How Did the Universe Begin? And How Will the Universe End?

NASA/WMAP Science Team - via Wikimedia Commons.

The principle theory surrounding the origin of our universe is the Big Bang Theory (most of you should know this, as it is one of the most well-known scientific theories). The Big Bang Theory states that our universe originated from an exceptionally small point of infinite temperature and density around 13.8 billion years ago. From what is considered the Singularity (the small ball that contained all the matter of the universe), this small universe expanded extremely rapidly (apparently, though not actually much, much faster than the speed of light). 

        While there is strong mathematical evidence supporting the Big Bang Theory, we also have some strong supporting physical evidence. The best physical evidence substantiating the Big Bang Theory is the Cosmic Microwave Background (CMB). The CMB is a relatively uniform background of radio waves that fill the observable universe. The radio waves from the CMB are remnants from the moment the universe became cool enough to become transparent to light and electromagnetic radiation. These radio waves are emitted at near-complete uniformity amongst the entire universe, with some slight deviations in density (around 1 part in every 100,000). 

        There are a few theories surrounding the origin of the origin of the universe, but one theory stands out the most. The strongest theory surrounding the cause of the Big Bang was that there was no cause. As we look back to the Big Bang, the physics of the universe just break down. Not only the physics, but even the dimensional planes of the universe itself also break down. Thus, in that moment, not only does the universe have no length, width, and height, but also it doesn’t have time. Do you see where I am coming from here? Without time, events have neither a beginning nor an end. Therefore, a “cause” for the beginning of the universe simply doesn’t make sense. This is incredibly conflicting for our pattern-sensing minds; we always believe that every event is caused by another event (it is considered the universal law of cause and effect), but quantum physics, of course, says otherwise.

        The CMB will also be very important for the next question we will ask today. Now we ask, will the universe end? And if so, how will it end?

        The basis of the possible end of the universe is primarily based upon the rate of expansion of the universe. Edwin Hubble first discovered in 1929 that the universe was expanding, and that it was expanding at an increasing rate. This current rate is around 73 kilometers per second per megaparsec. This means that, on average, a galaxy 3.26 million light years (or a megaparsec) distant would be traveling away at around 73 km/second. If you double that to 6.52 million light years (2 megaparsecs), you will observe an increased rate of expansion that is now 146 km/second. This rate will continue to increase as distance increases.

        As conveyed by Stephen Hawking in A Brief History of Time, there are three models predicting this supposed ‘end’ of the universe. All three of these models are based on the relationship between the rate of expansion of the universe and the gravity of the mass of the universe. 

        The first of these models predicts that the rate of expansion of the universe is too slow to be resistant to the gravitational attraction of the matter in the universe, and the expansion slows, stops, and then reverses. This is frequently referred to as the ‘Big Crunch.’ The interesting thing about this theory is that the universe will eventually crunch back to a singularity; perhaps, then, the universe is a recurring multiverse that periodically reverses from singularity to expanding universe to contracting universe, and then back to the singularity, and so on.

        The second model predicts a universe that is not only expanding fast, but accelerating, to the point where the gravitational binding of the matter in the universe cannot slow down the acceleration of the universe. The universe will thus continue to expand and accelerate until infinity. This model is most-widely accepted in the scientific community today, in part because the universe is not only expanding fast, but its rate of expansion is also increasing. The current rate of expansion of the universe is 73-74 kilometers per second per megaparsec, and this number has been observed to be increasing. While we may be wrong, this is the most-supported theory surrounding the ‘end’ of the universe. The reason for this acceleration is because of the mysterious energy astronomers and physicists call dark energy. Because energy is a property of the universe and is not weakened by the universe's expansion, it will only continue to fuel the accelerating expansion of the universe. 

        The third and final model predicts a universe that continues to expand but where this expansion is slowed by the gravitational pull of the galaxies. The universe will continue to expand in this model forever, but its rate of expansion will grow slower and slower over time. The slowing of this expansion reminds me of exponential decay in which the number continuously decreases but can never reach zero. That same concept is evident in this model. This same model is possible and may produce a similar outcome to the second model depending on what time the expansion of the universe slows to a meager and minute point.

        Such is the main conjecture of the scientific community surrounding the cosmology of our universe. I personally side with a universe borne out of a singularity that didn’t contain any dimensions simply because it is the most well proven of all these theories. Yet, by no means do I have the insight or the grasp on cosmology to choose a side with legitimate substantiation; rather, I rely entirely upon what is accepted in the scientific community, and I side with whatever that community accepts.

If you have any questions, comments, or corrections, please comment on this post or email learningbywilliam@gmail.com with your concerns. Thank you.

References

The Big Bang. (n.d.). Retrieved from https://science.nasa.gov/astrophysics/focus-areas/what-powered-the-big-bang

Dark Energy, Dark Matter. (n.d.). Retrieved from https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy

Gunn, D. A. (2020, April 21). What caused the Big Bang? Retrieved from https://www.sciencefocus.com/space/what-caused-the-big-bang/

Hawking, S., & Miller, R. (1998). A Brief History of Time. Bantam Books.

How Can the Universe Expand Faster Than Light? - Ask a Spaceman! (2016, May 04). Retrieved from https://www.youtube.com/watch?v=_pobcjRAX3o

Howell, E., & May, A. (2022, January 10). What is the Big Bang Theory? Retrieved from https://www.space.com/25126-big-bang-theory.html

The Origins of the Universe: Inflation. (n.d.). Retrieved from http://www.ctc.cam.ac.uk/outreach/origins/inflation_zero.php

Strickland, J. (2021, February 22). How the Big Bang Theory Works. Retrieved from https://science.howstuffworks.com/dictionary/astronomy-terms/big-bang-theory

Williams, M. (2015, December 18). What is the Big Bang Theory? Retrieved from https://phys.org/news/2015-12-big-theory.html

Zyga, L. (2015, February 09). No Big Bang? Quantum equation predicts universe has no beginning. Retrieved from https://phys.org/news/2015-02-big-quantum-equation-universe.html