The science of exploring the unknown is complicated, mainly because we don't know what we don't know – so how to find it? Usually, we try to apply things we are familiar with and just multiply them or make a theoretical assumption of what they will be when developed much further.
But our own history tells us that very often we don't progress by developing old solutions. We jump to new ones. New methods, new technologies, new discoveries. So, if we search for intelligent life in the universe, we can't limit ourselves to the method that happens to be the favored one on earth at this point in time.
Radio waves travel by the speed of light, of course. That's fine when communicating around the earth. Any destination on earth is reached in a fraction of a second. But for sending messages across the cosmos, that speed is completely unsatisfactory. It takes four years just to send a message to the nearest star outside our solar system, and just as long to get the response.
Advanced civilizations wishing to communicate with other planets in our galaxy or beyond it have to find other methods. They must go beyond the speed of light, or there's not much point to it. They wouldn't even know if other civilizations still exist, once they hear from them.
So, to search for extraterrestrial intelligence we need to search for communication exceeding the speed of light. We don't know how to do that yet, but therefore it's also too early to call it impossible.
As far as I understand, the speed of light is not the highest speed there can be. The present laws of physics just state that something traveling below that speed can't accelerate beyond it – and vice versa. But there can be things traveling constantly beyond the speed of light. Maybe that's what interstellar communication is all about.
I don't know. I just have fun speculating. I'm watching episodes of Through the Wormhole and my mind goes in a spin.
As for aliens, I was sure of their existence already in my early teens. To me it was simple: There are so many stars in the universe, surely also even more planets, considering how they are formed, so there just has to be a multitude of planets with life, some of it surely at least as intelligent as ours.
To my surprise, physicists at that time (the late 1960's and early 1970's) were much more doubtful, not to say categorically opposed to the idea. I think they were irritated by the speculations going on in science fiction, which they tended to regard as amateurish nonsense.
They've changed since. Today, most astronomers take almost for granted that there is plenty of life in the universe, and therefore by necessity also intelligent life. They agree to the simple statistics of it.
But aliens don't come and greet us, as far as we know. They're just as elusive as the gods we've worshiped through history. Astronomers explain it with the law of physics rejecting travel even close to light speed.
The aliens might be spying on us from their own planets. But if so, they only have our radio signals to read, which have only been transmitted for a little more than a hundred years. That doesn't go very far in our vast cosmos. So, most of the aliens are yet to discover us.
Still, I would be surprised if it turned out that we've never ever been visited by aliens. If they could reach us, they'd be a lot more advanced than us, so they'd make sure not to interfere with our emerging culture – like we do when we study wildlife in nature. They would think that there's a time for everything and nothing good comes out of rushing things.
But they would be curious. Life is like that. Once you're aware of being alive (see my previous blog post), your curiosity grows and you want to know all about it. So, of course you want to have a look at other species reaching the same awareness.
They might even secretly interfere at times of dire need, just to make sure that we survive as a species – in spite of our self-destructive tendencies – because they are curious to see how we turn out, eventually.
To find out if aliens from a civilization that has to be superior to ours have visited us, we have to think like them. That's not easy. So, it's kind of a self-adjusting principle: We find them when we are able to understand them.