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RE: 2nd Law of Thermodynamics
On 27 March 1997, Nathan Myhrvold wrote:
> Also, since it is mentioned in the inclusion in the mail, the biosphere
> is NOT entirely powered by the sun. Bacteria, tube worms and other
> creatures that live on the ocean bottom near deep sea vents are powered
> by heat from the earth.
Talking about the second law of thermodynamics, here's a question
from one of its greatest fans:
These bacteria, tube worms etc. on the ocean bottom are powered by heat from
the earth ?
Great, but please tell me, how exactly does this work ? I don't know
how hot it's down there, let's just suppose the temperature is 350 K.
So our little bacterium is surrounded by an environment
of 350 K, but who cares ? The environment offers a great amount of
energy, but this kind of energy has no value because of the second
law of thermodynamics. Everybody familiar with
the concept of exergy and anergy (I hope those terms exist in
English) will know this. The bacterium needs valuable energy
(exergy) for moving, growing, reproduction etc. A source of heat can
only be used for getting such valuable energy if it has a temperature
higher than the environment.
We human beings have the same problem. We live at a temperature of
about 290 K, which means our whole environment is full of thermic energy, which
cannot be used. It only works if something else exists which has a
lower level of temperature. This may be the ultimate solution of my
question, as the organisms could use the difference of temperature
between the hot ground and the cool surrounding ocean, but this still
does not explain how they do it. (Photosynthesis is a completely
different case, as radiation from the sun contains a high percentage
of valuable energy.)
I'm looking forward to any explanations !
Martin Jehle, Dipl.-Ing.(FH)