Science Fiction & Fantasy




When Universes Collide

Once upon a time, in an age before civilization, before humanity, before the dinosaurs, even before the Big Bang, our universe…wasn’t. Nothing, nada. Void. It’s scary but true. Once upon a time, our universe didn’t exist, not even as a twinkle in God’s eye.

Now, you might say why bother talking about a time we can’t observe. You might say it’s pointless, unscientific. You might say a lot of such things, and guess what, you’d have a point. Because even for the greatest scientific minds in the world, any speculation about that time before time would be nothing more than an educated guess. Our universe, and all that is in it—including mass, energy and time—all began at the moment of the Big Bang, and we have no observational way of learning anything about what came before, or even what caused, that first moment, that first Bang, to start and to unfold into our present space-time continuum. This great unknown is perhaps one of the most annoying facets of physics and the ultimate unanswerable test question.

But we want to know. As scientists—as humans—we want to know everything, the how, the where, the why of it, and so finally answer the most fundamental questions of our universe’s origins.

Some of the greatest thinkers in the world—mathematicians, physicists, philosophers, clerics—have applied their minds to this question, all looking for answers that are consistent both with what we can observe and that also leave space for more. The scientific among them, the ones confining their thought experiments to the realms of science and logic, are guided in their search by one simple precept: the mediocrity principle.

The mediocrity principle states that we don’t live in a special time or a special place, that life on Earth depends on just a few basic molecules, and that those molecules probably also exist in other parts of the universe. Ergo: we’re not special.  But holding this belief means that any theory we come up with (for the void, for the Bang) must explain how we then came to arrive as a sentient species in a universe that, to all outward appearances, seems finely tuned for life.

But the more we learn about our universe, the more we realize that life actually wasn’t a foregone conclusion.

Consider gravity for a moment. We don’t know of any underlying reason that it must work as it does. It simply does.  But if gravity had been just a bit stronger, the universe would have collapsed down to black holes in the first mega millennia or so. And if gravity had been a bit weaker, stars might not have formed at all. Instead, gravity, for no required reason, is just right to sustain a universe with life. This fine-tuning is just one example of all the many fine tunings—from factors affecting molecular bonding to factors affecting electricity—that keep our universe chugging along. And the more we look at our universe, the more it actually does seem as if someone tweaked the preference knobs—the universal file settings if you will—over and over again until things were tuned just right for life.

But then we remember our one guiding principal: that we aren’t special, that we don’t live anywhere special.  That we are…mediocre.

So how do we reconcile these two conflicting ideas?

Well, actually, there are two scientific ways to cope with the fact of a finely tuned universe and the principle that our universe isn’t special.

The first is that we say that there could be, should be, must be some underlying physics that dictates a universe has to look like ours. It just is and that’s that.  This concept explains the fine-tuning by saying that the way things are is the only option. It’s a straightforward answer, and one that, happily for us, produces a single universe with a single set of physics. It doesn’t help us understand where we came from, sure, but it certainly makes the now a rather pleasant place to be.

And then there’s the alternative, where we conjecture that, instead of one universe, there could be an infinite number of universes out there, each one bubbling forth from some sort of quantum foam, forming with their own physics and their own set of functions and final preference values that may or may not support life. In this multi-verse scenario, our universe isn’t particularly special, just the result of throwing a handful of dice over and over and every once in a while ending up with Yahtzee.

There is at once something awesome about this idea and something terrifying. The concept of a multi-verse gives the question of origins a potential answer by making us just another fluctuation in an infinite series. And while infinites are uncomfortable, they are, at least, an answer.  But at the same time, it also opens up the idea of other places, other ages, other universes filled with people living other lives. The multi-verse concept makes anything possible because over infinite time, everything is probable. Everything.

Including universe collisions.

If you’ve ever watched a child blowing bubbles, you’ll know that most of the time, the bubbles burst. Every once in a while, however, they combine. And if our universe is just one of many in a free-floating, soap bubble-like multi-verse, there is a chance, a slim one, but a chance, that our universe and another could collapse in on each other, merging like two iridescent soap bubbles meeting in the wind.

We have no idea what would happen as a result. We might simply wink out—Poof! Gone!—Our entire universe ceasing to be in a single moment. Or perhaps the laws of physics as we know them might unravel, changing to take on characteristics from the new universe. If this happened we’d also likely cease to be: How could life survive if the laws that keep our planet together and our star burning suddenly changed? It’s also doubtful we could survive the effects these changes might have on our DNA. Luckily though, we probably wouldn’t even have time to realize we were going extinct.

According to the laws of our universe, nothing can travel faster than the speed of light. Assuming the merging universes keep that one rule (or replace it with a faster speed of light or instantaneous travel), then the changes would rush across our universe at the speed of light. We’d never see them coming, though, because just as an image of the stars tearing apart reached our eyes, the new laws of physics would be upon us, and we’d be torn apart as well.

Unless, of course, the merging universe brings with its slow roll of destruction a slower speed of light or some other strange physics. In this case, we might experience our own “Neverending Story” as we watch the stars wink out and a Great Nothing consume all we know, making way for something new to form and take its place.  Or we might get to watch, terrified, as everything around us transforms, including ourselves, if the propagation is slow enough, and perhaps suffering awfully as the physics ruling our body changes, with no child to dream us back again.

We don’t know how many universes came and went (or failed to come and go) before ours. We don’t know how many times life has (or hasn’t) experienced the merging of two universes. We don’t know many things. I don’t actually know if our universe will last long enough for you to read these words I’ve written. But for all that we don’t know, I feel safe in saying that, while anything is possible, it is, in fact, highly unlikely that our fragile human race will ever witness the merging of our universe with another.

After all, the exciting stuff always happens to someone else.

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Pamela L. Gay

Pamela GayDr. Pamela L. Gay is an astronomer, writer, and podcaster focused on using new media technologies to engage people in science and technology. You can learn more about astronomy each week through Want to do science? Help Pamela and other scientists through