Detecting alien life forms
Name: Brian S Foster
What would you do to find out if there is any life form on other planets?
If you mean intelligent life, probably the best way would be to listen
for radio messages, since you could do this from very far away. Earth
emits as much radio energy as a small star --- very noticeable. If you
mean just any kind of life it gets harder and you would have to send a
robot or human in a spacecraft to visit. You could then look for the
absorption of reflected light by oxygen molecules in the atmosphere.
Oxygen is such a reactive molecule that it can only stay in the atmosphere
if it is continually replenished by something, such as plants
photosynthesizing. We cannot of course know that other life will build
itself as does life on Earth, out of carbon-containing molecules which are
formed by cracking apart carbon dioxide molecules with light energy
(releasing oxygen). So the only sure way would probably be to land on
the planet and look around. And even then you might well miss something.
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Update: June 2012