The universe is constantly expanding and, at its current diameter of 93 billion light years, it’s beyond a size that we can imagine. In all that space, it seems obvious that there must be something else out there, yet we still don’t have any proof.
In 1950, physicist Enrico Fermi was very interested in this apparent contradiction between the high probability of alien life and the lack of evidence that any such thing exists. His theory, known as the Fermi paradox, pointed out that there are billions of stars that are similar to the sun in size and temperature that are significantly older. He also said that it’s very likely that there are planets like Earth that are a similar distance from those stars, according to Britannica. Intelligent life, then, should have spawned long ago. With a billion-year lead on Earth, it’s not unrealistic to postulate that those civilizations could have developed interstellar travel and visited us. Yet there’s no evidence that this has ever happened.
From here, many have posited their own ideas to explain the discrepancy, like the Great Filter, conceived by economist Robin Hansen in 1996. He believed that the lack of evidence towards the existence of aliens could mean that there were once aliens, but something went wrong. He hypothesized that there could be a metaphorical filter that greatly reduces the number of civilizations with intelligent life, according to ABC.
One of the evolutionary phases that life goes through on Earth must be very rare, he thought, according to Astronomy.com. If one of the earlier steps (such as the formation of multi-cell life) is not improbable, then that could mean that our filter is something that awaits us in the future, like nuclear warfare or the effects of climate change.
The idea behind this filter is that the easier the past was for us (and the hypothetical aliens), the bleaker the future will look. And maybe that’s why we haven’t seen any aliens: they didn’t survive long enough to meet us.
Even though many theories like this argue that the likelihood of contact with aliens is slim, humans still hold out hope, and continue sending messages into the void hoping for a response.
The most famous of these missions was the launch of Voyager 1 and 2, the first space crafts to leave the solar system, in 1977. They both carried the same golden audio-visual disc, containing information for any alien life that might find them as they wandered forever, according to NASA. Through 116 images, greetings in 55 different languages and a variety of music, the discs sought to capture what life was like on Earth and, with little chance of erosion in space, they’re estimated to remain intact for nearly a billion years.
Drifting endlessly, it’s unlikely that Voyager will wander its way to intelligent life. Intelligent life will have to find it, and hopefully they’ll understand our message: we exist, and we wanted to say hello.