Hi I’m Marley, the astronomer here at the Space Centre. Our theme this month is the multiverse which is an idea that is having a resurgence in pop culture right now. Entertainment media associated with the Marvel Cinematic Universe (MCU), and the film Everything Everywhere All At Once are some recent examples that have brought the multiverse back into pop culture in the past few years. But what are these projects actually talking about when they mean the multiverse? And is there a scientific basis for it?
When scientists discuss the multiverse, they are referring to the idea that beyond our observable universe, many other universes may exist. What those universes look like, and how they came to be is still unknown, but there are currently three multiverse theories in physics. I’m going to discuss the one that we see used in most shows, films, and other media that use the multiverse as a plot device: the Many-Worlds Interpretation of quantum mechanics (MWI).
In quantum mechanics, things are described using a wave function. The wave function is an equation that can tell you the probability of measuring a certain quantity at a certain time in a certain space. It is often explained in the context of trying to locate an electron. The wave function will tell you the probability of finding an electron at that point in space. If you were to check to see where the electron was, and measured it, then the wave function collapses. The electron is found to be in one of the places, and it does not exist anywhere else. The probability of the electron being found is 100% – in the location it was found in. In the MWI, this is applied to the entire universe. There is a universal wave function, which tells you the probability of where every particle in the Universe will be at a particular moment of time. But when a measurement is made, it does not collapse. The particle is found in one spot, but it does not stop existing in all the other places. Instead, there is a universe for each place it could be. To go back to our electron, even if you measured it to be in one location, there is another universe where it is in a different place. Think alternate realities.
Alternate realities serve to establish the multiverse plot that many science fiction stories are using when telling their stories. A key plot point is changed, and the story explores that other possibility. This is the basis of the What If…? Marvel television and comic series. These different universes originate due to points of “divergences”. An example of a divergence is an event that can have different outcomes which then causes different universes, one for each outcome. For example “our universe”, where superheroes don’t exist and Marvel characters are only in books and comics, is given the designation of Earth-1218 in Marvel. In the main MCU, the universe where Peter Parker gets bitten by a radioactive spider, is designated as Earth-616. There exists a universe where he didn’t get bitten and someone else did. In the Earth-616 universe, Uncle Ben died. There is also a universe where he didn’t.
Of course, scientists have no proof that there is any other universe outside of our own. The multiverse as an idea is entirely theoretical, which makes it difficult for me to give you any hands on activities to try. If you’re up for it, you can check out the various readings and videos below. As a fun thought experiment, keep track of how many choices you make in a day. How many alternate universes did you create?
I said that there were three physics theories that could explain how a multiverse would form. Check out this video by Paul Sutter where he explains a theory known as chaotic or eternal inflation. Sutter is an astrophysicist and research professor at the Institute for Advanced Computational Science at SUNY Stony Brook. He also has a podcast called Ask a Spaceman!
This TEDx talk by Delia Perlov goes into her research interest on the eternal inflation theory of the multiverse. Check it out if you want to know more. Perlov is an instructor in the physics and astronomy department at Tufts University.
Want to hear about the multiverse with a dash of string theory? Check out Brian Greene’s TED talk here. Greene is a theoretical physicist and is currently a professor of physics and mathematics at Columbia University.