Reflection (a1)

Link: http://www.astrobio.net/exclusive/344/defining-life

New information

Scrapped definitions of life

Erwin Shrodinger, 1944: “living matter avoids the decay into equilibrium.”

  • refers to the Second Law of Thermodynamics which says entropy (the spreading out of energy towards a state of uniformity) always increases.
  •  E.g. a cold glass of water gets warmer until it reaches room temperature
  • Living things can resist entropy by metabolism (taking in nutrients and expelling waste byproducts)

Insufficient: Martian soil has a unique soil chemistry that can produce a metabolic-like reaction

“Life is dependent on water”

Insufficient: On earth, life has been able to adapt to the harshest environments, so it is possible that life may have found a way to survive on worlds that have no liquid water.

Gerald Joyce: Life is “a self-sustaining system capable of Darwinian evolution.”

Insufficient:

  • Most life forms are technically not self-sustaining. E.g. Herbivores feed on plants to obtain energy
  • Darwinian evolution needs a huge time scale to be proven

Possible?

Benton Clark: “Life reproduces [and uses energy]. These functions follow a set of instructions embedded within the organism.”

  • Every spontaneous chemical process must expend energy. But they follow the laws of physics –> behave the same every time
  • But organisms have a genetic code, which lets them mutate
  • Reproduction and energy use does not have to occur for something to exist (e.g. only the queen bee reproduces)

What’s interesting: The question whether life can actually be defined

Definition of life now: See reflection a5

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