Alien Life

I heard a scientist say that because of the vast number of planets in the galaxy, it is almost certain that alien life exists. My reaction: hmmm.

Frankly, I have no idea what the odds may be for life originating on a planet or moon, and anyone who tells you they do is seriously delusional. Given enough time, life may be inevitable. Or life may be a fantastic fluke. No one knows for certain how life got started on Earth.

Let’s divide alien life into four types. Type 1 is all life excluding intelligent life (on a par with human intelligence). Type 2 life is intelligent but not technologically advanced. Type 3 life has technology that is emitting radio waves. Type 4 life has advanced beyond radio and no longer uses it.

Scientists are looking for life in the galaxy by listening for artificially-produced radio transmissions. That means they’re looking for type 3 life. The galaxy might be loaded with bacterial life, but only a biologist is going to get excited over that discovery. Ordinary people are only going to get excited over type 3 life (or type 4 life, which we aren’t searching for because we don’t know how). Type 3 is the only kind of life that will be discoverable by humans unless we find a way to go out into the galaxy and examine planets and moons, and that will not happen for a very long time, if ever. Science fiction dramas notwithstanding, the galaxy is simply too immense. “How immense is it?” you ask. Allow me to quote from a previous blog post titled Laniakea.

If we shrink space so that our Milky Way galaxy has the diameter of the Sun, then the Sun’s diameter will be about the thickness of a dime, and the Earth’s diameter will equal the thinnest human hair. And if you are a human who is 6 feet (1.83 meters) tall, how tall would you be in our shrunken galaxy? You’d be 2.45 millionths of a micrometer tall. What else is that small? Not much. In fact, it would take a thousand of you, lined up head to toe, to equal the length of the smallest virus humans have studied.

So we’re pretty much stuck with trying to detect, not any alien life, but only alien life that is using powerful radio transmitters with antennas that, through sheer happenstance, are pointed our way at the very moment we’re listening for them. Well, not literally at the moment we’re listening. A civilization 10 light years from us would have to have transmitted a signal our way 10 years ago for us to detect it today.

A century, or ten centuries, from now, it’s very possible that humans will no longer use radio waves for communication. The same could be true of alien technology. So let’s be generous and assume that our radio civilization will last for 1000 years before our radio technology is replaced by a new technology. That means our search for alien life is limited to life that has advanced to at least our level of technology but not much beyond it – a thousand year slice of time.

An alien civilization’s solar system is likely as old as our own. Our solar system is 4.5 billion years old but, for perspective, let’s scale that down to one day (24 hours). If we do that, a radio civilization that lasts for 1000 years will then exist for two hundredths of a second, or twenty milliseconds. If all of Earth’s history were to be compressed into a single day, 1000 years would pass faster than the eye can blink. It’s not surprising that we haven’t found life out there. If intelligent alien life exists, it will take a large amount of luck and extremely fortuitous timing for us to detect it. The odds of success are not good. But we have to look. Because sometimes, against the odds, that stroke of luck happens.