Why haven’t we heard? I’m not talking about a First Contact – how about just an accidental eavesdropping onto some alien radio broadcasting? Here is an interview with Davies, and John Derbyshire outlines the speculation nicely (below). I admire his honest humility at the end. Mine (personality, not honest humility!) steers me to 1.
The silence is a bit of a mystery. Based on what we currently know about how planets form and how complex creatures evolve from simpler ones, and our best guesses (that’s all they are) about how life arises in the first place, our stage of development should have been reached billions of times over on other planets — millions of times just in our own galaxy.
Having gotten to our stage of development, these other beings would presumably have kept going past it. If the chain of events that led to us happened just 1 percent faster elsewhere, those beings are now 140 million years ahead of us (age of universe — 14 billion years: 1 percent of 14 billion — 140 million). That’s about the distance between us and the earliest mammals — little rat-like creatures trying not to get stepped on by dinosaurs.
So . . . where are they? We’ve been listening for 50 years, and heard squat. There are a number of explanations:
1. What we think we know is all wrong. Intelligent life is so fantastically improbable, we are the only specimen, or else the nearest other specimen is a billion or so light years away.
2. Radio communication is a brief, transient phase in the development of civilization. Some civilizations may leapfrog it, never using radio at all.
3a. Civilization may be self-annihilating. Once a civilization has unlocked the secrets of the atom, it may then inevitably happen that it destroys itself, either (most popular with sci-fi writers) in a species-suicidal war . . .
3b. . . . or (more likely in my opinion) by prying too deep into the nature of reality, turning its planet — perhaps its entire stellar neighborhood — into subatomic trash. Curiosity killed the cat: it might kill us, and any other civilization that gets to our level. Manhattan Project physicists seriously discussed the possibility that a fission bomb might destroy the Earth’s atmosphere. It didn’t, of course, and they called that one correctly; but sooner or later, setting up some other experiment, we may get it wrong and turn the entire solar system into fine dust, or dark matter, or nothingness.
4a. It may inevitably happen that technological civilization leads quickly to a singularity, on the other side of which is a state of existence we cannot guess at, let alone understand, let alone communicate with. It may even be that . . .
4b. . . . this happened just once, creating a malign Power that could police the entire universe, preventing the rise of any rival Power by wiping out species that get too close to Singularity.
5. High intelligence is an evolutionary dead end, always and everywhere. It’s just inevitably dysgenic. A creature that gets smart enough will stop reproducing and get numerically swamped by dimmer but more philoprogenitive creatures, possibly of its own species or genus. Neanderthals seem to have had brains slightly bigger than ours. Perhaps they were the smart species and we were the dumb one. Just as there’s a Whig interpretation of history, so there’s a Whig interpretation of evolution, assuming that there’ll be creatures in a later epoch much smarter than any of the creatures of an earlier epoch. I can’t think of any strong reason why this should be so. Why shouldn’t a trait just max out, as size did with the dinosaurs?
Since our actual knowledge in this area is very scanty, any one of these is as probable as any other. Which one you favor is a function of your own personality. For myself, I like 3b. It just seems the neatest.