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  #821  
Old 20.09.2009, 00:14
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Re: Ask a Scientist

Air gets colder when it expands. When air moves upwards it expands due to less pressure and when it moves downwards it contracts. This is called adiabatic heating or cooling.
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  #822  
Old 20.09.2009, 03:03
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Re: Ask a Scientist

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OK, I just about understand that bit; but it still doesn't seem to explain why the tops of mountains are colder than the valleys. If the cold air sinks, shouldn't the reverse be true. Shouldn't Switzerland have valleys full of snow and mountain top resorts?
If you have a nice, still weather system, then the air at the bottom is heated through compression by the weight of the air above (think how a bile pump gets warm as you use it) and also by warming from the ground, which absorbs sunlight and heats up. When you're higher up, there's less air pressure, so less compressive heating and also less ground at altitude, so less heating that way.

As for ice floating, we're bloody lucky it does, or this planet would be a dead ball of ice and rock. If ice sank, then it would expose more water to freezing conditions and so on until it was all frozen. Ice is also a good thermal insulator and helps to trap the heat of the water below, meaning that even if the whole planet did frost over, there would be enough warmth for critters to carry on for some time.
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  #823  
Old 20.09.2009, 07:18
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Re: Ask a Scientist

At the top of mountains, the blanket of air above is thinner than the bottom. Hence it's colder there.

It's not just ice floating that's necessary to support life, it's the fact that water is most dense at 4°C. Water was most dense just before it froze, then ponds and lakes would freeze from bottom up. It's this anomalous density profile, causd by hydrogen bonds, that prevents ponds easily freezing right through, and allows aquatic creatures to survive cold winters.

( This second point is true. The first, well... )
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  #824  
Old 20.09.2009, 11:44
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Re: Ask a Scientist

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If you have a nice, still weather system, then the air at the bottom is heated through compression by the weight of the air above (think how a bile pump gets warm as you use it) and also by warming from the ground, which absorbs sunlight and heats up. When you're higher up, there's less air pressure, so less compressive heating and also less ground at altitude, so less heating that way.
Having lived on the edge of the moors in the UK, I have some first hand experience of this

The valleys are relatively sheltered but the tops of hills are subject to the prevailing winds, and the wind chill factor comes into play.

wind chill factor calculator

I actually lived a couple of miles above a localised "snow line". The UK doesn't get much snow, but when it came that snow line was visible; snow above it took several days longer to melt above the line than below it.

Oh, there was always some wind where I lived. The prevailing wind came from the west, but when it came from the north east it was time to wack the heating up, light a log fire and stay in. At its worst it could turn the whole house into a fridge inside half an hour.
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  #825  
Old 20.09.2009, 19:40
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Re: Ask a Scientist

The question about why it's colder on mountain tops is harder than it looks & we haven't got there yet IMHO. My research (aka Googling) shows that the atmosphere only gets colder as you go away from the Earth for the first 10km (top of Everest, more or less). This bit, nearest to us, is the troposphere. After that it starts warming up again as you rise further. And one thing is certain - it's effing freezing in outer space (-270°C, roughly). So there is no simple geezer-in-the-pub explanation for the whole temperature profile. More later.
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  #826  
Old 20.09.2009, 20:05
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Re: Ask a Scientist

At first, I thought that I was asking a slightly silly question and there would be a simple answer. I am reassured that it is not a simple answer.

What really got be thinking about it was seeing the snow on the Alps in fierce sunlight and wondering why it wasn't disappearing so fast. I felt that I was melting in the heat and getting sunburnt, yet the snow seems to only thaw slowly.
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  #827  
Old 20.09.2009, 22:10
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Re: Ask a Scientist

As altitude increases, the average temperature decreases to −53°C at about 10km above sea level. Then we hit the tropopause, where the temperature is almost constant for the next 20km.

http://science.jrank.org/pages/614/A...e-profile.html

Snow forms when the air temperature is below freezing. Cold air holds less water vapour than warm air. Thus, air below 0°C is going to be almost completely dry. The vapour is dumped as snow.

So mountains get snow because they are high enough to be in air that drops to or below 0°C.

So why doesn't it melt, despite being exposed to more solar radiation? The answers are the albedo of snow, and that it is a good thermal insulator.

http://www.rcn27.dial.pipex.com/cloudsrus/snow.html

Does that add up?
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  #828  
Old 20.09.2009, 22:29
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Re: Ask a Scientist

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I was under the impression that psychology is biology which is chemistry which is in reality physics which in turn itself is actually mathematics being itself all made up.
I don't think Psychology or Philosophy has anything to do with Physics, Biology, Chemistry etc.

Well, when I was at university they had 8 hours of lectures compared to my 32 hours per week and appeared and admitted that they did b*gger all.
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  #829  
Old 20.09.2009, 22:33
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Re: Ask a Scientist

I think that I have just about got it. Thanks everyone.
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  #830  
Old 20.09.2009, 22:35
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Re: Ask a Scientist

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Well, when I was at university they had 8 hours of lectures compared to my 32 hours per week
What? You mean they had to learn things all by themselves for the other 24 hours, while you had all your stuff spoonfed to you?

I can see why you'd be envious...
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  #831  
Old 20.09.2009, 22:41
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Re: Ask a Scientist

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I think that I have just about got it. Thanks everyone.
My previous answer describes the mechanics behind it (air moving up and down, expanding and contracting).
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  #832  
Old 21.09.2009, 14:00
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Re: Ask a Scientist

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...
(think how a bile pump gets warm as you use it)
...
I did, but I rather wish I hadn't...
.
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  #833  
Old 21.09.2009, 14:09
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Re: Ask a Scientist

this question is for weejeem:

cockroach has 7 penises? how does that work exactly, then?
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  #834  
Old 21.09.2009, 14:46
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Re: Ask a Scientist

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this question is for weejeem:

cockroach has 7 penises? how does that work exactly, then?
It's just their way of upsetting the lobsters...
.
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  #835  
Old 21.09.2009, 21:06
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Re: Ask a Scientist

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I don't think Psychology or Philosophy has anything to do with Physics, Biology, Chemistry etc.
Maybe not yet. From a very simplified, scientific reductionist point of view, mental processes boil down to brain neurons tickling each other across synaptic gaps, and hormones. That's all of physics, chemistry and biology together.

Thoughts and states of mind are mental processes. Psychology is the study of these. Philosophy is thinking about thinking, and thinking about the world. These same thoughts are also founded on the physical mental substrate.

So they depend utterly upon physics, chemistry and biology, insofar as we can use these disciplines to construct testable theories to describe mental processes.

I don't think we'll have mind-reading machines for quite a while, but functional NMR - sorry MRI - is helping map states of mind to areas of the brain.
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  #836  
Old 21.09.2009, 23:03
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Re: Ask a Scientist

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Maybe not yet. From a very simplified, scientific reductionist point of view, mental processes boil down to brain neurons tickling each other across synaptic gaps, and hormones. That's all of physics, chemistry and biology together.

Thoughts and states of mind are mental processes. Psychology is the study of these. Philosophy is thinking about thinking, and thinking about the world. These same thoughts are also founded on the physical mental substrate.

So they depend utterly upon physics, chemistry and biology, insofar as we can use these disciplines to construct testable theories to describe mental processes.

I don't think we'll have mind-reading machines for quite a while, but functional NMR - sorry MRI - is helping map states of mind to areas of the brain.
It's closer than you think. The CIA already use MRI as a superior lie detector & Unilever have used it to find people's true feelings (about shampoo bottles ) without asking them.

Physicists love to think that everything boils down to their subject, but it doesn't. Chemistry can survive quite happily without quarks. Lots of biology can survive quite happily without atoms. A lot of psychology is about understanding mental processes, e.g. Steven Pinker's wonderful books, and does not depend on any other science.

Reductionism is wonderful, but only up to a point.
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  #837  
Old 21.09.2009, 23:11
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Re: Ask a Scientist

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Physicists love to think that everything boils down to their subject, but it doesn't. Chemistry can survive quite happily without quarks. Lots of biology can survive quite happily without atoms. A lot of psychology is about understanding mental processes, e.g. Steven Pinker's wonderful books, and does not depend on any other science.

Reductionism is wonderful, but only up to a point.
Which leads us to the subjects of complexity and emergent behaviour.
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  #838  
Old 22.09.2009, 10:52
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Re: Ask a Scientist

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It's closer than you think. The CIA already use MRI as a superior lie detector & Unilever have used it to find people's true feelings (about shampoo bottles ) without asking them.

Physicists love to think that everything boils down to their subject, but it doesn't. Chemistry can survive quite happily without quarks. Lots of biology can survive quite happily without atoms. A lot of psychology is about understanding mental processes, e.g. Steven Pinker's wonderful books, and does not depend on any other science.

Reductionism is wonderful, but only up to a point.
That was a very neat redefinition of the word "science";
I think you got clean away without anyone spotting it.
.
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  #839  
Old 07.10.2009, 18:56
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Re: Ask a Scientist

Next question... sometimes bunches of flowers come with a little sachet of plant food crystals, or flower life extender, or something. It's great stuff and seems to do the trick. What do those sachets contain, and is it possible to make it (or something similar) at home?
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  #840  
Old 07.10.2009, 19:33
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Re: Ask a Scientist

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Next question... sometimes bunches of flowers come with a little sachet of plant food crystals, or flower life extender, or something. It's great stuff and seems to do the trick. What do those sachets contain, and is it possible to make it (or something similar) at home?
I've no idea what's in the sachets - I'm no scientist - but our local florist shop recommends adding aspirin or a few drops of eau javel (sodium hypochlorite - a kind of bleach) to the water. I haven't tried aspirin but I use eau javel (all the usual supermarkets stock it) and it works wonders - roses last for at least two weeks if you trim the ends of the stalks every few days. I guess bleach kills of bacteria but aspirin????
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