In our tiny corner of the Universe, we know (to the best of our limited knowledge) that we’re the only intelligent species that exists. But space is vast and we can still send a message across even if we don’t deliver it personally. What message should we send, and how?
First, let’s talk about language. Our language has evolved over centuries in different civilizations. Some languages have symbols like A-Z to represent their alphabet, while others like Chinese use pictures. I think it is fair to say that an alien would understand neither. What language would be a common ground between humans and aliens? The answer is Mathematics. Even if an alien did not use a decimal system, we have good reason to believe that the laws of mathematics are truly universal. The value of pi remains the same in decimal or binary or whatever representation an alien would choose to use. As a means of communication, an alien would certainly be interested that we as a species were aware of Newton’s laws, Einstein’s theories of relativity, and so on.
Next, consider the form. Sending a signal through radio waves sounds reasonable at first, but these get considerably weaker as they travel. Sending a physical device is another approach, but it is impossible to target it when you don’t know the destination. The probability of aliens locating, accessing and decoding a tiny probe in the vastness of space is tiny indeed. But we are nothing if not ambitious. The Voyager space probes are doing exactly this. We have carved messages in Gold records and shipped them in these spacecrafts. (The records are made of Gold because it is a noble metal and is very resistant to corrosion, so we expect this message to last for centuries if not more.)
Finally, consider the content. What could we conceivable talk about that would impress an alien civilization? Lewis Thomas considered this in his book “The Lives of a Cell”. For him the answer was obvious. “Send Bach. All of Bach”, he said. A more detailed answer was given by a team led by Carl Sagan that constructed the contents of the Voyager records. They took a wide rather than deep approach. Some of the sounds include those of Whales, laughter, wind, rain, vehicles and so on. We feel music is a universal language, so there is a lot of music from a variety of cultures the world over. There are images of humans, the earth’s place in the solar system, and so on. And most importantly, there is a pictorial representation of how to decode and play back the images and audio.
Attempts like these are ultimately hopeful rather than practical. They provide an opportunity to see and represent humanity’s best side in a message that will outlive us all. For non-experts like us, they provide fertile ground for thinking about how to communicate across cultures and finding common ground.