What’s Outside the Universe?

A few hundred episodes ago, I answered the question, “What is the Universe Expanding Into?” The gist of the answer is that the Universe as we understand it, isn’t really expanding into anything.

If you go in any one direction long enough, you just return to your starting point. As the Universe expands, that journey takes longer, but there’s still nothing that it’s going into.

Okay, so, I need to put an asterisk on that answer, and then when you read the fine print it’d say something like, “unless we live in a multiverse”.

One of the super interesting and definitely way out there ideas is that our cosmos to actually just one universe in a vast multiverse. Each universe is sort of like a soap bubble embedded in the cosmic void of the multiverse, expanding from its own Big Bang.

And in each one of these universes, the laws of physics are completely different. There are actually a bunch of physical constants in the Universe, like the force of gravity or the binding strength of atoms. For each one of those basic constants, it’s as if the laws of physics randomly rolled the dice, and came up with our Universe – a place that’s almost, but not completely hostile to life.

So imagine all these different bubble universes popping up in this vast cosmic foam of the multiverse, and the laws of physics are different. Maybe in another universe, the force of gravity is repulsive, or green, or spawns unicorns.

In the vast majority of those universes, no life could ever form, but roll the dice an infinite number of times and you’ll eventually get the conditions for life.

Any lifeform capable of perceiving the Universe had to evolve into a universe capable of life.

Of course, this sounds like pseudo scientific mumbo jumbo, and next you’ll expect me to talk about chakras, astrology and channeling the spirit of Big Foot.

However, hang on a second, this might actually be science. If these bubble universes got close enough, there might be a way they could rub together, to interact in ways that were detectable from within the Universe.

In other words, we could look out into space and see a cosmic bruise, and know that’s where our universe is colliding with another one.

Well, have astronomers looked out into space, in search of some sign that our Universe is interacting with other universes? Indeed they have, and they’ve found something really strange.

When examining the Cosmic Microwave Background Radiation, the afterglow leftover from the Big Bang, astronomers have found a temperature fluctuations. These different temperatures, or anisotropies are regions where different densities of matter in the early Universe were scaled up to enormous scales by the ongoing expansion.

While most of these differences in temperature are explained by the current cosmological theories for the Universe, there’s one region that defies the theories. It’s so strange, the researchers who discovered it hilariously named it the “Axis of Evil” after something some president said.

Anyway, there are lots of ideas for what the Axis of Evil might be. Seriously, every single one of them is more reasonable and more likely than what I’m about to say.

But one really fascinating idea is that we’re seeing a region where our Universe is bumping into another universe, violating each other’s laws of physics.

So if this is the case, and astronomers are witnessing a universal interaction, what does this mean for the poor aliens who might be getting overlapped by the next universe over?

We have no idea, but imagine what might happen as the laws of physics from two completely different universes overlap. What is the average of 7 and green? Or 26 and unicorn dreams? Whatever it is, it can’t be good for the aliens and their continued healthy existence.

But don’t worry, that region is billions of light years away, and it’s probably not another universe anyway, we just need better observations.

We covered this topic in great detail in episode 408 of Astronomy Cast, so if you want hear more from Dr. Pamela Gay, click here and watch the show. You’ll especially enjoy watching me pick up the shattered pieces of my brain as I try to wrap my head around this mind bending concept.