Our Mathematical Universe: Four Kinds of Multiverse Max Tegmark

BY OLIVIA DANNER

In his book Our Mathematical Universe, Max Tegmark explores the math and physics behind our reality, both on the quantum and the cosmic level. A particular interest of his is the possibility of parallel universes, which he genuinely believes exist ― not what you’d expect from a scientist. He discusses four ‘levels’ of multiverse: levels I and II arise from the concept of cosmic inflation, level III is based in quantum mechanics, and level IV strays into more philosophical territory.

Tegmark’s argument for the Level I multiverse is that if space is expanding infinitely and uniformly ― which is the commonly accepted model of the universe ― then the same processes that spawned our universe must have also happened far, far away. Uniformity gives us that eventually, one of those universes must look identical to ours, up to a certain point where they diverge.

The Level II multiverse spawns from the same idea, but takes it a step further. It suggests that rather than all of the universes existing in the same massive space, they exist alongside each other and cannot ever interact with one another ― the boundaries between universes expand infinitely as well. This also suggests that during the creation of each of these universes, fluctuations of a quantum scale could result in changes to fundamental values, like the mass of an electron. This would, in turn, lead to changes to reality on a macroscopic scale: an alternate universe with different laws of physics.

The Level III multiverse is my personal favorite because I’ve now taken two semesters of quantum mechanics. You’ve probably heard of Schrödinger’s cat: a cat in a box with a poisonous gas triggered by a quantum event. Until you open the box, the cat is both alive and dead. This is a thought experiment describing quantum superposition of states. Because of the nature of quantum mechanics, if you observe a quantum event, it fundamentally changes the system by essentially destroying the other possible results. Tegmark discusses the possibility that this observation works differently than previously assumed, in a way that means that rather than a possibility being destroyed upon observation, it actually does occur ― we just can’t interact with that version of events.

Level IV doesn’t make a whole lot of sense to me so I won’t try and explain it, but it has to do with the concept of a mathematical structure and the idea that there are other possible ones. If you’re interested in learning more about it, it’s a fascinating read!