus presumably visible in a wide range of animals, birds (of paradise, for example) lizards and cephalopods are three groups that come immediately to mind where colour is used to transmit information. If it transmitted we must assume it is received. Richard Avery 09:21, 21 September 2007 (UTC)[reply]

See our articles on color vision and monochromacy where this topic is discussed in (a little) more detail.--Shantavira|^{feed me} 11:26, 21 September 2007 (UTC)[reply]

No - most animals aren't colour blind - although that term is a horribly inaccurate one and requires clarification before we can proceed to answer the question.

First let's establish a baseline for comparison. Humans can see only three colours - red, green and blue - and we have other cells in our eyes that detect brightness (without responding to colour) and which are really sensitive to motion. Everything else we see is a mixture of those colours - yellow is a mixture of red and green for example - even 'normal' humans are colour blind in that we are completely unable to distinguish between a mixture of red light and green light (such as is produced by your computer screen when it displays "yellow") and a pure yellow light such as would be found in a rainbow or being emitted by sodium street-lamps. This makes us 'trichromats' - we see everything in terms of three colours plus an overall average 'brightness' value that's mostly useful at night.

People who are "colour blind" are sometimes dichromats with one set of colour detection cells completely missing...or (like my son) they may be trichromats who have weak colour perception in one or more sets of colour detectors making some colours hard to distinguish. Those people don't see things in black and white - they see them in a different range of colours depending on which set of detectors are missing or weak. It's wrong to call such people "colour blind" because they do see colours - but that's the term we use. My son can correctly identify all of the colours in a rainbow - but cannot pass a colour blindness test.

A really unfortunate person might have one or zero colour detectors - and they will truly only see in shades of grey and might truly be called 'blind' to colour.

There are also a very, very few women who are tetrachromats (in fact only one such person has been clearly identified and tested) - they can see colour even better than a typical human...compared to them, we are ALL "colour blind"!

OK - so with those things in mind - how does animal colour perception stack up against us humans:

Some animals (such as owls) need really good vision at night - they don't bother cluttering up their eyes with useless (to them) colour sensors - but instead pack them with brightness/motion detectors. They see in amazingly low light levels - but they are utterly colour-blind. Their eyes are also somewhat sensitive to Infra-red so they can see 'heat' from warm, furry mice...but I believe that's still a monochrome sense. The world for them must be a lot like using military night-vision devices is for us.
Some animals (like dogs and cats) are dichromats by nature. The can see in colour - much like a dichromat human - but not with as much colour sensitivity as a trichromat human. I wouldn't call them 'colour blind' so much as 'colour deficient'. We think that humans probably evolved to see in three colours in order to be able to distinguish red and green so that we could tell the difference between ripe and unripe fruit. Dogs and cats are carnivores - they don't care about that - so dichromaticity is fine for them - and the extra space in their eyeballs allows for better night vision - which is good for a carnivore.
Some animals (such as the goldfish) have as many as seven different colour detectors in their eyes (heptochromats)!! Their world must be just alive with subtle colour because they see colour incredible better than humans. I have no clue why they evolved this ability.
I read a while back about a species of freshwater shrimp which may have even more than seven colour detector types...perhaps as many as twelve!
Bees can see in ultra-violet light - beyond the range of our eyes. Otherwise plain-coloured flowers often have elaborate patterning in the UV part of the spectrum specifically to attract bees. I don't know whether they can see different 'shades' of UV light or not...I suspect not.

So, no - animals aren't all colour blind. Some are, some aren't, some see colour better than us, some worse - some can see light outside of the "visible spectrum" that we can see in. But there isn't a simple distinction between being able to see in colour or not - there are huge ranges of colours that humans cannot distinguish - and some things we think of as 'colours' (like magenta) that aren't true colours at all - but merely an artifact of our (relatively poor compared to goldfish) colour vision.

SteveBaker 14:35, 21 September 2007 (UTC)[reply]

For a really interesting and thorough discussion of colour-blindness with respect to (scientific) presentations, see this link. The website shows what people with different colour deficiencies see. -- Flyguy649 ^talk _contribs 20:02, 21 September 2007 (UTC)[reply]

Have a read of this thread from a couple of months back, WRT to the colour perception in birds too... --Kurt Shaped Box 02:44, 22 September 2007 (UTC)[reply]

photons and gravity

Are photons affected by gravity? According to the article on Newton's (outdated?) law on gravity, the force must be equal to zero since photons have no mass. If so, how do black holes "trap" photons? (I have almost no knowledge of quantum mechanics and similar things). Thanks. --wj32 ^{talk | contribs} 09:57, 21 September 2007 (UTC)[reply]

In general relativity, mass curves spacetime. In this model, straight lines across spacetime are curved near masses. Since photons travel in straight lines, they will also curve. Black holes curve space time so much that a straight line going out from a black hole (or any straight line that enters the event horizon) enters back into the black hole. A photon following this straight line cannot escape. (I am, of course, vastly simplifying here). Capuchin 10:14, 21 September 2007 (UTC)[reply]

You can't use Newton's laws to talk about black holes—the latter are a prediction of General Relativity and have nothing to do with Newton. General Relativity supercedes Newton. --24.147.86.187 13:01, 21 September 2007 (UTC)[reply]

That's not entirely true. Somewhere between the periods of "Newton develops theory of gravitation" and "Scientists decide the particle theory of light doesn't work too well", someone pointed out that if light were subject to gravity - and there was no actual reason at the time to suggest that it wouldn't be, even if it were some strange kind of effectively massless particle - then it would be possible to have an object of such a size and mass that its escape velocity would exceed the speed of light, hence creating a black hole. Confusing Manifestation 13:38, 21 September 2007 (UTC)[reply]

Indeed. John Michell predicted the existence of black holes in a letter to Henry Cavendish in 1783. The text of the letter is here - the part dealing with black holes is paragraph 16. Gandalf61 13:48, 21 September 2007 (UTC)[reply]

So an idea based on a misunderstanding of gravity and a misunderstanding of light counts as a prediction of something rooted in different conceptions of both? Not in my book. --24.147.86.187 00:35, 22 September 2007 (UTC)[reply]

Depends on what it means to know/predict something. Someguy1221 00:47, 22 September 2007 (UTC)[reply]

Certainly photons are bent by gravity - check out Gravitational lens - in which the bending of light by the gravitational field of some large body out in space is used to magnify the image of more distant objects in exactly the same way that light is bent by a glass lens. There is a photo there showing it actually happening - so it's hard to deny! SteveBaker 16:52, 21 September 2007 (UTC)[reply]

And you don't even need something as massive as a black hole to visibly bend the path of a photon. Light curving around extrasolar planets has been used to discover them. See gravitational lensing. --Sean 17:05, 21 September 2007 (UTC)[reply]

The odds of having a planet lens some distant object is really small - as our article points out, it's only been recorded once - and the alignment was too brief for anyone to double-check it. Large objects like galaxies and black holes bend light by so much that a chance alignment is not really needed - so while it's true that you can do this with planets, it's much easier to demonstrate with bigger objects. SteveBaker 17:24, 21 September 2007 (UTC)[reply]

Gravitational microlensing had found three planets as of this two-year-old paper. --Sean 20:00, 21 September 2007 (UTC)[reply]

I don't really buy that photons have no mass. Experimentally, all they could determine is that they have no mass above a certain threshold which they can measure. But, let's say they are right and photons have no "mass". That really means photons have no rest mass, which is a useless bit of data since photons are never at rest. They do have relativistic mass, however, when moving (which is always), that explains why they are pulled by gravity and why they can exert a pressure on a solar sail. (This may not be the current way of stating things, but I find it useful in explaining photon behavior under Newtonian mechanics.) StuRat 15:43, 22 September 2007 (UTC)[reply]

Forgive my Newtonian blundering, but they seem to have a distinct lack of kinetic energy. Plasticup ^T/C 20:42, 23 September 2007 (UTC)[reply]

On the contrary -- all of their energy is kinetic.

I think the general rule is, if you naively calculate what will happen to photons in a gravitational field by computing their "mass" as their energy divided by c² and working from there, you will get within a factor of two. For some calculations it's almost exactly a a factor of two; there's probably some deep reason for this but I don't know what it is. --Trovatore 20:48, 23 September 2007 (UTC)[reply]

Physics

So this is sort of a bullshit question. As it seems mathematically simple. The question goes something like this: An automobile starts from rest and accelerates to a final velocity in two stages along a straight road. Each stage occupies the same amount of time. In stage 1, the magnitude of the car's acceleration is 3 m/s². The magnitude of the car's velocity at the end of stage 2 is 2.5 times greater than it is at the end of stage 1. Find the magnitude of the acceleration in stage 2.

a1 = v1/t1 (that's obvioius)

a2 = v2/t2 (obvious as well)

v2 = 2.5v1 (seems obvious)

t1=t2 (probably the most obvious)

So given that a1 = v1/t1....v2 = 2.5v1, one can say that a2 = 2.5v1/t1

Since v1/t1 = 3m/s². Now one could play with equations and get a2 = 2.5 (3m/s²) = 7.5 m/s²

However, this is stated as being wrong. Either I made a complete mistake or something else is up. Anyone know what? Thanks HERODOTUS 14:22, 21 September 2007 (UTC)[reply]

Your second equation should be a2 = (v2-v1)/t2, and thus a2 = (1.5)v1/t1. Gandalf61 14:39, 21 September 2007 (UTC)[reply]

Oh there we go... forgot about getting the change in v. thanks. HERODOTUS 14:45, 21 September 2007 (UTC)[reply]

Sky and Planet Earth

What makes the sky and our planet appear blue from outer space?24.91.219.166 14:59, 21 September 2007 (UTC)[reply]

Water molecules in the atmosphere refract ("scatter") blue light more than other colors, due to the wavelengths involved. Similar to how a prism refracts a beam of light into a rainbow - some colors are "bent" more than others. Saturn 5 15:35, 21 September 2007 (UTC)[reply]

See Diffuse sky radiation. DMacks 16:19, 21 September 2007 (UTC)[reply]

See Mie scattering and ~~Raleigh~~ Rayleigh scattering. SteveBaker 16:40, 21 September 2007 (UTC)[reply]

Yeah. "Raleigh scattering" is what Hurricaines fans do after the game. DMacks 17:23, 21 September 2007 (UTC)[reply]

And the oceans appear blue from above because they reflect blue sky; without atmosphere I guess they'd look muddy green. —Tamfang 19:24, 21 September 2007 (UTC)[reply]

No, water is actually blue. It's very faint though, which is why you have to look through a lot of it to really notice. Someguy1221 22:22, 21 September 2007 (UTC)[reply]

If you want proof, go to Crater Lake sometime. It's incredibly pure water a few thousand feet deep -- and incredibly blue. The pictures in the article don't do it justice. --Carnildo 22:41, 21 September 2007 (UTC)[reply]

Air appears to be slightly blue also - when I looked at the dome of a nuclear reactor from a long distance away it was pale blue, as I walked towards it the colour changes to bright white. 80.0.114.206 13:52, 22 September 2007 (UTC)[reply]

INCORPORATION OF INTERMEDIATE FREQUENCY

DEAR SIR. I AM LIAQUAT JAWED FROM KARACHI PAKISTAN. SINCE LAST FIFTEEN DAYS I AM IN A SEVIER CONFUSION THAT AS GIVEN BELOW;

1) WHAT ARE THE BASIC RANGES OF INTERMEDIATE FREQUENCIES FURTHER THAT VHF/UHF DOES COME UNDER THE RANGES OF INTERMEDIATE FREQUENCIES .

2) WHETHER CATV DISTRIBUTION AMPLIFIER OR CATV LINE AMPLIFIERS DO INCORPOATE THE INTERMEIDATE FREQUENCY.

3) WHETHER CAN WE CLASSIFY THE CATV DISTRIBUTION AMPLIFIERS OR CATV LINE AMPLIFIERS UNDER THE CATEGORY OF INTERMEIDATE FREQUENCY INCORPORATING AMPLIFIERS.

WAITING FOR YOUR AN EARLY REPLY.

THANKS AND BEST REGARDS.

LIAQUAT JAWED —Preceding unsigned comment added by Lachi9 (talk • contribs) 16:12, 21 September 2007 (UTC)[reply]

Ow! Please type in mixed upper and lower case in future - typing in ALL CAPITALS seems rude to most people. SteveBaker 16:37, 21 September 2007 (UTC)[reply]

I suggest you start by studying our articles on radio frequency and CATV. (I'm not sure what you mean by "intermediate frequency").--Shantavira|^{feed me} 18:30, 21 September 2007 (UTC)[reply]

We have an article on intermediate frequency - but it doesn't list the UHF and VHF IF's. SteveBaker 20:03, 21 September 2007 (UTC)[reply]

For CATV applications in North America, I think the intermediate frequency band is 41 – 47 MHz. --71.175.68.224 15:17, 23 September 2007 (UTC)[reply]

fish in water

take a bucket of water full to the brim(water about to overflow) add a fish any type dead or alive,no water will become displaced why is this? —Preceding unsigned comment added by 83.71.37.244 (talk) 18:07, 21 September 2007 (UTC)[reply]

Because what you just stated doesn't happen. Water is displaced. If you put something very small in a very large container of water, it is possible for surface tension of the water to bulge upward without overflow - but the bulge is still displaced water. -- kainaw™ 18:09, 21 September 2007 (UTC)[reply]

See meniscus for a little more info. That article could do with some more info, but that is the phenomenon you would observe. Saturn 5 18:12, 21 September 2007 (UTC)[reply]

If you toss a fish into a bucket of water then the water level goes up. If it's "full" beforehand then it overflows (if there was room for a little more water because of meniscus effects then the bucket wasn't full yet). The questioner is incorrect. Is this some kind of urban legend you read someplace? SteveBaker 20:02, 21 September 2007 (UTC)[reply]

If you toss a struggling live fish (or a dead fish from a sufficient height) into a bucket, it may splash it's own volume of water out of the bucket, in which case the waterline on the bucket would remain the same. StuRat 15:27, 22 September 2007 (UTC)[reply]

Unless the fish dissolves in the water, it will cause the bucket to overflow (or form a meniscus). If you put salt in a full bucket of water, this will not happen, because the density changes (instead of the volume). Nimur 18:02, 22 September 2007 (UTC)[reply]

Sleepless early-hours mulling over past bad events

It seems common for many people to involuntarily mull over past bad events if they are sleepness and half-awake in the early hours of the morning. Does anyone know why there is a psychological tendency for humans to do this? Or how to stop it? Thanks. 80.2.199.116 20:05, 21 September 2007 (UTC)[reply]

See cognitive behavioral therapy for the field of techniques on controlling negative thoughts. --Sean 22:05, 21 September 2007 (UTC)[reply]

To stop it, you refute those thoughts and think of something pleasant/interesting to you. Alternatively, you can refuse to accept any words in your thoughts, only pictures. Eventually the pictures will fade and you will lose consciousness. —Preceding unsigned comment added by 88.110.12.8 (talk) 02:21, 22 September 2007 (UTC)[reply]

Useful advice, but why do humans suffer this in the first place? 80.0.131.244 08:53, 22 September 2007 (UTC)[reply]

Very shortly and simply put: our defense mechanisms are not as strong during the night as they are during the day, so unpleasant thoughts have a stronger impact on us. Lova Falk 09:14, 22 September 2007 (UTC)[reply]

One theory of sleep is that the brain uses this opportunity to review past events, consider where mistakes were made, and formulate a plan on how to do things better in the future. A semi-sleep state may take on some of these characteristics, too. StuRat 15:24, 22 September 2007 (UTC)[reply]

how old is stone bone

Many years ago i found a petrified bone in the bad lands of South Dakota, it appears to be a femar of a four legged animal. The bone has become brittle stone. The bone marrow has become crystalized. Any idea how long it would take for that to happen? Hundreds, thousands, or millions of years? —Preceding unsigned comment added by 69.254.44.75 (talk) 20:20, 21 September 2007 (UTC)[reply]

If it's still bone, it's probably not too old, as actual preserved tissue from the distant past is extremely rare. If it's stone, it could be anywhere from thousands to hundreds of millions of years old. See fossils. --Sean 22:09, 21 September 2007 (UTC)[reply]

I'd take it to a natural history museum and ask them to tell you what it is. It's probably just a 1000 year old wolf or something similarly worthless, but you never know, it may be some type of dinosaur bone. (Make sure you obtained it legally, though, as some areas, like National Parks, don't let you take fossils home.) Also, how big is it ? (A 10 foot long femur would definitely make it a dino bone.) StuRat 15:15, 22 September 2007 (UTC)[reply]

Hmm the article on Mineralisation is incredibly weak, so no help there! —Preceding unsigned comment added by 88.109.137.161 (talk) 01:16, 23 September 2007 (UTC)[reply]

As already said, it's most likely modern. If not, and if it is from some legal area in the White River Badlands, it is likely Oligocene in age, more or less, 25 or so million years. Cheers Geologyguy 01:35, 24 September 2007 (UTC)[reply]

Any Aussies here?...

I was just at a local bar. We were 'discussing' fall/autumn. Some were saying that TODAY, September 21st was the first day of fall. I said, "No. The official date of fall this year is Sunday, September 23rd." Ok, that`s not a question. One of the patrons said that he lived for several years in Australia, here`s the "Aussie" connection, and that THEY 'celebrate' the changing of the seasons ALWAYS on the 1st of the month of the 'official' change. Of course, they would have 'celebrated' spring, and not fall, but the question is this: Is it true, that they, the Australians, celebrate these 'changes' at the first of their respective months? Seems quite strange to me. Sorry for posting here on the science desk but, I was already 'here', and it DOES have an Astronomy bent! Thanks Dave. 64.230.233.222 21:32, 21 September 2007 (UTC)[reply]

The four seasons are more relevant in the southern part of Australia than the northern part. Here in Melbourne:

Summer is Dec, Jan, Feb

Autumn is Mar,Apr,May

Winter is Jun,Jul,Aug

Spring is Sep,Oct,Nov

I'm not sure what you mean by "They celebrate the changing of the seasons" as I certainly do not celebrate the changing of the seasons nor do I know of anyone who does. However the snow bunnies do celebrate the starting of the ski season but not everyone is a snow bunny. 210.49.155.132 22:59, 21 September 2007 (UTC)[reply]

Thanks for the reply, umm, 210. To simplify, the aforementioned patron, who spent some time in Australia, said that Australians consider the 1st of the month, 'their' official start of a particular season, be it fall or spring or whatever, rather than the equinoxes and solstices as the official beginnings of said seasons. No REAL celebrating implied. Perhaps I should have utilized the term 'observe', rather than 'celebrate'. Is that TRUE? Sorry for any misunderstanding, and ty again. Dave 64.230.233.222 23:19, 21 September 2007 (UTC)[reply]

So you might have heard that the summer solstice (roughly speaking the "longest day of the year", even if it isn't always exactly) used to be called "midsummer", whereas in North America we think of it as the first day of summer. The reason is that average daily temperature somewhat lags the length of the day (it takes a while for the ground and the oceans to heat up), so the hottest three months of the year are roughly the ones between the summer solstice and the autumnal equinox. That makes the summer solstice a convenient marker for the start of summer.

As I understand it, in Australia, for whatever reason, the lag time is a bit less, and they find it convenient to use the first day of the month in which the solstices and equinoxes appear. --Trovatore 00:46, 22 September 2007 (UTC)[reply]

I'm in Sydney, and we change seasons on the first day of the respective month, in fact until a few minutes ago I used to think the entire world changed seasons on the first day of the month... As for the lag time of temperature changes and what not, I think the reason we change on the first day is simply because it is easier to remember, given that often the weather does not match the season I'd say the lag times etc are not taken into account. Still that's just my opinion 124.183.147.134 01:24, 22 September 2007 (UTC)[reply]

Thanks for the replies folks. And 'Sydney', 124; You`re probably just as surprized to hear that the whole world doesn`t change on the 1st of the respective months as I am to hear that you, in fact, DO change at those times. As I said earlier, seems strange to me. Just as an aside, for the Aussies: What do your calendars say? Is your first day of spring actually written on your calendars as occuring on September 1st? Thanks again all. Dave 64.230.233.222 04:27, 22 September 2007 (UTC)[reply]

When it's written on the calendars, yes. However, given that often we get calendars that are actually sourced from overseas, most often produced for the mass market in the US, we will actually find out that September 23 for example is the first day of Autumn (or even worse, Fall), when we're actually three weeks into Spring; d'oh! BTW, I don't mean to enter into a 'your culture is stranger than ours debate', but it always strikes me that starting the season on the first of the month is far simpler - you started this post saying you had a debate about which day was the start of Fall; you never get that debate in Australia as everyone knows it's the first of the month, the only trick can be knowing which month. Cheers, --jjron 12:50, 22 September 2007 (UTC)[reply]

Well, except months are arbitrary, fixed by human convention; solstices and equinoxes are not. Aligning our seasons to the solstices and equinoxes makes it look like the seasons aren't arbitrary either. Of course it's really just a trick. If we wanted summer to be the fourth of the year with maximum insolation, it would run from early May to early August (or, I suppose, early November to early February for y'all). --Trovatore 17:15, 22 September 2007 (UTC)[reply]

Hahaha. Good replies folks. Thanks to all for your insigthful inputs. Trying to enjoy MY 'last' full-day-of summer here. CHEERS! Dave 64.230.233.222 21:26, 22 September 2007 (UTC)[reply]

I think it is important to note one unimportant seasons are in Australia compared to other countries (at least in the north).. School/University terms/semisters in the northern hemisphere is centred around the seasons. You start mid yearat, after "summer", as I understand it. Here in Aus we start at the start of the year, and we dont really consider it starting after the summer break, it is more of the christmas break, this goes for work places as well. It appears to me that the seasons play a much more central role in the daily lives of you northerners so you pay more attention to when each season starts. Also remember there are no (native) desicuous trees in Australia so leaves do not fall off trees in autumn..Shniken1 01:34, 23 September 2007 (UTC)[reply]

The culprit for fiddling with the date for the change of seasons in Australia was the original governor of the penal colony in 1788 who, after listening to complaints from his garrison troops of the New South Wales Corps that their winter uniforms were too hot for September decreed that henceforth winter would end at the 31st. August. The other seasons then had also to fall into line. Greetings from Oz. —Preceding unsigned comment added by Vorc (talk • contribs) 07:04, 24 September 2007 (UTC)[reply]

The start of each season (start of the month) has always been commented on by my family and friends. Often the weather people on TV mention how much rain the past season has had compared to average. More "observed" than celebrated.Polypipe Wrangler 00:44, 25 September 2007 (UTC)[reply]

Number of neurons in the human brain

What is an estimate of the number of neurons in the human brain? Please cite a research source.72.75.96.28 21:30, 21 September 2007 (UTC)superiorolive[reply]

Neurons#Neurons_in_the_brain: "One estimate puts the human brain at about 100 billion (10¹¹) neurons and 100 trillion (10¹⁴) synapses." This review says "Estimates for the human brain range between 10 billion and 1 trillion. The imprecision in these estimates is due almost entirely to uncertainty about the number of granule cells in the cerebellum, a problem that can be traced back to a study by Braitenberg & Atwood (1958). More recent work by Lange (1975) makes a reasonably accurate estimate possible: The average human brain (1350 gm) contains about 85 billion neurons. Of these, 12 to 15 billion are telencephalic neurons (Shariff 1953), 70 billion are cerebellar granule cells (Lange 1975), and fewer than 1 billion are brainstem and spinal neurons." Rockpocket 21:52, 21 September 2007 (UTC)[reply]

Thank you for this72.75.96.28 02:21, 22 September 2007 (UTC)superiorolive[reply]

Is there any way to stop melanin production in humans?

Is there any way to stop melanin production in humans? And please dont say death or aging or idk. —Preceding unsigned comment added by 81.99.218.58 (talk) 22:28, 21 September 2007 (UTC)[reply]

There are chemicals that will permanently depigment human skin. Or so Vitiligo#Treatment would have you believe. Vitiligo, by the way, is a natural condition in which the body has no ability to produce melanin over patches of skin. Someguy1221 22:32, 21 September 2007 (UTC)[reply]

Albinism Cyta 10:22, 24 September 2007 (UTC)[reply]