From: Dan Minette [mailto:[EMAIL PROTECTED] >>> There is no reason why the entropy of an open system cannot >>>be reduced.as long as the entropy of other systems that are connected to >>>this system rise at least as much as that system falls. So, localized >>>drops in entropy, which appear paradoxical to the casual observer, can be >>>seen to be very compatible with the laws of physics. >> >> I have long found this topic interesting. Does this have any sort of "action at >> a distance" implications. How is the rise of apparent order, in the form of life on >> earth say, balanced by some entropy increase elsewhere. And what form does this >> take. When I mow my lawn, does some distant sun go supernova? A silly example >> perhaps, but how is the presence of life (which does seem rather anti-entropic) >> balanced somewhere else, in another system. How does this other system know >> to become less ordered?
>Becasue they are connected. Penrose has an absolutely brillient and >intuative discussion of this in "The Emperor's New Mind" I confess, I purchased that an an airport, and never finished it. >The sun radiates photons from its surface at ~4000K via blackbody >radiation. They peak around yellow, in the visiable spectrum. The earth >receives these photons as energy in a relatively low entropy form. Its in >(roughly) thermal equilibrium, so it must radiate the same amount of energy >out. But, since it is at, roughly, 300K, it radiates ~10x the number of >photons each of which has ~10% of the energy of the sun's photons. >This is a significant increase in entropy. Plants produce internal lower >entropy states by absorbing the higher energy photons, and using them in >photosynthesis. If you look at the entrophy of the photons that hit the >earth, and compare it to the entropy of those radiated by the earth, you >will see a much larger increase in entropy compared to the decrease of >entropy in the plants. I can see where you are coming from here, but humour me... The earth re-radiating heat is going to happen, regardless of the presence of life or not. The entropy increase is dependent on the temperature differential ? So for life to increase the entropy of the heat that is re-radiated, it needs to increase that temperature differential (and in doing so, build its little low entropy life package, in the plants etc). Thus, life would need to decrease the temperature of the earth, in order to "buy" this entropy margin. But... what is the non-life temperature of earth? Looking at say the moon as an analogue, one could suggest that life actually warms up the earth, not cools it, thus decreasing the entropy of the radiated heat, not increasing it. Or does it... The earth has an atmosphere, due to its gravity, which the moon does not... here it gets complex... look at venus, is it a fair comparison? So, I like your example, but now wonder how we demonstrate that life reduces the earths "native" temperature, cos if it does the opposite, then its perhaps actually reducing the temperature differential between incoming and outgoing light/heat, and thus actually decreasing the entropy of the local system. Without life on earth, the overall entropy of the solar system would then be higher. And then we are back to my original question... how would the lower entropy state of solar systems with life be balanced out? Of course, this all hinges on the effect of life on the earths temperature... upon which I will contemplate. >Fossil fuels are not just an energy source. They are stored low entropy >states. Yes... and in part they are an energy source, because of their low entropy state. One has to love the Universe. And not just cos its the only one we got ! Andrew
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