Yesterday I picked up this incredible book titled “First Contact: The Search for Extraterrestrial Intelligence” edited by Ben Bova and Byron Preiss. Okay, it’s a bit dated at 1990, but still worth a read, with articles by Isaac Asimov, Frank Drake, Arthur C Clarke and many others. It asks such probing questions as – what is intelligence? What is life? Why the heck haven’t we been contacted yet? Where is everybody?

Come to think of it, where is everybody? Of course, ancient texts are full of curious stories that resemble close encounters of the alien kind.

The Prophet Ezekiel saw four living beings glowing brightly, descending from the centre of a cloud. Each apparently had four wings and four faces, and a tall wheel rimmed with eyes. Say what?

The early Sumerians had the amphibious Oannes, a fish-like being who “gave them an insight into letters and sciences and arts of every kind. He taught them to construct cities, to found temples, to compile laws, and explained to them the principles of geometrical knowledge.” (Berossus)

Petroglyphs from Val Camonica, Italy

Others see spacemen in the 10,000-year old rock drawings of Val Camonica, Italy, or the structure of chemical formulae in the Ural pictograms of Russia.

Ancient astronaut theories abound in our literature. Writers such as Erich von Däniken, Giorgio A. Tsoukalos, Zecharia Sitchin, Robert K. G. Temple, David Icke, and Peter Kolosimo have put forward numerous theories that we were visited by aliens in our ancient past, or even that we are descended from such aliens. Astrophysicist Thomas Gold, for instance, suggested a ‘garbage theory’ for the origin of life – life on Earth might have spread from a pile of waste accidentally dumped on our lovely planet by clumsy aliens. God, in other words, is an extraterrestrial.

Comparison of some Ural pictograms to formulae of chemical compounds

Now, there is no real scientific proof for any of this. You can interpret myths, religious texts and ancient cave art any way you like. The fact is, sadly, that there is no evidence of life in the universe apart from our green and blue planet. No alien signals have been detected by the valiant SETI Institute. No hidden lasers lurk in secret tombs. The Roswell UFO incident was not about a UFO but about a weather balloon (or maybe not. Who knows?)

So are we alone in the universe?

Of course we aren’t. We can’t possibly be. Absence of evidence is not evidence of absence. And the universe is too vast, the definition of ‘life’ too broad. The question is not framed correctly. Let us ask instead, is there intelligent life out there that has developed space-faring technology? It doesn’t matter if they’re really ‘out there’, if a gazillion light years separate us from them.

Frank Drake’s famous 1961 equation defines N, the number of transmitting civilizations in our galaxy, as the product of seven factors:

N=R* f_p n_e f_l f_i f_t L

Where:

R* = the birth rate of stars in our galaxy, number per year
f_p = the fraction of stars with planet
n_e = the number of planets per solar system that are suitable for life
f_l = the fraction of such planets that actually spawn life
f_i = the fraction of planets with life that evolve intelligent life
f_t = the fraction of planets with intelligent life that produce technologically capable life
L = the average lifetime (in years) of a technological society

If you’re a pessimist, you might decide that N = 1, i.e. we are the only technologically capable species in the galaxy. Carl Sagan, that wonderful optimist, said N could be a million. Frank Drake himself put it at a more modest 10,000.

Of course, Drake’s equation needs three new factors to guess at probability of contact with an alien civilization:

V – the velocity with which an interstellar culture grows into space
Lz: The life time of a zone of colonization
A: Approach / Avoidance factor – how likely is it that a) we would notice them and b) they would approach us?

And this brings me back to the question of why we haven’t been contacted yet. What explains the Great Silence? Listed below are a few favorite explanations:

1. We are actually alone. Intelligent life is much rarer than we think, and we are the first, the ‘Elder’ race.
2.  Advanced species communicate in ways that we cannot detect, or live in dimensions we cannot conceive of.
3. We are perceived as too dangerous, the Earth too unattractive, to risk contact
4. We’re in an undesirable neighbourhood, the spiral arm of the Milky Way, exposed to cosmic debris and other dangerous events that aliens would rather avoid.
5. Most intelligent life in the universe has developed in ‘water worlds’ – beings with no hands to develop tools or use fire.
6. We’ve been contacted already – we just don’t know it.

What do you like to believe?