Imagine another universe where every decision you made was an alternate reality. Instead of turning right the day you got into an accident, you turned left, avoiding it.
While it may seem more fiction than science, it’s long been theorized that our universe is one of many; a collection parallel universes called a multiverse. But how can there be another universe — let alone many — where another you exists?
There are varying beliefs about parallel universes and multiverses.
One is that if our universe is infinite, there are only so many ways that matter within it can rearrange itself. So, eventually, matter repeats itself. This could create another universe, and yet another, and another.
Another, similar theory is that in the creation of multiple universes there are other Earths, other yous. But in each, you have made different decisions, leading to another you but with another life (using this theory also means that there is likely an exact copy of you). The most recent example in cinema is the new Star Trek movies.
(There are also differing multiverse theories, including one where another universe is the opposite of ours, like one where there is no matter, but antimatter.)
This idea of multiverses is put forth in theoretical physics, specifically that dealing with string theory, a branch of physics that unifies Einstein’s general theory of relativity (which deals with the very large) and quantum mechanics (which deals with the very small). In string theory there are at least 10 different dimensions (there are also different types of string theories).
“The Big Bang giving birth to our universe is likely not a one-time event. Instead the fuel not only generates our Big Bang, but it would also generate countless other Big Bangs, each giving rise to its own separate universe with our universe becoming but one bubble in a grand cosmic bubble bath of universes,” said renowned physicist Brian Greene in a 2012 TED Talk.
WATCH: Brian Greene explains the idea of a multiverse
In this theory, each universe has an extra dimension with other physical qualities.
You’ve likely heard reference to Schrödinger’s Cat. In this thought experiment, a cat is put into a box with poison, radioactive material, a Geiger counter (measuring radiation) and a hammer. If any radiation is detected by the Geiger counter, the hammer will release, poisoning the cat. So, until you opened the box, the cat was both alive and dead. While people believe that Schrödinger’s believed the cat was both alive and dead, he didn’t. Instead, he disbelieved that things existed in multiple states at the same time.
WATCH: Understanding Schrödinger’s Cat
However, in quantum mechanics, the cat being both alive and dead is entirely possible. That this is so, means that there can be multiple universes and multiple worlds.
Thinking of these kinds of multiverses, parallel universes and the idea of many “yous” out there is enough to spin your head. And yes, it is all theoretical, but it is based on mathematics.
“It is strange to imagine other realms, separate from ours, most with fundamentally different features that would rightly be called universes of their own,” said Greene.
Searching for evidence of parallel universes
If there are multiple universes out there, theory predicts these universes can collide or even overlap. Physicists are actively searching for evidence, looking for signatures — hot or cold spots — in the cosmic background radiation (CMB), radiation left over from 380,000 years after the Big Bang created our universe. We have proof of this radiation, captured by multiple satellites over the past 20 years.
In a paper published last November, one scientist claimed to have found evidence of another universe interacting with our own.
Using the European Space Agency’s Planck Telescope, cosmologist Ranga-Ram Chary compared two images from Planck: one of the CMB and another of the night sky. What he found was an area that is 4,500 times brighter than what our theory predicts it should be. This, he says, is another universe leaking into our own.
Though Chary believes that another universe is a possible explanation, he does go on to say that further research is needed to ensure this is not something else interfering with the measurements.
While thinking about multiple dimensions, multiple universes, multiple versions of yourself, antimatter and all the rest might seem like science fiction, one day, we may have concrete proof that all these things exist, just in the same way that the idea of other planets seemed foreign at one time.
And, if you still don’t have that dream job, favourite car, or are still looking for your soulmate, take heart: somewhere out there, there’s a version of you where you might have it all.