FINDING AND COMMUNICATING WITH SPACE ALIENS - SHOULD YOU CARE?
--------Warren Smith March 2001-------------------------------

There is this notion popular in some corners that some day
we'll discover alien intelligent beings, and talk to them, and
this will be an incredible event which will change the human race 
forever and lead to vast technological advances, etc.

Nauseatingly cute actress Jodie Foster starred in a movie
"Contact" which involved quasi-religious alien-meeting experiences
that made us all want to puke. There have been countless other sci-fi
works of the same ilk.  Truly the required rush to the barf bags has
made Mecca pilgrimages look like Arctic exploration.

Well... I say... bullshit.

Do I think alien intelligent beings exist? Yes...
However, the case is not clear. There are calculations indicating
that even simple life is so incredibly improbable and complex that
it must only have arisen once in the universe (here on Earth).
(E.g. consider the number of bits needed to describe the genomes of
the simplest known life forms.) But: nobody really knows how complicated 
the SIMPLEST life MUST be, so that is nonsense. On the other side there are
calculations indicating life must be common and all over the universe.
But all those calculations are based on multiplying a large number of
factors together, all of whose probabilities are very poorly approximately
known, resulting in enormous possible error-factors in total. In short, 
nobody knows a damn thing on either side of the debate.  

Here is one such silly estimate, which is based on the (questionable, since
based on 1 data point!) assumption that humanity is typical, i.e. we are in 
no way special.  In other words, assume ultra-optimistically that every 
star similar to the sun will spawn 1 intelligent race (same number as Earth) 
which will last for as long as humanity has lasted (30,000 years?)
and persist 3000 years as a technically advanced-enough civilization to hope
to be able to communicate with us. (That's 60X longer than humanity
has so persisted, but I'm trying to be optimistic here.)
Since there seem to be 35 stars within 4 parsecs (13.05 light years) of us
[listed in appendix 4 of W.J.Kaufmann&R.A.Freedman: "Universe" Freeman 1998],
only 2 of which (our sun and Tau Ceti) are fairly sun-like,
assume the density of sun-like stars is .0002 per cubic light year.
Assume all such stars last 10^10 years, so the
probability we happen to be in the magic 3000-year wide 
time-interval is 3*10^(-7). Then: the density of civilizations
we can communicate with is 3*10^(-7)*.0002 = 6*10^(-9) 
per cubic lightyear. That means the nearest such civilization
probably is about 2000 light years away. Oh dear.
That means communicating with them both ways would take 4000 years, longer
than the timespan of their and our entire existences as technically 
advanced-enough civilizations! So it would be impossible to communicate 
with them!  Bummer.  (And I happen to think this calculation was 
very optimistic.)

But, just to make you happy, I'm willing to concede I think the aliens 
are out there, and for the purposes of the present argument let us
say the nearest ones are only 50 lightyears away.

Can we communicate with such aliens if they do exist? Can we meet them?
Sorry, I doubt either will ever happen. 

But: suppose we can communicate with them. Such communication
will be extremely delayed (>50 years each way) and probably 
very expensive per bit. For example, here is a technically feasible 
scheme for communicating with aliens:
Explode a $70,000,000 (this price estimate is based on the fact that,
in 1999 dollars, Pu239 costs about 4.8 million dollars per Kg, and
deuterium about $1200 per Kg) 10-megaton H-bomb in 3 microseconds
at most 1 time per hour in order to send (encoded as
the explosion timings), say, 30 bits per explosion.  
Note, the power output in such an explosion lasting 3 microsec is
about 1.3*10^22 watts. If a giant parabolic mirror somehow were used to
send half that power in 1 direction - alienward in a 1-degree-wide cone -
this power would be effectively increased by a factor of 25000, leading
to an effective power of 3.5*10^26 watts. Meanwhile the sun's luminosity is
4*10^26 watts. In other words, the aliens ought to be able
to see it, if they happened to be looking this way in the necessary
3 uSec-wide timespan with a sufficiently big telescope.
(Actually, about a 10-cm diameter hobby-type telescope should easily
suffice to recieve enough photons per 3 microseconds to get good enough
statistics to perform the required pulse-timing, IF the aliens are
only 50 light years away. The required telescope diameter grows
proportionally to the aliens' distance away from us, though; 
thus at 4000 light years, a giant Mount Palomar size
telescope would be needed.)

Of course, the communication scheme I just suggested is
rather crude. Perhaps it can be improved by a significant
factor in terms of cost per bit.  But anyway it seems pretty clear
that interstellar communication with technology like today's is 
necesssary going to be very expensive. No telescope so far has had
enough resolution to see a planet (even a huge one)
orbiting another star; all detections of such planets have been 
indirect. In principle 1 arcsecond of resolution, which today is
being neared by Earth-based adaptive optics, etc, ought
to be able to distinguish a planet 1 AU away from a star (when at
maximum apparent orbital separation) that is 20 lightyears away - IF
the planet and star were comparably bright (which, sadly, they
wouldn't be). The Hubble space telescope managed to
"for the first time resolve the compact SMC ionized
``blob'' N88A (diameter about 3.5 arcseconds)" according to
a web post by M. Heydari-Malayeri (Observatoire de Paris) and NASA/ESA.
Supposedly Hubble has pixel spacings and resolutions ranging from 
20 down to 1/20 of an arcsecond, depending on the instrument.
Of course you could explode your bombs much further away from the sun 
than 1 AU by sending them out there in rockets, thus enabling much less
powerful bombs if the aliens had enough angular resolution... but
on the other hand it is not so easy to build a multi-mile diameter enormous
mirror capable of beaming H-bomb flashes if you have to build it
on Pluto (!) - as opposed to building it on Earth or nearby
(which already is ultra-difficult) - so any energy reduction
you could garner by transmitting from Pluto might be eliminated
due to your inability to direct your signal well enough from
there. So: any way you look at it, interstellar communication
looks hugely expensive.

So to conclude, any interstellar communication using today's technology
at the receivers would necessarily involve signals which
literally outshined their star, either for some brief time period (as in 
my bomb suggestion) or in some agreed-upon spectral band, or they could be
significantly less intense if they were transmitted from Pluto
not Earth in order to allow angular resolution to play a useful 
role. Either way, the energy requirements and/or cost would be immense.

Fine. Now. Let us do a little thought-experiment. Suppose you got to tell
an alien anything you wanted, at a cost of $2.5 million 1999 dollars
per bit, and they got to know it in 50 years.  (If you want to be
optimistic, just assume the cost per bit is 100 times less than this.)
What could you tell them?

Well, maybe tell them about Einstein's General Relativity theory
of gravity. Einstein was an incredible genius, right? And maybe
it only takes 20 pages to describe GR, which maybe could be compressed 
down to 256 kbits, costing only $640 billion to transmit.
No, not good enough: I believe if Einstein had not been around to 
invent GR, it would have been invented anyhow in 40 years. (Indeed I think
Riemann would have invented it if he'd known about Maxwell eqns and special
relativity.)  So the 50 year delay would have meant the Einsteinless
aliens still would have found GR 10 years before your message reached 
them. No good. Try again. Well it is pretty damn hard to think
of ANY scientific achievement by ANY genius which probably would
not have been invented within 50 years anyway.
OK, how about the human genome - send that to them. Well
the human genome is 6 gigabits. Even if it is 99% "junk DNA",
still it is 60 megabits. That means 150 trillion dollars in transmission 
costs, and a transmission time of 3 million hours, i.e. 342 years.
Sorry, took too long to transmit, and cost too much.
Try again.  OK, how about telling them how to construct
silicon-based Pentium (TM) computers running Microsoft Windows (TM),
surely an amazing technical achievement of humanity?  Well, no,
Microsoft Windows source code and the required description of the
Pentium seems to be at least a comparable number of bits to the human genome...
Can't do it.  You begin to get the picture.  I daresay something
useful could be transmitted, but it is not so easy to think of it, is it?

So in conclusion:
I think alien contact is unlikely, and even if it ever does happen, it
will be a heck of a lot less consequential than is commonly assumed
by starry-eyed sci-fi fans and space freaks. So there.