I have recently come across the YouTube Channel Veritasium and watched the video about the possible existence of parallel universes, available at https://www.youtube.com/watch?v=kTXTPe3wahc. This video talks about quantum mechanics' randomness and its implied potential evidence of multiverses, which sparked my interest in exploring where our knowledge of physics and the universe currently stands.

Physics has been relatively straightforward until the appearance of the theory of relativity, introduced by Albert Einstein. As opposed to classical physics and the hypothetical element aether, this theory has overthrown the commonly-acknowledged "seeing is believing" scientific method. From the aspects of Newton's laws of motion, high-speed particles should also follow the F = m a formula, implying that objects can accelerate forever as long as there is an external force exerted upon them. This law later contradicts the fact that the speed of light is the hard speed limit in this universe's absolute-coordinated transporting medium — aether, and limits an object with mass to accelerate above the speed of light. However, the Michelson-Morley experiment, conducted in 1887 at the present-day Case Western Reserve University, found that the speed of light is relative to observation and disproves aether's existence.

Physics has only gotten even weirder with the introduction of quantum mechanics. Even Einstein himself does not fully accept quantum randomness and unpredictability, having once said, "God doesn't play dice with the universe." The reason behind the randomness of quantum particles is still unknown. It is strange to learn that electron beams act like light and form wave patterns when passed through a gap. It is even more peculiar to know that one single radioactive atom could decay at random times. Yet, on a macro scale, we can generalize these spontaneous decays into 'half-lives.' How do these atoms know to coordinate with each other to decay half of themselves during this period?

Some have therefore concluded that the randomness we observe from quantum mechanics is a product of a multiverse splitting into infinite separate timelines every time a random phenomenon occurs. On one timeline, a specific particle might have decayed and propagated that effect into its universe. On another timeline, the same particle might stay stable, causing a different universe to happen. These two timelines will forever diverge and go about on their paths, while infinitely creating more timelines on the way.

Although not scientifically proven to be accurate models of describing our universe, these proposals on the existence of multiverses provide a potential claim to eliminate the uncertainties in quantum mechanics. I have personally approached this problem with the idea of conservation of energy. Among the various physical properties in the universe that we have defined for measuring energy levels, there is one property — entropy — that stands out from the others because of the impossibility of its decrease throughout time according to the second law of thermodynamics.

With the constant increase of entropy in the universe, we are losing a certain kind of potential energy throughout time. Some cosmic theory suggests that with the continuous increase in entropy, the universe will eventually reach the heat death state. Once the universe enters this state, there will be no more usable energy for the universe to increase entropy. But where did this usable energy go, and how did it just irreversibly vanish from our universe? My take is that the multiverse theory would be the backbone to support the eventual heat death of the universe in that all the usable energy created during the big bang dissipates into creating different universes and timelines. These finite amounts of energy are split and diluted into different timelines during this process. While humans cannot confirm that these infinite splits happen at all in our 4-D world, we can observe an increase in entropy in our timeline. These splits, in theory, should happen every time we observe random behavior. With the Schrödinger's cat thought experiment, we can illustrate the quantum state when the cat is both alive and dead as having a higher energy state. After observing the cat, the quantum state collapses and loses energy, causing the entropy to increase. Every time this collapse happens, a separate timeline appears, each having half of the original quantum state's energy before collapsing. In this case, our loss of information in the cat's quantum state contributed to the timeline split, and in each timeline, we observe an increase in entropy.

Aside from entropy, the multiverse model may also imply that humanity's root lands on the only timeline that follows the physics defined by ourselves. Due to the probability of us falling into our timeline, our physics laws may only work in our timeline universe and not others. This multiverse model also raises another more philosophical question of whether our lives are predetermined or free-willed. Are all our cognitive decisions solely based on our current environmental circumstances, or does randomness more or less fuel them? Would we always make the same mistakes even though we can finally travel back to the past? Or would reverting ourselves to a moment in the past diverge us into another different timeline? It is interesting to see where our only timeline would take us into the future, but it would be even more interesting to know that the branches our timeline created were also part of it.