Many Worlds: The Multiverse is Real?

Written By: Kesavan Rangarajan

Quantum physics is a rather obscure field. In one’s normal life, most things are in one state at a time. For example, if a ball were to be kicked its position and velocity change over time; however, the ball is always in one state at a given time. In quantum physics, however, particles are in multiple states at the same time. Instead of the ball being at one position and one velocity, it's at multiple positions and multiple velocities at the same time. This superposition is due to the fact that quantum particles act like waves. Superposition is strange, but it gets even more peculiar. When a quantum particle is measured, it loses its superposition and is measured to be in a specific state. This collapses the wave function of the particle into a single point. When the wave function collapses, the outcome measured can be any of the points inside of the wave. This discovery introduced probability into our understanding of the universe.

Now you may have heard of Schrodinger’s cat thought experiment, where a cat is placed in a box, victim to a radioactive atom. Normally, you would say that the cat is either dead or alive, and you would find the answer when you open the box. However, when thinking of this with quantum mechanics, the cat should be perceived as both dead AND alive, until the box is opened. Schrodinger’s thought experiment parallels how particles are perceived on the quantum level.

Schrodinger's experiment teaches us the three main principles of quantum physics, superposition, entanglement, and measurement. Superposition is simply seen as the wave function of a particle, as a wave is spread out, and a superposition is a combination of multiple values. Entanglement, however, states that when two particles interact, instead of being described as two different wave functions, they are now one singular wave function. This means that when one entangled particle is measured, the wave function collapses, and we can know information about the other particles. Since entanglement turns multiple particles into one wave function, that means that the universe has its own wave function. Lastly, measurement is simply the act of measuring the states of the quantum particles, right? Wrong! We are also made up of the same quantum particles, so, when measuring a system, we get entangled with it too.

Now back to Schrodinger’s cat. Instead of seeing that cat as either dead or alive, since we become entangled, we are also in that superposition. Therefore, we see the cat as both dead and alive at the same time. But you’ve probably never seen a cat as both dead and alive, have you? Well, that’s because those scenarios occur in separate worlds. When a quantum particle gets entangled with the environment around it, it undergoes environmental decoherence, which branches the wave function of the universe, splitting the universe into two different versions, one where the cat is dead, and one where the cat is alive. This is called the Many-Worlds theory, and it means that the rate of the splitting of the wave function of the universe could be infinite.

Works Cited

Parallel Worlds Probably Exist. Here’s Why, Veritasium, 6 Mar. 2020, https://www.youtube.com/watch?v=kTXTPe3wahc. Accessed 29 Sept. 2023.