What is the Big Bang?

by Carson

Although we don’t yet know how the Universe started, the Big Bang is the best and the most widely accepted explanation. Find out what the Big Bang is and how it works in this article.

How Does the Big Bang Work?

In the Big Bang theory, around 13.8 billion years ago, the Universe was a singularity (i.e., a space so small that it has infinite density). Then, the Universe suddenly undergoes the Big Bang, significantly increasing its size and cooling down in a fraction of a second. This process has continued until today, as seen by the fact that the Universe is still expanding.

At first, the four fundamental forces (gravity, the weak nuclear force, the strong nuclear force, and the electromagnetic force) are joined together as one force. However, almost instantly, gravity becomes its own force. The strong nuclear force, the weak nuclear force, and the electromagnetic force also did this in a fraction of a second, meaning that the four forces are now separate.

In the first 380000 years of the Universe, it was still so hot (i.e., the particles move so fast) that they could not settle down as atoms. The force that puts electrons and protons together simply could not overpower the heat among the particles. It was until 380000 years after the birth of the Universe that electrons, neutrons, and protons started settling down as atoms, enabling photons to pass through them.

Why is the Big Bang the Leading Theory about How the Universe Started?

As far back as the 1920s, astronomers have already noticed that galaxies are speeding away from each other. Moreover, the farther the galaxy is from Earth, the faster it is escaping from our point of view. The phenomenon is so widespread and ubiquitous that it led scientists to think that the Universe is expanding. If it is truly expanding all the time, the Universe must, at one point, be infinitely small and infinitely dense (i.e., it was a singularity).

As of today, there is not much scientific evidence for objecting the Big Bang, so it remains the leading theory about how the Universe started. Many other theories are based on the Big Bang despite the theory itself being unproven.

How About the Big Bounce?

The Big Bounce theory is an extension of the Big Bang theory. That means that Universe expands after the Big Bang, then halts and shrinks back into a singularity, after which the next Big Bang occurs, repeating the cycle. If this theory is true, our own Universe is just one of infinitely many of them that has existed in the past and will exist in the future.

Unfortunately, we cannot learn whether the Universe is just one of an infinite series of universes through backtracking. Instead, we have to look into the future to obtain whether the Universe’s expansion will eventually stop and be outrun by gravity. However, it seems not very possible because the expansion of the Universe is currently accelerating due to dark matter and dark energy.


In this article, we discussed the leading theory of the formation of the Universe, which is the Big Bang. It is also mentioned how the Big Bang theory was discovered, and an extension of this theory theorizes the existence of a Big Bounce. If you want to learn more about these, please visit the webpages in the references below.

References and Credits

  1. Elizabeth Howell Andrew May. (2022, January 10). What Is the Big Bang Theory? Retrieved February 18, 2022, from https://www.space.com/25126-big-bang-theory.html
  2. Michael Greshko, National Geographic Staff, (2017, January 17). Origins of the universe, explained. Retrieved February 18, 2022, from https://www.nationalgeographic.com/science/article/origins-of-the-universe
  3. Paul Sutter. (2020, April 21). What happened before the Big Bang? Retrieved February 18, 2022, from https://www.space.com/what-came-before-big-bang.html

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