The possibility of many other universes existing besides our own might be mind-boggling and sound only as a wild scenario for sci-fi movies, but there are plenty of scientific theories out there that back up such a hypothesis. However, we must emphasize that just because doing the math indicates that we live in a Multiverse doesn’t automatically mean that it’s true. But there’s still a good chance that more than one single universe exists somewhere out there in the vastness of our physical reality.
To add insult to injury, there’s even a chance that each of the other universes has a copy of each and every one of us representing the outcome of different decisions that we’ve made. On a somewhat poetical note, the universe might not be willing to obey our own will, meaning that it will instantly create replicates of each and every action that we ever had the possibility to take. If that’s true, it means that in another universe, Joe Biden might be a rockstar with long black hair, while James Hetfield, the frontman of Metallica, might activate in Depeche Mode, for instance. The examples could continue forever, but you got the idea.
String theory refers to a theoretical framework that tries to describe the fundamental particles as one-dimensional “strings” rather than point particles. When it comes to certain versions of string theory, there are more spatial dimensions besides the usual three, and different vacuum states could result from the way these dimensions compactify. Each of the vacuum states could correspond to a different universe that’s part of a Multiverse.
What the inflationary theory states is that the early universe has been through an extremely fast expansion, even faster than the speed of light, starting a few short moments after the Big Bang. In other words, after the ‘bang’ itself, the universe started to inflate rapidly, and we see some aftermath of that inflation even today, although it took place 13.7 billion years ago. Nobody knows exactly why the Big Bang occurred in the first place, nor how the laws of nature began to exist. But let’s leave that aside for the moment.
The cosmic inflation theory was proposed to explain certain features of the cosmos, and it also allows for the possibility that different regions of space might have stopped inflating at different times. This led to the creation of new universes as giant “bubbles” and, therefore, the Multiverse formed.
Quantum Many-Worlds Interpretation
Each time a quantum event happens with multiple possible outcomes, the universe will split into different branches, each of them realizing one of the possible scenarios. It wasn’t long until these weird laws of the quantum realm made scientists believe that a Multiverse can form if all the possible outcomes of quantum events actually happen in parallel for different branches. As long as we’re all made of quantum particles, such as the planets, galaxies, stars, air, water, and everything else in the universe, why wouldn’t we all exist in other universes as well as copies and outcomes of different possible actions of ours? That seems like a pretty reasonable question once you get used to the odd laws of quantum mechanics.
Could we ever reach other universes?
One definition of other universes is that science could never allow us to ever travel to one of them. If other universes truly exist, they must be very well delimitated from our own universe. But there is a slight theoretical chance that humanity might travel to another universe of the Multiverse, if there are any. Wormholes represent the only theoretical way, although the scenario remains highly farfetched for multiple reasons.
Wormholes don’t occur naturally, which means that someone or something needs to build one for us. In fact, we’re not even sure that wormholes exist, as only the math indicates that they could be somewhere out there.
Creating a wormhole requires an extremely high amount of energy, higher than our planet was ever able to produce. In other words, we can’t make a wormhole, but perhaps some superintelligent alien civilization will make one for us someday, such as what happened in the sci-fi ‘Interstellar’ movie from 2014. Of course, we can’t even be sure that aliens exist, so there you go, another reason to lose faith in the wormhole scenario.
By definition, wormholes are nothing but hypothetical shortcuts through spacetime. While if they somehow exist, they could make us reach other remote regions of the universe, there’s also the possibility (again, only theoretical) that they can open a door for us to another universe. Perhaps the only hope is for scientists to find a way to generate an infinite amount of energy in the future to create a wormhole for us, but at this point, nobody knows how to do that.
Although it’s obvious to anyone at this point that the world can’t yet take the Multiverse scenario seriously, and not because it can be depressing, there are plenty of scientists out there who are very optimistic that we might indeed live in a universe that’s just one of many other universes in existence. Cristian Presura, a Romanian physicist who’s known for creating a smartwatch capable of measuring the pulse, even said that at this point, scientists are almost certain that there are many other universes out there, about 10 to 500 power. That’s more than the number of atoms in our observable universe.