The theory of relativity proposed by Albert Einstein over 100 years ago, along with quantum mechanics, was also shaped by his contributions. However, throughout his life, Albert Einstein was unable to achieve his long-desired goal of unifying these two theories into a greater framework known as “the unified field theory.”
Relativity and quantum mechanics are two foundational pillars of modern physics, governing the macroscopic and microscopic worlds, respectively. Yet, when scientists attempt to unify these two theories, they encounter contradictions that render them incompatible, suggesting that our universe operates under two distinct sets of theories: one for the macroscopic world and another for the microscopic world.
Relativity and quantum mechanics are the two foundations of modern physics. (Illustrative image).
However, the macroscopic world we inhabit is fundamentally composed of the basic particles from the microscopic realm. There is no clear boundary separating the micro and macro worlds, which means that both must be unified and explained through the same theoretical framework.
This represents the greatest challenge; regardless of how hard scientists try, it is difficult to integrate relativity (general relativity) with quantum mechanics.
From a macroscopic perspective, general relativity clearly describes the nature of gravity, positing that gravity does not truly exist but is rather a manifestation of the curvature of space and time. In other words, the curvature of spacetime is the essence of gravity.
Any object with mass can influence the structure of spacetime, with the effects of massive celestial bodies being even more pronounced. Just like a trampoline, if you stand on it, the surface will dip. If you then place a ball on the trampoline, it will roll towards the center along the depressed surface.
Of course, this is merely a conventional metaphor; in reality, spacetime does not curve in such a manner but curves towards the center of mass of the object.
At the same time, general relativity emphasizes that the structure of spacetime is smooth and continuous.
However, when we delve into the microscopic world, everything changes and must be explained by a different set of laws: quantum mechanics.
It is difficult to integrate relativity and quantum mechanics. (Illustrative image).
The quantum world is neither smooth nor continuous; everything there is uncertain and constitutes a chaotic realm that cannot be accurately described.
In the quantum world, space and time are distorted, lacking direction as we know it, with no concept of up, down, left, right, and even the notion of time does not exist. You can never be certain if you are here or there; in fact, you might be in two different places at once.
Even more perplexing is that there seemingly is no causal relationship in the quantum world. To use a metaphor from the macroscopic realm, it’s as if you decide to go to the United States tomorrow, but in reality, you arrived there the day before yesterday. In the quantum world, time is just as chaotic.
The quantum world is not a smooth world. (Illustrative image).
The core of quantum mechanics is uncertainty, where everything defies conventional logic. Once we observe the quantum world, the observed object becomes defined. In other words, before observation, the quantum world remains uncertain, and the act of observation causes it to transition from uncertainty to certainty.
For example, consider a scenario in the macroscopic world. Your mother is cooking in the kitchen while you are playing a game on your computer in your bedroom. Both events are certain.
However, according to the uncertainty interpretation of quantum mechanics, you might not be playing a game in your bedroom at all; you could be anywhere else, like on the moon. And when your mother wants to see (observe) whether you are in your bedroom, your position is defined, and you can only be in one place, which would indeed be your bedroom. But from a purely theoretical analysis, it’s genuinely possible that you are on the moon, though this possibility is exceedingly small and can be regarded as nearly zero.
Einstein also had to admit that no one truly understands quantum mechanics. (Illustrative image).
Don’t worry; you’re not alone in your confusion, as even the physics giant Albert Einstein had to acknowledge that no one truly understands quantum mechanics.
Einstein dedicated the latter half of his life to working diligently toward the goal of unifying general relativity and quantum mechanics, but even his lifelong efforts could not complete this challenging task.
Nevertheless, quantum mechanics has permeated our daily lives; the electronic products we frequently use, such as mobile phones, contain quantum mechanical technology within their chips.
The ongoing conflict between general relativity and quantum mechanics remains unresolved, indicating that deeper theories await exploration by scientists. Quantum gravity theories and string theory have been proposed in recent decades in an effort to unify general relativity and quantum mechanics. Unfortunately, string theory still largely exists in mathematical models and conjectures and is challenging to verify experimentally!
