Do extraterrestrials exist?
If they exist, why haven't they contacted us?
I think most reasonable people would say that life probably exists on other planets, extraterrestrial life, obviously. Usually, religious people say that we are alone in the Universe, because the bible does not mention any extraterrestrials. The
odd part is that they often say that the Universe is perfect for
life, while they are also saying that almost 100% of the Universe is
lifeless, this seems a bit contradictory to me.
I
think that wherever there is water (in liquid form), there will be
life, so, we will probably find life in the oceans of Europa, if we ever
go there. The
life there will probably be primitive and not very interesting, at
least not interesting from my point of view, but biologists will be
ecstatic. Anyway, I would not be surprised at all if we find primitive life on other planets. I'm more interested in intelligent life.
How frequent are technological civilizations in the Universe?
There
is the Drake equation, but it has many unknowns, I think a reasonable
number for technological civilizations at any given time is a few per
galaxy, I'd say two or three technological civilizations per galaxy at
any given time. Maybe
there are more or maybe there are fewer, maybe at any given time there
is only one technological civilization per galaxy (statistically), or
even less, like one per two galaxies or even fewer. I don't really know, but there are about 300 billion stars in our galaxy, the Milky Way. There are probably more than 300 billion planets in the galaxy, because one star can have many planets, like our own Sun. Anyway,
if we take that number, 300 billion planets and we ask how many are
good for life, it's a bit difficult to get the answer.
I think that the center of the galaxy is no place for a technological civilization to evolve, but I may be wrong. With that in mind, I'd say that there are about 100 billion planets outside the center of the galaxy. This is a very big number. Even
if we say that there are one in a billion chances for a planet to
sustain intelligent life at any time, we would get 100 planets with
intelligent life. I should remind you that the chances to win at the lottery 6/49 are about one in 14 million for every ticket. To me, it would be incredible if we were the only technological civilization in our galaxy.I
think the main problem is that it takes such a long time for a
technological civilization to arise, 4.5 billion years in our case (the age of the Earth). Anything
could happen during that time, the planet could be utterly
destroyed in the meantime, as it has almost been in its beginnings, when
the Moon was formed.
Civilizations often die, because of diverse causes, sometimes they even destroy themselves. While a civilization is on one planet, it's somewhat easy for it to die. Only
when a civilization expands to other planets, the chances of survival
increase drastically, it's not good to "keep all your eggs in one
basket". So, quite probably, after a civilization has expanded to other planets, it may live for an unlimited amount of time. If
this is correct, as time goes by, there will be more and more
technological civilizations in any galaxy, so, the galaxies should be
full of technological civilizations after a hundred billion years, we
are at the beginning, as it takes billions of years for
the right kind of planets to appear and billions of years for life to
evolve towards a technological civilization, the Universe is only 13.7
billion years old.
How would extraterrestrials look like?
I
think ET would be very different from us, although evolution often
produces the same answer for the same problem, it's called "convergent
evolution" and you can see it in dolphins and sharks or in the wolf and
thylacine (extinct). I
think that most species that create technological civilizations will
have a few things in common, like the ability to grasp things in their
hands or equivalent organs. Also,
fire is very important for technology, so I think that ET will be a
terrestrial animal, it's difficult to discover fire under water.
I
think that ET will usually evolve as a predator, just because predators
are generally more intelligent than their prey, just look at a wolf and
a sheep, you need a better brain to hunt an animal than to eat grass,
just because grass is not trying to escape. Humans
have also evolved as predators, this is why our brains grew so much,
because we needed skills to hunt and make better tools/weapons. This is probably one reason why we are so violent. Species
that create technological civilizations will probably start by being
violent too, but I think that they get to a point where the only choice
is between destroying themselves or becoming civilized, as we are
getting to that point and we will have to make that choice.
Should we fear extraterrestrials?
I don't think we should fear extraterrestrials, just because they have no reason to destroy us. Some people give the example of Europeans and more primitive cultures, where the Europeans destroyed them. Europeans wanted things from those primitives, like gold, land, slaves etc. I don't believe that we have anything that extraterrestrials could want. If
they are able to travel here, they are able to synthesize any metal
they want, they have robots that are far better slaves than we would be.
Plus,
as the people from Planetary Resources said, we could exploit more
platinum from one asteroid than all the platinum that we have ever
exploited from Earth, it would be far easier for them to just exploit
asteroids or a planet like Mercury, which is full of metals.
I
don't believe they would want to colonize our planet, as they could
terraform a planet or they could just build a planet from scratch. We would not pose any threat to them, therefore, there would be no reason for them to be violent with us. One
further reason is that if a species has managed to travel between
stars, it has become civilized, otherwise, it would have destroyed
itself by now.
Why haven't they contacted us?
I
think that the only possible reason why we have not encountered
extraterrestrials is that Einstein was right and the speed of light is
the maximum possible speed. We
have ample proof for that, like the LHC, which uses enormous amounts of
energy to accelerate particles to 99.999999% of the speed of light.
If
we imagine for a moment that a technological civilization is 10
thousand light-years from us (which is very close, by the way, as our
galaxy has a diameter of 100 thousand light-years), it would take them
10 thousand years to reach us if they traveled at the speed of light, thus, I think it's easy to see why they have not visited us yet. Furthermore,
it would take our radio signals 10 thousand years to get there, so, by
the time our radio signals get there, humanity might be long gone, as
the first radio signals have left the Earth about 100 years ago.
Why haven't we received their radio signals?
This is probably the most difficult question about extraterrestrials. There
is the SETI program, which is listening for radio signals coming from
outer space, but we have not yet detected radio signals coming from an
intelligent extraterrestrial source. We
would detect ourselves from a distance of about 155 light-years, if we
were sending signals for as long as that, this is very little. Furthermore,
as technology becomes more advanced, we are leaking fewer and fewer
radio signals into space, so, a more advanced civilization should leak
far fewer radio signals than we do. Yet another problem is that we are searching only one frequency at a time and ET is probably communicating by broadband, which means many frequencies at once. Even if we were in the middle of a conversation between extraterrestrial civilizations, we would not know it.
It may be that our equipment is not sensitive enough, or maybe the extraterrestrials are not using radio waves. I
think that civilizations are sending radio signals into space for a
short period of time, before other (more advanced) technologies replace
them, or maybe they are sending the radio signals directly to the
planet, without them escaping into space. Maybe
they are using lasers for transferring most information, maybe they are
using cables, or maybe they are using something completely different
than what we have. We can only hope that some advanced civilization has sent very strong signals towards us, we may one day detect that.
