(CLICK AND ENLARGE ABOVE: a great quote by Arthur C. Clarke – – “Two possibilities exist; either we are alone in the universe or we are not – – both are equally terrifying”)
by Stephen Hawking, LIFE IN THE UNIVERSE Lecture:
What is the explanation of why we have not been visited?
One possibility is that the argument, about the appearance of life on Earth, is wrong.
Maybe the probability of life spontaneously appearing is so low, that Earth is the only planet in the galaxy, or in the observable universe, in which it happened.
Another possibility is that there was a reasonable probability of forming self-reproducing systems, like cells, but that most of these forms of life did not evolve intelligence.
We are used to thinking of intelligent life, as an inevitable consequence of evolution.
But the Anthropic Principle should warn us to be wary of such arguments.
It is more likely that evolution is a random process, with intelligence as only one of a large number of possible outcomes.
It is not clear that intelligence has any long-term survival value.
Bacteria, and other single cell organisms, will live on, if all other life on Earth is wiped out by our actions.
There is support for the view that intelligence, was an unlikely development for life on Earth, from the chronology of evolution.
It took a very long time, two and a half billion years, to go from single cells to multi-cell beings, which are a necessary precursor to intelligence.
This is a good fraction of the total time available, before the Sun blows up.
So it would be consistent with the hypothesis, that the probability for life to develop intelligence, is low.
In this case, we might expect to find many other life forms in the galaxy, but we are unlikely to find intelligent life.
Another way, in which life could fail to develop to an intelligent stage, would be if an asteroid or comet were to collide with the planet.
We have just observed the collision of a comet, Schumacher-Levi, with Jupiter.
It produced a series of enormous fireballs.
It is thought the collision of a rather smaller body with the Earth, about 70 million years ago, was responsible for the extinction of the dinosaurs.
A few small early mammals survived, but anything as large as a human, would have almost certainly been wiped out.
It is difficult to say how often such collisions occur, but a reasonable guess might be every twenty million years, on average.
If this figure is correct, it would mean that intelligent life on Earth has developed only because of the lucky chance that there have been no major collisions in the last 70 million years.
Other planets in the galaxy, on which life has developed, may not have had a long enough collision free period to evolve intelligent beings.
A third possibility is that there is a reasonable probability for life to form, and to evolve to intelligent beings, in the external transmission phase.
But at that point, the system becomes unstable, and the intelligent life destroys itself.
This would be a very pessimistic conclusion.
I very much hope it isn’t true.
I prefer a fourth possibility: there are other forms of intelligent life out there, but that we have been overlooked.
There used to be a project called SETI, the search for extra-terrestrial intelligence.
It involved scanning the radio frequencies, to see if we could pick up signals from alien civilizations.
I thought this project was worth supporting, though it was cancelled due to a lack of funds.
But we should have been wary of answering back, until we have developed a bit further.
Meeting a more advanced civilization, at our present stage, might be a bit like the original inhabitants of America meeting Columbus.
I don’t think they were better off for it.
Norio Hayakawa’s CIVILIAN INTELLIGENCE NEWS SERVICE
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