Thursday, February 18, 2010

Small differences

http://dsc.discovery.com/news/2009/09/18/coldest-moon.html

Coldest Place in Solar System: Our Moon
Seth Borenstein, Associated Press

June 18, 2009 -- Astronomers have found the coldest spot in our solar system and it may be a little close for comfort. It's on our moon, right nearby. NASA's new Lunar Reconnaissance Orbiter is making the first complete temperature map of the moon. It found that at the moon's south pole, it's colder than far away Pluto. The area is inside craters that are permanently shadowed so they never see sun.

"It's sort of like a faint glow and that's your only source of heat," said David Paige, a University of California, Los Angeles, scientist who is part of the NASA team. "Right here in our own backyard are definitely the coldest things we've seen in real measurements."

Temperatures there were measured at 397 degrees below zero. That's just 62 degrees higher than the lowest temperature possible.

Pluto is at least a degree warmer even though it is about 40 times farther away from the sun.

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The earth and moon are the same distance from the sun. The reason the earth is not as cold as the sun is that the earth has greenhouse gases. The gravity on the moon is too weak to hold onto gases. To expect that we can increase the amounts of greenhouse gases w/o it having an effect on our temperatures just doesn't make sense, unless there are enough negative feedback loops to counteract it. Unfortunately, so far we have seen more effects from positive feedback loops than from negative ones.

Eg., when the temperature is warmer, more water evaporates from the oceans, and water is a greenhouse gas, causing additional warming.

The assertion that small differences don't matter is clearly nonsense. Just consider body temperature. A very small addition of body heat, causing a fever, can kill us.
Consider our body temperature in kelvin degrees, in which absolute zero (no heat) is 0K, so that temperature ratios reflect the ratio of the amount heat represented.

To convert kelvin to Fahrenheit: K = (F + 459.67) * 5/9
So 98.6F = 310.15k 105F = 313.71K
313.71 = 310.5 + 310.5*0.0115
So, 105F is only 0.0115 = 1.15% hotter than 98.6F

Biologists and physicists could give many examples of small differences causing large effects.


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