Transcription
There have been billions of years on billions of worlds for civilizations to arise. We see no evidence of any of them in the Galaxy at all. The question is, where are they? By “they,” I mean aliens. [Music] The question is, where are they? By “they,” I mean aliens. The Fermi Paradox, at its heart, is that there have been billions of years on billions of worlds for civilizations to arise. We see no evidence of any of them in the Galaxy at all. So the Paradox is: why?
A possible answer is because the Earth is pretty much unique in the Milky Way galaxy in that the climate, the conditions on Earth were stable enough for long enough for life to go from cell to civilization. You think about that—that’s a big ask. We know that we live in a violent universe, so maybe, maybe it’s the case that whilst there are billions of planets which may have liquid water on the surface, may have oceans that can support life, it may be that none of those planets in the Milky Way galaxy have been stable enough for long enough to produce civilizations. So that would be a property of the planet itself.
Another explanation for the Fermi Paradox might be that civilizations live and die; they rise and then they fall. And because of the sheer time scales involved and the sheer size of the Galaxy, no two civilizations ever overlap.
Another possibility is that it’s not a paradox; they are here. So there are intelligent civilizations out there, and they are present in the solar system. They could have sent nano-machines to our solar system; there could be probes all over the place. But if they’re the size of an iPhone, then we’d have no way of detecting them. So it could be that the technology of a sufficiently advanced alien species, a civilization, is so beyond anything we can comprehend or detect that we haven’t seen it. And that’s certainly entirely possible.
Now, it’s possible that there are many civilizations out there, but the advanced civilizations choose to remain hidden. Let’s imagine that civilizations, when they get technologically advanced, also get intellectually, morally advanced. Let’s say they choose to remain hidden because they don’t want to draw attention to themselves. Maybe that’s a logical thing to do. I find it difficult to believe, given human history, that that’s the way intelligent civilizations behave. We certainly haven’t made any attempt to remain hidden so far. We’ve broadcast radio signals out to the Stars. We’ve launched our space probes, like Voyager, which shows the location of our solar system should any other civilization find it. We’ve tried, at every opportunity, to broadcast our existence.
There’s an idea in this field trying to explain the Fermi Paradox called the Great Filter. So let’s think about what it would mean for a Great Filter to lie in our future. That would mean that civilizations do arise in the Milky Way galaxy and get to somewhere like the position that we’re at now. So they develop rocketry, they develop nuclear power, nuclear weapons, for example; they industrialize. But then there’s a filter in the future that stops them becoming true space-faring civilizations; so stops them becoming multi-planetary species and stops them ultimately traveling between solar systems to begin to colonize a Galaxy. So why might that be?
I don’t think it’s technology. As far as I can see, I don’t see anything in the laws of nature, in principle, that would stop us from becoming an interstellar species. It could be that our knowledge, our scientific prowess, exceeds our wisdom, exceeds our political skill. It could be that once a civilization develops the means to destroy itself, in the form, for example, of nuclear weapons or biological weapons, or maybe uh, some kind of uh, lack of control of AI. If you look back through our recent history, there have been several occasions that we know about where we came very close to destroying ourselves, or at least setting us back to the Stone Age, for example, where there could have been nuclear launches and weren’t. I’m sure there are many others that we don’t know about. There’s the challenge of climate change; we’re completely incapable of coming together at the moment as a global civilization to address that challenge. That could set our civilization back.
So it might just be almost a law of nature. I guess why we see no evidence of other civilizations out there is because there aren’t any, and they never have been any. The reason I guess that—and I emphasize it’s a guess—is biology. So if you look at the history of life on Earth, then we see that life began 3.8 billion years ago, let’s say, but then we see for the best part of three billion years on this planet that there’s nothing more complex than a single cell. And there could be good biological reasons for that. One that springs to mind is the evolution of what’s called the eukaryotic cell, which form all multicellular living things on the planet. Those cells, which seem to be prerequisite for complex multicellular life, evolved once on this planet, as far as we can tell. And so it seems that there’s a very unusual evolutionary event at some point that laid the foundations for us. If it typically is the case that it takes 4 billion years from cell to civilization, then I think there may be very few planets in a typical Galaxy which is stable enough for long enough for that process to, to, to proceed.
I think there’s one civilization in the Milky Way galaxy, and that’s us, which, by the way, means that we have a tremendous responsibility not to mess this up. That means the Earth is the only island of meaning in a sea of 400 billion suns. And so if we destroy this, we might destroy meaning in a galaxy forever. However, that’s a, that’s a hypothesis. I will be delighted if it turns out that’s not true. [Music]