One thing that we all have difficulty with as we consider the issue of extraterrestrial intelligence is our inability to fully conceive just how big the universe is. Another science fiction author, Douglas Adams, wrote somewhat humorously, “Space is big. You just won’t believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that’s just peanuts to space.” To put it in some perspective, consider that it took the astronauts three days to reach the moon. If they tried to get to Mars by traveling at that same speed, it would take them over seven months. To get to Alpha Centauri, which is about four light years away, it would take them more than eighty thousand years. The pyramids were built but four thousand years ago. So multiply that by twenty.
Or think about it like this: the Voyager 1 space probe which left earth in 1977 has travelled further than any other human spacecraft: it has left our solar system. And it is barely sixteen and a half light hours from Earth—after traveling for nearly thirty-five years at more than 30,000 miles per hour.
Our galaxy, the Milky Way, is 100,000 light years across. Poor Voyager will take 14,000 years to cross even one light year.
But expressing the distances to the stars like that is only part of the concept that prevents us from considering the size of the universe and the difficulty in finding other life or intelligence. The Milky Way galaxy alone contains about 400 billion stars, which are separated by multiple light years from one another. Based on our current findings regarding the commonality of planets, there are probably at least a trillion planets in just our galaxy alone. If only one in a thousand are like the Earth—right distance, size, and temperature, then there may be a billion Earth-like worlds out in just our Galaxy—which is but one out of the hundred billion galaxies in the visible universe, which is but a fraction of the entire universe.
But remember those distances between all those worlds: light years upon light years.
And the only thing that moves at a reasonable speed is light itself, and even that’s not so fast given the vast size of the universe: a hundred thousand years would pass before the light of a star on one side of the galaxy reached a star on its opposite end: the time between us and the pyramids multiplied by twenty-five. Or if we think in terms of the voyager space probe, multiply the 14,000 years it takes it to travel even one light year by 100,000.
Human beings have been broadcasting television and radio signals for barely a century. Our recorded history spans about 6000 years. Thus, for only for 1.6 percent of our history have we been making noise that the rest of the universe might hear. And only a tiny fraction of one percent of the stars in our galaxy can hear it. Traveling at light-speed, our broadcasts form a bubble of babblings that stretch a hundred light years or so. Within that hundred light year bubble scientists estimate there are about 14,600 stars. Most of those stars we know nothing about and they don’t even have names.
And even if there are civilizations within that hundred light year bubble, what are the odds that they and we both have similar and compatible technologies at roughly the same time? What if the closest civilization has the technology of Victorian England? After all, a civilization a hundred twenty light years from Earth would, in fact, be listening to our Victorian era. Our first radio broadcasts wouldn’t have gotten out to them for another twenty years.
But even if a civilization fifty light years from us is using television, we currently lack the technology to pick up any of their signals. Their broadcasts would be drowned out in all the other noises of the universe. It would be worse than trying to pick out a single conversation in a football stadium full of fans. Or worse than picking out the flame of a match in front of a spotlight.
Space and time are both vastly deep; we have been here so briefly and are so tiny, that it is unsurprising that we can’t notice anyone else out there. Finding another civilization would be like picking out the million grains of sand that you engraved your name on out of the Sahara desert after they’d been scattered across it by a high flying jet –as you stand on a stepstool at its edge.
Even if we find a way to travel to the stars quickly, as in Star Trek, it will still be hard to find those “new civilizations” as we boldly go where no one has gone before. There might be thousands of grains to sift before we find even one with life. And then if we find people—what percentage will be at a technological level that saying “hi” would be a good idea?
No one has visited Earth yet that we know of. Chances are, no one has even glanced in our direction. We—and the supposed they—are tiny. So mind-bogglingly tiny in an immensity beyond comprehension.