Paradox: Where is ET?
now think there must be technological life throughout the
galaxy, some perhaps many millions of years ahead of us. They
should already be here. So where are they? This dilemma
is called the Fermi Paradox. Obviously we're missing something.
Here is a compilation of current theories...
Note: This compilation includes both scientific and unscientific
ideas. Also, some of these hypothetical explanations overlap
each other. The correct explanation could be a combination
of several theories. For example, it might well be that technical
civilizations are BOTH rare and short lived.
1: No - or few - other civilizations currently exist
explanation is that the human civilization is alone (or very
nearly so) in the galaxy. Several theories along these lines
have been proposed, explaining why intelligent life might
be either very rare, or very short lived.
No other (or almost no other) civilizations have arisen.
conditions needed for life (or at least complex life) to evolve
are rare or even unique to Earth. Also known as the Rare Earth
It is the nature of intelligent life to destroy itself
civilizations usually destroy themselves before or shortly
after developing radio or spaceflight technology. This theory
does not require the civilization to entirely self-destruct,
only to become non-technological again.
It is the nature of intelligent life to destroy others
species beyond a certain point of technological capability
will destroy other intelligence as it appears, viewing their
expansion as a threat or a kind of plague. Of course, the
first civlization to arise would not have faced this problem
(and that could theoretically be ours).
Life is periodically destroyed by naturally occurring events
Earth, there have been numerous major extinction events that
destroyed the majority of complex species alive at the time.
They can be caused by events such as impacts from large meteorites,
massive volcano eruptions, and cosmic gamma ray bursts. The
extinction of the dinosaurs is the best known example.
Human beings were created alone
is the well-known but unscientific argument which dominated
many religious beliefs for thousands of years: that the universe
was designed for the express purpose of creating humans, and
that it was created by another, much more advanced intelligence
existing before us; for example a god, a cosmic energy or
an alien power of some sort. (cont)