Posts tagged ‘life’

July 18, 2011

What is life? (and why the answer doesn’t matter)

by Nathaniel Virgo

What is life?  Some people will say it’s obvious: life is reproduction.  But I may never choose to reproduce, and a worker ant couldn’t if it wanted to – does that make us dead?

Others will say life is evolution.  But on closer inspection, that doesn’t really stand up either.  Evolution is easy enough to implement on a computer.  You just store a bunch of random bit strings in memory, evaluate them according to some “fitness function”, and then “mutate” and “recombine” the best ones to produce a new generation.  By iterating this process you get what’s called a “genetic algorithm”, and this can be used to design robot controllers and all sorts of other things.  These things evolve, but are they alive?  Some might say yes, but anyone with any experience in genetic algorithms will say no.

June 22, 2011

Fisher on Thermodynamics and Evolution

by Lucas Wilkins

I’ve been reading Ronald Fishers book: The Genetical Theory of Natural Selection, which is now publicly available. I was a little surprised to find he wrote a page or two on thermodynamics and entropy in evolution, here it is, verbatim, with a couple of comments on the numbered points. First though, his definition, in words, of the fundamental theorum of Natural Selection:

The rate of increase in fitness of any organism at any time is equal to its genetic variance at that time.

with that in mind…

May 9, 2011

Is the second law of thermodynamics connected to the expansion of the universe?

by Nathaniel Virgo

This is just a bit of idle wondering, another little bit of amateur cosmology from someone who should probably know better. The question I’m asking myself today is, is the second law of thermodynamics connected to the expansion of the universe?

March 26, 2011

The greatest story ever told (well the first anyway)

by Joshaniel Cooper

Let me prefix this by saying that the early universe was a very boring place. There was a lot of energy, (at one point too much to even allow the formation of matter)  and everything was very ordered with no interesting features. The proof of this comes from the recently measured cosmic microwave background radiation which found that at the point it was created (about 370 000 years after the big bang). The differences in temperature between any points in the universe were around one part in 100 000 (i.e. if it was 100 000K then the max temperature difference would be 1K). A rough idea of the second law of thermodynamics would also make this clear that it is required – if everything gets less ordered with time (entropy increases) then the start of the universe must have been a very well ordered place.


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