The Fermi paradox is the observation that, although there are billions upon billions of stars, we have not discovered any evidence of intelligent life. The question is, “Why not?”
Enrico Fermi
Cosmologists make the assumption that humans, and Earth, do not occupy a privileged place in the Universe. We’re on an unremarkable planet, orbiting a typical star, in a galaxy that is one among many billions of other galaxies. This assumption is sometimes referred to as the Copernican Principle. There’s no reason to think we’re special.
With so many stars, it seems unlikely that we’re the only intelligent life in the Universe. The sheer numbers of stars would seem to guarantee other intelligent civilizations. And yet, we don’t see them.
There can be many explanations. The most obvious – and discouraging – is that we don’t see them because they’re not there. We’re the only intelligent life in the Universe. We’re all alone. I don’t think this possibility is considered likely, but… we have no proof that it’s not true.
We may be the first civilization to develop technology for communications. There are no intelligent civilizations who have the technology to hear us. Being first goes against the idea of our not being special; but someone had to be first. The Copernican Principle is an assumption, not a confirmed observation.
It may be that our technology is inadequate. Possibly there is some other means to communicate that we haven’t yet discovered. In this case, we simply wouldn’t be able to pick up the signals from the advanced civilization.
Civilizations rise and fall. Species flourish and then go extinct. In the vastness of time, it may be that civilizations don’t exist at the same time. By the time one civilization can send signals, previous ones have already fallen… and newer ones haven’t yet learned how to send signals.
There are other technical considerations. A signal meant to be heard at interstellar distances would have to be extremely powerful, especially if the signal is undirected. Power could be saved if the signal were aimed at a target – but how would a sender know which target to choose? Possibly we haven’t heard a signal simply because one hasn’t been aimed at us.
The sheer immensity of the Universe, of even the Milky Way, may mean that messages from other civilizations haven’t had time to reach us yet. There are estimated to be only about 500 G-type stars within 100 light years of our Sun. Most of the stars in our galaxy are many thousands of light years distant. It may be that the signals haven’t had time to reach us. And if they ever do reach us, then what? Certainly we couldn’t reply in a meaningful way. Our reply message would take thousands more years to reach the sender – who might no longer be there to receive the message.
All of these possibilities assume that an advanced civilization will want to continue to expand outward, to explore and exploit resources. The idea is not unreasonable. It may nevertheless be wrong. We may expect other civilizations to have similar goals to our own, but this might not be true.
I think that at some stage in its development, an intelligent civilization may decide to stop its outward expansion. The limitations of travel and communications over interstellar distances convinces them that there is no point trying.
I think advanced civilizations simply turn inward, keeping their population at a sustainable level, living within the resources of their planet or solar system, pursuing philosophical or metaphysical goals.
The Fermi Paradox
The Fermi paradox is the observation that, although there are billions upon billions of stars, we have not discovered any evidence of intelligent life. The question is, “Why not?”
Cosmologists make the assumption that humans, and Earth, do not occupy a privileged place in the Universe. We’re on an unremarkable planet, orbiting a typical star, in a galaxy that is one among many billions of other galaxies. This assumption is sometimes referred to as the Copernican Principle. There’s no reason to think we’re special.
With so many stars, it seems unlikely that we’re the only intelligent life in the Universe. The sheer numbers of stars would seem to guarantee other intelligent civilizations. And yet, we don’t see them.
There can be many explanations. The most obvious – and discouraging – is that we don’t see them because they’re not there. We’re the only intelligent life in the Universe. We’re all alone. I don’t think this possibility is considered likely, but… we have no proof that it’s not true.
We may be the first civilization to develop technology for communications. There are no intelligent civilizations who have the technology to hear us. Being first goes against the idea of our not being special; but someone had to be first. The Copernican Principle is an assumption, not a confirmed observation.
It may be that our technology is inadequate. Possibly there is some other means to communicate that we haven’t yet discovered. In this case, we simply wouldn’t be able to pick up the signals from the advanced civilization.
Civilizations rise and fall. Species flourish and then go extinct. In the vastness of time, it may be that civilizations don’t exist at the same time. By the time one civilization can send signals, previous ones have already fallen… and newer ones haven’t yet learned how to send signals.
There are other technical considerations. A signal meant to be heard at interstellar distances would have to be extremely powerful, especially if the signal is undirected. Power could be saved if the signal were aimed at a target – but how would a sender know which target to choose? Possibly we haven’t heard a signal simply because one hasn’t been aimed at us.
The sheer immensity of the Universe, of even the Milky Way, may mean that messages from other civilizations haven’t had time to reach us yet. There are estimated to be only about 500 G-type stars within 100 light years of our Sun. Most of the stars in our galaxy are many thousands of light years distant. It may be that the signals haven’t had time to reach us. And if they ever do reach us, then what? Certainly we couldn’t reply in a meaningful way. Our reply message would take thousands more years to reach the sender – who might no longer be there to receive the message.
All of these possibilities assume that an advanced civilization will want to continue to expand outward, to explore and exploit resources. The idea is not unreasonable. It may nevertheless be wrong. We may expect other civilizations to have similar goals to our own, but this might not be true.
I think that at some stage in its development, an intelligent civilization may decide to stop its outward expansion. The limitations of travel and communications over interstellar distances convinces them that there is no point trying.
I think advanced civilizations simply turn inward, keeping their population at a sustainable level, living within the resources of their planet or solar system, pursuing philosophical or metaphysical goals.