The big bang is one of the interesting theories about the universe that modern cosmology can present. But, this is more than just an idea. It is a scientific theory because there is some strong evidence as for its base. For example, the cosmic microwave background is a kind of echo. For example, the ongoing expansion of the cosmos, the type origin of Big Bang, and the primordial elements like helium-3, helium-4, deuterium, and others. These things are real and scientists can calculate those elements by using this theory.

## Why Does The Big Bang Happen?

But, it does not mean there is no puzzle to solve at all. So, why does the Big Bang happen? What caused it to happen? Scientists cannot answer this simple question for many years. Therefore, they relied on the idea, saying that the universe formed spontaneously. Or, the presence of quantum fluctuations made Big Bang happened so the Universe was from nothing. Do not you think that this is plausible? We have heard many times about quantum mechanics, but of course, there should be something more. For example, we need something to back up this idea, the mathematical proof.

## The Quantum Fluctuations

Having the obsession to answer that question, Dongshan He and his buddies at the Wuhan Institute of Physics and Mathematics in China showed their first rigorous proof. These guys talked about the Big Bang that happened spontaneously since there were quantum fluctuations.

He provided the new proof based on the special set of solutions to a mathematical entity, called the Wheeler-DeWitt equation. It was in the first half of the 20th century, cosmologists attempted to combine the two pillars of quantum mechanics and general relativity, which were the modern physics so they could be more reasonable to describe the universe.

## Wheeler-DeWitt Equation

Then, it was in the 1960s we saw the breakthrough. John Wheeler and Bryce DeWitt, the physicists combined these incompatible ideas in the mathematical framework. We called it as the Wheeler-DeWitt equation. It was the new work of Dongshan and team as the attempt to explore the new solutions to this equation.

Heisenberg’s uncertainty principle became the basic line of their thinking. So, it was a small empty space to come into existence because of fluctuations. Physicists call this condition is the metastable false vacuum.

When this condition happens, there are only two options left. First, if the bubble of space does not expand, it disappears again. Second, if the bubble expands to a large size, then it creates a universe in a way that is irreversible.

Now, the question is does the Wheeler-DeWitt equation allow it? Dongshan and co proved that once a small true vacuum bubble is created, there is a big chance to expand exponentially. Here, they have a nice approach. They consider a spherical bubble is described by its radius. After that, they derive the equation that tells the rate at which the radius can expand. They even consider three scenarios for the geometry of the bubble. It can be closed, open, or flat.

## How The Universe Formed

At this point, they discover a solution that the bubble can expand exponentially. Therefore, it can reach a size that the universe can form and then the Big Bang happens. Also, it has an interesting corollary.

Cosmological constant becomes one important factor in models of the universe at this time. This term describes the energy density of the vacuum of space. Originally, Einstein introduced this idea in his 1917 general theory of relativity. But, this theory then abandoned after the Hubble’s discovery stated that the universe was expanding.

In the 1990s, most cosmologists argued that the cosmological constant was zero. But, recently, cosmologists found evidence that there is something that can accelerate the expansion of the universe. So, the cosmological constant is impossible to be zero.

## The Quantum Potential and Pilot-Wave Theory

Here, the cosmological constant has an important role in Dongshan and co’s new theory. They say that a quantity called the quantum potential has an important role of the cosmological constant in the new solutions. This argument came out from the idea we call it a pilot-wave theory. The man who developed this idea was David Bohm, a physicist back in the middle of the 20th century. From this theory, he reproduced all the conventional predictions of quantum mechanics that accept the additional term, called the quantum potential.

So, what is the effect of this theory? It makes quantum mechanics are deterministic. Scientists can use the quantum potential to work out things such as the actual position of the particle. Unfortunately, the mainstream physicists could not take this idea since the predictions are identical to the conventional version of the theory. There is no experimental way to tell them apart.

Finally, the quantum potential is a necessary part of a new mathematical derivation related to the origin of the universe is so much interesting. We hope scientists give Bohm’s ideas another spin.