What is the Multiverse? Is this science fiction or does it really exist?
Whether you need a new villain or an old Spider-Man, your sci-fi movie will sound more scientifically believable if you use the word multiverse. The Marvel Multiverse puts several different versions of our universe “out there” somewhere. In these films, with the right mix of technology, magic and imagination, travel between these universes is possible.
For example (spoilers!), in Spider-Man: No Coming Home, we discover that there are other universes and other Earths, some of which have their own local Spider-Man. In the world of film, magic is possible.
This magic, thanks to a failed spell by superhero Dr. Strange, transports some of the other Spider-Men to our universe, along with a few supervillains.
In Doctor Strange in the Multiverse of Madness (in theaters now), universe-on-universe buffoonery threatens a “profanation of reality.”
So which of these ideas has Marvel based on science, and which are pure fiction?
Multiverse lite: a very large universe
Could there be other Earths? Could there be other people out there, who look a lot like us, on a planet that looks like ours? Scientifically, it’s possible, because we don’t know the real size of our universe.
We can see billions of light years into space, but we don’t know how much space is left out there beyond what we can see.
If there is more space out there, full of galaxies, stars and planets, then there is more and more chance that another Earth exists. Somewhere. With enough space and enough planets, any possibility becomes probable.
The fiction of the Marvel Multiverse stems from the ability to travel between these other lands. There’s a good reason Dr. Strange needs to use magic for this.
According to Albert Einstein, we cannot travel through space faster than light. And while more exotic ways of traveling the universe are scientifically possible – wormholes, for example – we don’t know how to make them, the universe doesn’t seem to make them naturally, and there’s no reason to think they would. connect us to another Earth rather than a random part of empty space.
So, almost certainly, if another Earth is somewhere out there, it’s incredibly far away, even for an astronomer.
Change the laws of nature
The Marvel Multiverse may seem wild, but from a science perspective, it’s actually too tame. Too normal. Too familiar. Here’s why.
The basic building blocks of our universe – protons and neutrons (and their quarks), electrons, light, etc. – are capable of creating amazing things, like human life. Your body is amazing: gathering energy, processing information, building mini-machines, self-repairing.
physicists discovered that the ability of the building blocks of our universe to create life forms is exceedingly rare. Just any old blocks won’t do.
If the electrons had been too heavy, or if the force that holds atomic nuclei together had been too weak, the matter of the universe wouldn’t even stick together, let alone do something as wonderful as a living cell. . Or, indeed, anything which one might call alive.
How did our universe get the right mix of ingredients? Maybe we have won the cosmic lottery. Perhaps, at scales much larger than what our telescopes can see, other parts of the universe have different building blocks.
Our universe is just one option – a particularly lucky one – among a multiverse of universes with losing tickets.
This is the scientific multiverse: not just more of our universe, but universes with different fundamental ingredients. Most are dead, but very, very rarely does the right combination for lifeforms show up.
The Marvel Multiverse, on the other hand, is just rearranging the familiar atoms and forces of our universe (plus a bit of magic). It is not enough.
Cosmic inflation and the Big Bang
How was our universe in the past? The evidence suggests that the universe was hotter, denser and smoother. This is called the Big Bang theory.
But was there a big Bang? Was there a time when the universe was infinitely hot, infinitely dense, and contained at a single point? Well, maybe. But we’re not sure, so scientists have explored a bunch of other options.
An idea, called cosmic inflation, says that in the first split second of the universe, it expanded extremely rapidly. If true, that would explain some things about why our universe expands exactly the way it does.
But how do you make a universe expand so quickly? The answer is a new type of energy field. It controls the first moments of the universe, causes rapid expansion, then hands over the reins to the most familiar forms of matter and energy: protons, neutrons, electrons, light, etc.
Cosmic inflation could create a multiverse. Here’s how. According to this idea, most of space expands, swells, doubles in size, from moment to moment. Spontaneously and randomly, in small islands, the new energy field converts its energy into ordinary matter with extremely high energies, releasing what we now consider a Big Bang.
If these high energies scramble and reset the basic properties of matter, then each island can be considered a new universe with different properties. We have created a multiverse.
So is there a multiverse?
In the cycle of the scientific method, the multiverse is in an exploratory phase. We have an idea that could explain some things, if it was true. That makes it worthy of our attention, but it’s still not quite scientific. We need to find more direct, more decisive evidence.
Something left over from the aftermath of the Multiverse Generator might help. A multiverse idea could also predict the winning numbers on our lottery ticket.
However, as Dr. Strange explains, “The multiverse is a concept we know awfully little about.”
Written by Luke Barnes, Lecturer in Physics, Western Sydney University.
This article was first published in The conversation.