We might actually be alone in the universe, and the reason is quantum mechanics
Quantum mechanics, the multiverse, and why we haven’t met E.T. yet
Before I begin, a disclaimer: No one has a clue if we’re alone in the universe.
So to be clear here, I’m actually not going to try to convince you either way.
Instead, I’m going to try to convince you that if we are alone, something very weird is going on — and that the parallel universes of Many Worlds quantum mechanics might provide one of the only possible explanations for our existence.
A cosmic coin toss and the life conspiracy
Let’s imagine that the universe uses a coin flip to decide whether or not life is going to evolve on a given planet.
That coin is going to be biased: rather than landing on “life-side-up” 50% of the time and “life-side-down” the other 50%, it’s going to strongly favour the “life-side-down”, no-evolution outcome. At least, it seems that way so far — life is 1 for 9 in our solar system alone, for starters, unless you’re some kind of Pluto-denying psychopath.
To bias things in this way, we could imagine just adding some weight to the “no-life” side of the coin — the more weight we add, the more unlikely it is that life will evolve on a particular planet.
In the actual universe, rather than adding weight to one side of a coin, you could bias planets against life by tweaking a few key cosmological parameters with complicated-sounding names, like the gravitational coupling constant, the cosmological constant, the speed of light, etc.
But the idea is the same: we can imagine a kind of grand cosmic dial that controls the probability that life will evolve on every planet in the universe, just like adding weight to one side of a coin.
So, how biased does our cosmic coin have to be if we’re alone in the universe?
Let’s figure that out: if there were only ten planets in the universe, then to maximize the chances of life appearing exactly once, you’d need to bias the coin to be “life-side up” one time in ten, or 10% of the time.
Not 30%, or we’d expect life to evolve 3 times in this ten-planet universe. And not 3%, or we’d expect on average to find no life at all. But 10%.
Of course, there aren’t 10 planets in the universe. There are around 100 000 000 000 000.
So if we are alone in the universe, our cosmic coin has to be really carefully balanced. Because you’d need the odds of a “life-side-up” outcome on any particular planet to be somewhere around 0.000 000 000 001%.
That’s a very specific number. So specific that it’s hard to imagine that by pure chance things just happened to stack up this way.
So, is some kind of cosmic conspiracy at play here?
Quantum mechanics and the impossibility of life
Ok, so it seems like the probability for life to evolve on a given planet would have to have been balanced incredibly precisely — to something like 0.000 000 000 001 % — in order to explain our existence, if we are alone in the universe.
And assuming the universe could have biased the coin any way it wanted, it seems reasonable to ask: why isn’t the number way bigger, or way smaller?
Well, maybe it is.
Suppose that our cosmic coin is more biased against life than we could possibly imagine. So biased, that even in a universe the size of ours, we’d expect virtually zero chance of any life — intelligent or otherwise — coming into existence.
“Hold on, smartass,” you say. “Then how do you explain life on Earth?”
Two words: parallel universes.
Parallel universes might explain why we’re alone
It turns out that quantum mechanics strongly hints at the existence of parallel universes. You can read about why that’s the case here, but let’s quickly run through how this works:
Picture a tiny particle, like an atom. If you think of all the things the atom could do in the next fraction of a second, you’d have quite a long list: it might move to the left, move to the right, move up, move down, jiggle a bit, spin clockwise, etc, etc.
What quantum mechanics says is that the atom never actually chooses to go with any one of those options, and instead does them all at the same time.
It’s essentially living out a kind of subatomic split personality disorder.
And since that’s happening to every atom and subatomic particle in the universe, the end result is that essentially, anything that can happen does happen — in a different branch of the multiverse (or “universe”).
So the multiverse ends up exploring every combination of particle positions and orientations that’s physically possible, each combination of which gives rise to a different universe. And since one of those combinations leads to the evolution of the human species, well: here we are, in that particular branch of the multiverse.
So as long as it’s at least possible for life to evolve, it will evolve in some branch of the multiverse. Even if the odds are way, way lower than 0.000 000 000 001%.
The multiverse and the anthropic principle
“If the odds of life evolving are basically zero, then how come I just happen to be in the branch of the multiverse where humans evolved?”
In the universes where life never evolved, there are no humans around to look at their surroundings and go, “hey, cool! A universe where we didn’t evolve!”
That’s the anthropic principle in a nutshell: if the multiverse is real, there really isn’t anything strange about the fact that we find ourselves in exactly the kind of universe that would allow for our own existence. In fact, we couldn’t help but for that to be the case.
If we really are alone, there’s probably a multiverse
If life is phenomenally unlikely, there are going to be way more branches of the multiverse without life than with life. But what about the rare universes that actually do contain life?
Well, just like you wouldn’t expect a lottery winner to win twice, the odds against life evolving a second time in the same universe would be incredibly low. It would happen in some universes, of course, but in the vast majority of “life” universes, you’d expect that life to be alone.
Without the multiverse, it would take a major conspiracy of nature to explain how we might possibly be alone in the universe. The cosmic coin would have to be insanely biased.
The multiverse allows us to account for our existence even if the odds of life evolving are as close to zero as makes a difference — and it may be one of the only ways of doing so.
When you assume…
Some die-hards will rightly point out that I’ve made a few assumptions. Among them:
- I assumed that the universe is finite (i.e. that there aren’t an infinite number of planets). If that’s not the case, the universe would have an infinite number of planets to “flip its coin on”, if you will.
- I assumed that our universe wasn’t designed by an intelligent creator, who fine-tuned it just for us.
- I didn’t talk about the possibility that we straight-up live in a simulation.
These are all fair criticisms, and worthwhile possibilities to consider.
And maybe there’s a universe where I managed to address each of them in this post.
But it’s not this one.
My new book, Quantum Physics Made Me Do It, is now available at fine bookstores across the multiverse! You can also find it on Amazon here (Canada), here (U.S.) and here (U.K.).
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