5 février 2008
Radu Popa "Defining the living state via understanding early stages in its evolution"
xenobiologyを通して、地球外生命を探り、生命の定義、起源に迫る試み
Introduction to xenobiology （宇宙生物学とは）
● non-earth-centric description of life, origin, early evolution, macroevolution
● no sharp transition between life & non-life
● no one molecule, structure, force-started life
● being alive is independent of any particular composition
● origin of life: both probability & causality involved
● origin of life: placed at intersection between disequilibrium thermodynamics & theory of information
● xenobiology is different from astrobiology
（XBは地球上の物質を基に考える）
Definition of Life
living entities are self-maintained entropy dissipating system
1) energy dissipative self-maintenance
2) adaptive evolution based on genetic system = learning changes in controlling mechanisms
increasing energy dissipation : lot of energy into out
but no genetic memory
cf. digitizing information; remember the change, but not genetics
Origin of life
chance vs. causality
one big step or many small changes?
non-lifeからlifeに至るchanceは、2の800乗分の1。
chanceだけでは考えにくい。
小さな変化だけで生命が誕生するとした場合、時間が足りない。
大きな変化を考えないわけにはいかない。
Causal origin of life
● life drivers:
internal/external
time-asymmetric physical laws (non-random functioning of the Universe), post-Big-Bang
● anthropic principle --> physicist view
● non-random organization of the Universe
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