Physicist Brian Greene Has a Theory on Why Aliens Haven’t Visited Us

When you think of human evolution, do you ever stop to think what are we going to be like a million years from now if we do survive? Have you ever done this sort of thought experiment where you say, okay, if things keep going the same way, we used to be very strong and very hairy, and we're getting progressively softer as we don't need to use our bodies as much. Our brains are getting larger, our heads are getting bigger. Do you do that sort of thought experiment to see what we're going to be common? Not in a systematic scientific way because the process is so fraught with incredible detail that I think it's hard for anybody, even experts in evolutionary biology, to really tell us anything that will hold water that's really predictive. But on a general level, yeah. I mean, because people often wonder why is it that we haven't been visited by aliens, right? And it's something that comes up whenever you're talking about other life inside the universe. I'll give you that in a minute. Yeah. Yeah, yeah. But the answer to that could be quite straightforward. Nobody out there cares about us because we're so ill-developed, we're so young on the cosmic scene that there's nothing interesting for them to find here on planet Earth. So to me, there's a natural explanation for why there can be stuff of other life out there, and yet they don't hang out around planet Earth just so we don't hang around in an ant hill to try to have a conversation with what's going on inside that particular structure. I buy that argument the least. You do? Really? Because we're interested in butterflies. Butterflies are so boring. We're interested in moles. We're interested in squirrels. We're interested in them for very specific reasons, right? Sure. So typically, we're interested either because we want to see the evolutionary development that yields this particular life form, or because there's a general curiosity about how this object is put together. If these other beings are so far beyond us that those kinds of taxonomy questions are no longer of any interest, then hanging around here may not hold anything for them to make the journey and stick around long enough for us to notice. I don't buy that again for two reasons. One, because why would we assume that they're so far beyond us that they wouldn't be interested in these talking monkeys with thermonuclear weapons who dominate an entire planet? That would be fascinating. We found some planet somewhere where people are – the politicians all lie to themselves. Everyone gets video through the sky. They fly in metal tubes that hurl over the oceans. They pollute the oceans and eat all the fish. These people are fucking crazy. We've got to go there and check this out. But imagine that this civilization, the notion of lording over a planet is like us talking about the ant lording over a grain of sand. They may be galactic as opposed to planetary in their hegemony. The notion of some little tiny rock orbiting some nondescript star in the suburbs of this completely ordinary galaxy off there on the side may not have the kind of pull that you imagine that it does. Oh, I disagree. We think it's interesting when we see a champion use a rock to open up a nut. We think it's interesting that there's an amazing photograph of an orangutan that's spearfishing. Have you ever seen it? I have seen that actually. Yeah, yeah, yeah. Right. No, it is. He learned it from people apparently, but it's still interesting nonetheless. Right. But I don't think 100 years from now we're going to be as interested in these kind of qualities or a thousand years from now or 10,000 years from now. Well, why would we assume that these things that come here from another planet are more than 10,000 years? Well, that's a good – that's a very good question. And I think the answer to that is we look at the history of the cosmos until today and it's – let's just call it our universe to be concrete, 13.8 billion years. And we look at life on planet Earth and it's a handful of billions of years old. So in a handful of billions of years you can go from some complex molecules to human beings. I like how you say it like it's not that long. It's not that long because imagine that life began a few billion years earlier in some other system. Stars and galaxies, they were starting up a billion years after the Big Bang. So it could be that life in other worlds has a head start on us by a few billion years. And we know what can happen in a few billion years. It can take us from single cell to us. Sure. And you can imagine from a few billion years from now into the future it could be radically different. So to say it's 10,000 years ahead of us, that to me would be the unexplained coincidence. How unlikely that they started and we started within 10,000 years in the span of billions of years. That seems unlikely to me. Does it seem unlikely when you're talking about the infinite size of the universe and there's perhaps an infinite number of Brian Greenfield there talking to an infinite numbers of me? Good point. Good point. So you're absolutely right. You're guaranteed if the spatial expanse of the universe is infinitely large that there are going to be places where it's within 10,000 years. But those are going to be a very small number compared to the places where it's not 10,000 years. Is that true or would it be an infinite number of them? Well, it'd be infinite. Not a small number at all. But there are different kinds of infinities. So you mean in the space of the exact scope of the universe itself, a small number, relatively speaking to where we are physically. Yeah. So I would say slightly differently. Look at a finite size ball in this large spatial expanse. So everything's finite now. So let's get a 5 billion light year ball. And within that ball, the number that are differing from us by 10,000 years will be very, very small compared to the number differing from us by say a billion years or a couple of billion years. So then simply by the law of numbers, if we imagine that the random processes that are trying to… Now there could be some physical principle that prevents life from emerging before say four billion years ago. And if that's the case and we're not aware of that principle, then you'd be absolutely right that we'd all be roughly at the same starting point and there's no reason to suspect that they would be so far ahead of us. But I don't know of any such principle. But yeah, you almost have a reductionist view of this, right? So if you had a guess, if you had $100 to bet, has alien life ever observed us? You would say no. Well, by observed, you mean could they just turn a big telescope in our direction and gather some radio waves? You know, but yes, I would take that bet because frankly, we've only been generating radio waves for the last 70 years. So it's only a 70 light year ball around us. And within that small radius, very unlikely that there's been some alien world that's examining us. So it would have to be something that would be able to recognize our signal and visit us. Right. But don't we look at observable planets and solar systems and discover Goldilocks planets? We do. And we examine those planets from vast distances away. Yes. And wouldn't you assume that a life form that is perhaps thousands of years more advanced than us with the exponential increase in technology, I mean, if they ever got to the point where we are, that they would see these Goldilocks planets as well and recognize that Earth is one of them. Yes. However, if they are so far away, they're going to be examining Earth as it was hundreds of thousands or millions or billions of years ago. So if you truly want them to be examining us in the sense of human presence on planet Earth, then it's a much more difficult proposition to imagine that they've actually been doing that. Is it possible there's another way to examine things where you're not hampered by the speed of light? No, not that I know of. I mean, any signal in the world that we're aware of is restricted by the speed of travel. The speed of travel. Now look, there's quantum entanglement, which is a strange property of the quantum world in which distant objects can behave as if they are one and in some sense respond instantaneously to an influence in one location at a distant location, no matter how far apart they are. But that isn't really observing. That's more realizing correlations between physical properties at widely separated locations. But I'm not aware of a means of leveraging that to actually observe what's happening in some distant location, even if you do have quantum entangled particles.