You've probably read about how the Universe is expanding, and has been expanding since the beginning of time. Over the course of 13.8 billion years or so, it's stretched from the size of a billionth of a proton to the vast, unknowable expanse it is today. In fact, recent research suggests that it's actually expanding faster than our current laws of physics can explain, and that's kind of a problem. 

But all of that aside, whenever someone mentions our expanding Universe, we get a big, fat (turtle-surfing) elephant in the room. Because if the Universe is expanding, what exactly is it expanding into?

As Fraser Cain from Universe Today explains, one possibility is that it's expanding into an unfathomable cosmic void called the multiverse, which harbours not just our own Universe, but a multitude of parallel universes. We kinda want this to be the right answer, because if parallel universes really do exist, shit's about to get so weird.

As the video above explains, the laws of physics as we know them wouldn't necessarily apply in other universes. Things are fundamental to us and everything we know, such as the pull of gravity or the binding strength of atoms, that simply would not exist in other universes.

"For each one of these basic constants, it's as if the laws of physics randomly rolled the dice, and came up with our Universe," says Cain. "Maybe in another universe, the force of gravity is repulsive, or green, or spawns unicorns."

For a universe to form with the right combination of physical laws to allow for life to evolve, it's a monkeys and typewriters situation - roll the dice an infinite number of times, and you'll eventually get it right.

So let's say there are multiple universes - what if our Universe actually expanded so close to a neighbouring universe, it bumped into it?

Turns out, signs of such a 'cosmic bruise' do exist, and scientists have been trying to explain them for decades. In fact, there's one region in our Universe that's so confounding, scientists have literally called it the Axis of Evil

According to Cain, there are a bunch of explanations that could explain the weirdness of the Axis of Evil more reliably than it being the site of a great 'meeting of the universes', but we can't throw that possibility out just yet. And if it really is the case, what's happening to the poor aliens living in the universe that we're so rudely overlapping?

I'll let the video above handle that one, but let's just say it's somewhere between whatever the average of seven and green is, and the sum of 26 and unicorn dreams. Thanks a lot, science.