"Steve Dufour" <stevejdufour@yahoo.com> wrote in message
news:744cc401.0310231817.2dd47387@posting.google.com...

Good article. I have one question however: Why does it seem to be
assumed that the aliens are so much like us?  -Steve

I can think of three main reasons. First, if these hypothetical alien
lifeforms were so different from us that they couldn't detect our radio
transmissions or recognise them as evidence of intelligence, then we
probably wouldn't be able to communicate with them anyway so there'd be
little point in even trying. While it might be possible to have a lifeform
based on coherant patterns in the plasma vortices of a star's corona, what
are we going to say to them? "Nice weather..."?
Second, there are only a limited number of possible chemical combinations
that could produce molecules sufficiently complex to form biological
organisms, and of these carbon-based structures are by far the most
versatile and stable. It's just about possible to have a biochemistry based
on silicon, but it won't be anywhere near as adaptable. Also, since hydrogen
and oxygen are two of the most common elements in the universe, and react
easily to form water, it's reasonable to suppose that if there is life on
other worlds, it will probably be based on carbon and water chemistry.
Finally, our aliens would have to come from a world that was at least
vaguely Earthlike, in terms of size, temperature and general composition, or
the chemistry of life couldn't happen. Similarly, if our aliens are going to
develop a complex advanced technology they'll require the use of metals, so
they'll have to be living on a world where metals are easily accessible in
the crust, and where the environment permits those metals to be refined and
worked. It's unlikely that intelligent gasbags floating around in the
atmosphere of a Jovian, or even smart octopii living under the ice of a
frozen moon would be able to build radio telescopes and interstellar
spacecraft.

While there's no guarantee that these aliens would look like us, it's
certainly not impossible. There are only so many viable ways to evolve a
tool-using, intelligent, adaptable creature capable of developing advanced
technology, and as we've seen on our own planet, nature likes to repeat
successful designs.
They'd need to have good eyesight, or at least some analogous sense to
percieve the world around them in detail. They'd need to have grasping
apendages capable of both heavy lifting and carrying as well as fine
delicate work. They'd also have to have the capacity for a complex language
capable of transmiting abstract ideas.
Assuming that these creatures evolved in a world that is not totally
dissimilar to our own (see above, and remember just how many different
environments mankind inhabits on just this one planet) it's not beyond the
realms of possiblity that they might look quite like us. Except for being
green and having pointy ears, of course.

Naturally this is all speculation and educated guesswork, but it's kind of
fun to "design" other possible lifeforms. How do you think they'd look?

--
Cliff Smith

"And we'll be saying a big hello to all intelligent life forms everywhere.
And to everyone else out there, the secret is to bang the rocks together,
guys."