A little over
half a century ago, saw the beginning of project Ozma (named for the princess
ruling the fictional country of Oz), which continued with the SETI program (Search for ExtraTerrestrial Intelligence).
Assuming that there must be many cases of extraterrestrial intelligence, most
of which will undoubtedly have reached a technology capable of communicating by means of electromagnetic waves,
surely some of them are sending messages that perhaps we can detect and answer.
Initially it was thought that we could take the initiative, sending messages to
stars that might harbor planets with life similar to ours, but this was soon considered
too expensive, so all efforts were allotted to intercept messages, not
necessarily addressed to us. After half a century of efforts, nothing has been achieved.
There have been a few false alarms, but none that has been confirmed.
In a
previous article I mentioned the Fermi paradox, which holds that we must be
alone in the galaxy, because otherwise any extraterrestrial intelligence with several
million years advantage would by now be here, because it would not take long to
colonize the whole galaxy, even at the interstellar speeds we will reach in the
next few centuries.
- They are not here because we are the first.
- They are not here because all previous
extraterrestrial intelligences have self-destructed before colonizing the galaxy.
- They are not here because, although there are extraterrestrial
intelligences, none has wished to colonize the galaxy.
- They are here, but we have not noticed
them (this
is what proponents of the UFO phenomenon say).
In 2002, in
his book Where Is Everybody? Stephen Webb tried to collect the
largest possible number of responses to the Fermi paradox, including some
hilariously absurd, such as they are here
and they call themselves Hungarians. His solutions are grouped
into three groups, approximately equivalent to those listed above:
- They do not exist: 19 solutions, which reduce to the
first two previous explanations.
- They exist, but still have not come this
far, nor contacted us: 22 solutions, including those which reduce to the third case above, plus
a few more trying to explain our failure to detect their communications.
- They are here: 8 solutions equivalent to the
fourth listed above. One of them, by the way, God
exists (and therefore there is extraterrestrial life − God)
is clearly absurd, because it makes necessary to redefine what is meant by
extraterrestrial
life.
To these 49
solutions, the author adds number 50, his favorite. In fact, this solution does
not solve the paradox, although it tries to explain why we have not received
communications: perhaps there are extraterrestrial intelligences trying to
communicate with us, but either we do not know which device they are using, or,
if they use electromagnetic waves, they use a frequency we have not yet tried, or
we have not listened long enough and must keep trying for a couple of
centuries.
In his book
The Eerie Silence, published in 2011, whose
title I have used in this post, the physicist Paul Davies proposes a solution
different from the previous ones:
If there are extraterrestrial
civilizations, they should be much more advanced than ours. All of them must have
reached the point where artificial intelligence (intelligent machines, robots)
have surpassed and supplanted their creators. These machines will also have achieved
independence from the planets revolving around stars at a convenient distance, and
thus will have overrun the many wandering planets travelling through
interstellar space. As they are superior beings, these robots are not
interested in communicating with us, a lower form of life. This would explain their
eerie absence and their lack of interest in colonizing our planet.
Frank
Drake, who inspired project Ozma and created the famous formula that bears his
name, to calculate the probability of the existence of extraterrestrial
intelligence, estimated in a million the number of civilizations in our galaxy.
More skeptical, or more scientific, the XVII General Assembly of the
International Astronomical Union stated that this number may be anywhere between
one (us) and a billion. In one of my popular science books (Life on other
worlds, 1993) I expressed our ignorance in a different way:
The probability of the existence
of extraterrestrial intelligence is 50%. As we know nothing, this is equivalent
to throwing a coin, and if it comes up heads, we say that we are alone; if tails,
that we have company.
Drake's formula |
Manuel Alfonseca
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