The question is not
"Why would we want
to find evidence
of extraterrestrial intelligence?"; for most of us the answer to
that question is so obvious it's not worth asking. If someone's
talking to us, we'd like to know!
Rather, it's "Why do we think it's possible
to find evidence of
extraterrestrial intelligence?". After all, if it's impossible on
the face of it, then there's no point in doing it.
With current technology, we won't be able to detect any other
civilization unless they're intentionally sending signals our
way. Random radio noise wouldn't be loud or coherent
enough. So, we won't find ET unless ET wants to be found.
Does it make sense to even bother to search in such a situation?
Would You Rather Ask, "What is SETI?"
The Search for Extra-Terrestrial Intelligence. Check out
these links if you are curious:
The SETI Institute
Now let's get back to the "why" question.
But First ... Does ET exist?
The only honest answer at this time is "We don't know".
one might think that any reasonable model of the cosmos would lead to
the conclusion that it's teeming with life. For, suppose
otherwise ... suppose, in particular, that there's just one
planet with intelligent life in the entire universe. There are
something like 1027
stars in the universe. If just one
has intelligent life, then we must conclude that such life is incredibly
unlikely ... but it is obviously possible. In other words,
it's just barely
possible, and it has happened, exactly
once. Intuition rebels. The universe can't be so finely
balanced as that; if it's possible at all, and there are 1027
stars, it seems like it must
have happened many times.
The notion that it could have happened exactly once
Sadly, there are cosmological models which make the notion that life
might have arisen exactly once
in our cosmos seem far more
reasonable. In brief, suppose that, as Arthur Clarke put it many
years ago, universes float like bubbles in the stream of time ... or in
the Higgs field, or in a Superverse filled with perpetual inflation, or
what have you. Modern theories of cosmology include the notion
that there are many, many universes; perhaps there are an infinite
number. The natural laws may be different
universe. If we assume for the moment that in most
these universes life is impossible, and that only in a relative few is
the balance right for life to form, then we are led to a distressing
possibility: It may be that in most
universes where life
is possible, it is barely
possible. One consequence may be
that, if we plot the percentage of all universes against the number of
life-bearing planets in each one, we find that as we increase the
number of life-bearing planets in each universe, the number of
universes which contain so many living worlds decreases rapidly.
We don't know the shapes of any of the curves, but it seems quite
plausible that, when one sums all the universes with various "life
levels", one could find that most living worlds are in universes which
contain just one life-bearing planet!
But again, we don't know. We can imagine a universe in which life
is common; we can imagine a "multiverse" in which lonely living planets
in otherwise lifeless universes are the most likely
scenario. Speculation won't answer this. The only way
to tell what kind of universe we're in is to look for ET, and find out.
If ET Exists, Why Don't We Have Visitors?
Of course, many people think we do
have visitors. But if
we assume there are no aliens in Area 51, and there was really
nothing to "cover up" at Roswell, and we disallow the testimony of
and ignore the opinions of those who think the Earth is hollow, and the
Sun is a solid ball of
ferrite, and the Sun revolves around the
Earth ... then we're left wondering why we don't have visitors.
In this case the simple answer may be the correct one, and in simplest
terms, it can be stated as: C
are large on a scale that's hard to grasp, and the speed of light is a
crawl by comparison. You can't just casually
bop over to see what the neighbors are doing.
Current theory doesn't just fail to provide provide a mechanism for
traveling faster than the speed of light. It actively forbids
both superluminal travel and communication (see, e.g., the CCentipede
tale). If current theory
correct, then interstellar travel is likely to remain forever either
very difficult or impossible. If we assume, reasonably, that the
density of advanced civilizations is not very high in our galaxy, then
we might not expect our nearest neighbors to be closer than a few
hundred light years away. That's a few hundred years of travel
time, best case. Furthermore, they don't even know we're here,
several hundred years ago we were emitting no radiation they could
detect and everything we've emitted more recently hasn't gotten to them
yet -- so why would they be visiting us?
What's worse, traveling close
to the speed of light requires
prodigious amounts of energy. A traveler going close to C
is enormously energetic, and that energy must come from someplace --
it's not free.
One can imagine ways around these problems (that don't violate current
theory) but it's not obvious they could ever really be made to
work. When we combine that fact with the plausible assumption
that there are, at most
, one advanced civilization per several
thousand stars, it's easy to believe that we have no visitors just
because nobody happens to be visiting us. If our nearest
neighbors are 100 light years away, there might very well be 50,000
stars which are closer to them than we are; even if they're touring
nearby stars they may just not have gotten around to coming by our way
Certainly the apparent lack of visitors is not any sort of evidence
that ET doesn't exist.
So Why does ET Want to Talk To Us?
With all this said, let's just assume ET exists and hasn't chosen to
(or can't) physically visit us. Furthermore, ET is so far away
that we can't hold a conversation. Finally, using current
technology, we can only detect signals from ET if they're beamed
at us, so the only way we'll hear anything is if ET really has
something to say to us. Why would ET do that? We'd
need to assume ET is subject to some sort of overpowering urge to
communicate, to think ET even might
spend time beaming signals
to other stars which are so far away they'll never be able to reply to
those signals. Does that make any sense?
Ask a different question.
Why does this web page exist? It's a "send-only" medium --
there's no conversation involved. I can't even tell if
anyone's ever looked at it (unless I check the logs, of course).
Yet I'm writing it anyway, and sending my signal out into the Great
Beyond of the Internet, to be received -- or not -- by strangers I will
never meet. And millions of other people are doing exactly the
same thing. Web pages are signals sent out into the darkness ...
just like ET's signals sent into interstellar space. Web pages
aren't free (they cost time, if nothing else) and for most of us, they
have no payback.
I don't have a good answer to the question of why there are so many web
pages, but it's a fact that they are there. And those web pages
provide an "existence proof" of the kind of urge to
communicate which could drive ET to beam radio signals at every star
within range which was of the right sort to support life.
By listening for signals from other stars, we're really just trying to
connect up to the interstellar Internet.
Page added 8/15/05