At first glance it seems that our civilisation is quite special. We exist in a habitable zone on a planet with large bodies of water and oxygen. Unlike the dinosaurs, we have not been hit by a major asteroid 67 million years ago. This supposed uniqueness gave rise to many religions and philosophies. I would even argue that it lead to solipsism, or the idea that everything exists only in the mind. Yet, it turns out that we might not be so special after all.
There are billions of main sequence stars that are very similar to the Sun in our galaxy. A portion of these stars has Earth-like planets orbiting them at a habitable zone distance. A lot of these stars are older than the Sun, so civilisations would have developed there long before us. If so, they likely would have developed interstellar travel. Even with our current technology, you could traverse the galaxy in a few million years. So, where is everybody?
There are a ton of explanations of this paradox. One of them states that civilisations are very far away from us and we have not listened for long enough. Humans are not an old species by cosmic standards, and radio telescope technology has existed only since the 1930s. We have received the famous Wow! message in 1977, which some people claim to be evidence of aliens. While there are many hypotheses for its origin, we still don’t agree upon one. What’s interesting is that the frequency 1420 MHz is restricted only for astronomical use. Therefore, it is unlikely that this was a commercial or military signal. However, I believe that if aliens tried to make contact, they would’ve done it more than once.
Another explanation is that advanced civilisations don’t last long enough to talk to each other. We have come close to nuclear annihilation in the Cuban missile crisis just 25 years after the first radio telescope was developed. Perhaps, civilisations self-destruct before discovering rapid methods of interstellar travel. The knowledge of radioactive processes is crucial for harvesting large amounts of power needed for a complex society. The creation of bombs follow almost immediately. Furthermore, climate change could be the destroyer of civilisations. We suspect that the chemical composition of planets that sustain life is similar to that of Earth. Therefore, using coal and oil as fuels is a straightforward choice that leads to greenhouse gas emissions.
Destruction could also come from space. Large asteroid impacts, like the meteor that wiped out the dinosaurs 66 million years ago, happen approximately every 100 million years. That gives fairly little time for civilisations to exist, since evolution needs a lot of time to happen. Nonetheless, assuming sustainable exponential growth, a lucky society could easily get tremendous communication capabilities within a million years.
One of the coolest ways, in which we have tried communicating is the Golden Record. They are two records launched on the Voyagers in 1977. The selection of what to put on the record was directed by Carl Sagan at Cornell. It has a ton of images of natural life, recordings of brainwaves and English voices. They are inspiring messages in a bottle thrown into the dark cosmic ocean. Perhaps, they will be the only thing left from our civilisation.
Koehrsen, W. (2019, February 4). Predicting the frequency of asteroid impacts with a poisson processes. Medium. https://towardsdatascience.com/predicting-the-frequency-of-asteroid-impacts-with-a-poisson-processes-98d483efa61d.
NASA. (n.d.). Voyager – the Golden Record. NASA. https://voyager.jpl.nasa.gov/golden-record/.
Wikimedia Foundation. (n.d.). Fermi paradox. Wikipedia. https://en.wikipedia.org/wiki/Fermi_paradox.
Wikimedia Foundation. (n.d.). Voyager golden Record. Wikipedia. https://en.wikipedia.org/wiki/Voyager_Golden_Record.