In the field of modern physics, there are two stories that describe our universe. The first story suggests that the universe is fundamentally made of space-time, a continuous and stretchy fabric that has been expanding since the beginning of time. The second story suggests that the universe is fundamentally made of indivisible entities that cannot determine their position or timing.
Both stories have their merits and accurately describe the phenomena we observe. However, the main difference lies in the scales at which they apply. Albert Einstein’s theory of general relativity, which explains gravity, space, and time, governs massive objects and cosmic distances. On the other hand, quantum physics governs the behavior of tiny atomic and subatomic particles.
At the heart of the issue is the fact that both theories cannot simultaneously be true. This becomes particularly evident when considering the concept of the big bang, where the entire universe was compressed into an infinitely small point. In this scenario, a single theory that combines gravity and the quantum realm is required. Toby Wiseman, a theorist at Imperial College London, acknowledges this and states, “Why we’re here is the big question. It seems that quantum gravity is the only answer.”
Despite decades of research, however, the answer to quantum gravity remains elusive. Quantum gravity necessitates a reconciliation between the continuous and the indivisible, the predictable and the random. Many ideas have been proposed, but none have been able to fully incorporate all aspects of the problem. “We’re still no better off at understanding the beginning of space and time,” says Wiseman.
Most physicists tackling this challenge begin with quantum physics, using the widely-used framework of quantum field theory. This theory describes three out of the four fundamental forces of nature (electromagnetism, strong nuclear force, and weak nuclear force) by quantizing them as particles that carry these forces. However, this approach is not sufficient…
Insights:
1. The search for a theory of quantum gravity has been ongoing for many years but has not yet reached a definitive conclusion.
2. Quantum gravity is seen as the solution to understanding the beginnings of space and time, particularly in relation to the big bang.
3. Existing theories, such as quantum field theory, attempt to incorporate both quantum physics and gravity but have not been successful in fully explaining the phenomenon.
