The Big Bang Theory is the most popular and widely accepted theory about how the universe began. It states that the universe began as a single point, infinitely hot and dense, which started to expand and is known as a singularity. At first, it expanded at extreme, immeasurable speeds but then slowed down as time went on- and is still expanding for the past 13.7 billion years. [1]
ERAS
- The Planck Era – This lasted 10-43 seconds immediately after the big bang, when the universe was made of pure energy. It is believed that the 4 basic forces of the universe [gravity, nuclear strong, nuclear weak, and electromagnetic] were acting as one. The stage is named after Max Planck and the universe was facing extreme temperatures during it (the temperature is said to be around 1034 K)
[Fun Fact: The Planck era is so short that modern technology can’t measure its length. Current physical theories can’t describe timescales shorter than the Planck time, which is the time it takes light to travel one Planck length in a vacuum, or about 5.39×10−44 seconds.] [2] [3] - GUT (Grand Unified Theory) Era – Lasted between 10-43 s to 10-38 s , and it is believed that the universe cooled to the point ‘the nuclear strong force began to freeze out, leaving three fundamental forces: gravity, the strong force, and the still combined electroweak force.’ [2] This obviously released a large amount of energy, causing a rapid “inflation.”
[Our universe grew from the size of an atomic nucleus to around the size of our solar system in about 10-36 s]
- Electroweak Era – 10-32 to 10-10 seconds after the Big Bang, the temperature was still around 1015K and the nuclear and electromagnetic forces were still combined, but towards the end, the temperature lowered below 1015K and the forces become distinct. [2]
- Particle Era – The universe was still too hot and excessively energetic 10-10 to 10-3 seconds after the big bang for any physical substances to develop. However, the fundamental forces were carried by the subatomic W, Z, and Higgs particles. [4]
- Era of Nucleosynthesis – A period of around 20 minutes into the Big Bang theory when nucleons in the primordial plasma cooled enough to combine into light nuclei such as that of the nuclei of deuterium, an isotope of hydrogen. [5] However, no element heavier than beryllium could be made.
- Era of Nuclei – Nuclear reactions couldn’t occur until about 3 minutes after the Big Bang. The temperature dropped too much at this point for them to continue. About 300,000–500,000 years after the beginning, the temperature was still high enough to retain all the atoms ionised (electrons free from the nuclei). [6]
- Era of Atoms – Between 380,000 and 1 billion years following the Big Bang, matter developed into the astounding diversity we are familiar with during this incredibly extended Period of Atoms. Due to gravity, the stable atoms of helium and hydrogen gradually drifted together in patches.[5]
- Era of Galaxies – The era of galaxies began about 1 billion years after the Big Bang and continues to the present day, which is 13.82 billion years after the Big Bang. Stars started to pull towards one another during this period, forming clusters that eventually gave rise to galaxies.
Evidence for the Big Bang
One of the main pieces of evidence for the Big Bang is the doppler effect. The Doppler effect is the change in frequency of light, sound, or other waves as they move towards or away from one another, depending on the position of the source and the observer. When waves from a source move in the direction of an observer, they become compressed.
The Doppler red-shift of light observed from distant stars and galaxies gives evidence that the expansion of the universe indicates its departure from a centre point. The Big Bang theory is made possible by the fact that all matter travels away from the site of origin following a “bang.” [7]
Works Cited
[1] Howell, Elizabeth, and Andrew May. “What Is the Big Bang Theory?” Space.com, 27 July 2023, http://www.space.com/25126-big-bang-theory.html.
[2] Gary, Dale. “Astronomy Lecture Number 26.” Web.njit.edu, web.njit.edu/~gary/202/Lecture26.html.
[3] Odenwald, Sten. “The Planck Era: Imagining Our Infant Universe.” Astronomy Magazine, 21 Apr. 2022, http://www.astronomy.com/science/the-planck-era-imagining-our-infant-universe/.
[4] Muro, Trisha. “Cosmic Timeline: What’s Happened since the Big Bang.” Science News Explores, 20 Oct. 2022, http://www.snexplores.org/article/what-happened-since-big-bang-physics-universe-cosmic-timeline.
[5] Office of Science. “DOE Explains…Nucleosynthesis.” Energy.gov, 2024, http://www.energy.gov/science/doe-explainsnucleosynthesis.
[6] “Era of Nuclei.” Arizona.edu, 2024, ircamera.as.arizona.edu/NatSci102/NatSci/lectures/eranuclei.htm.
[7] Newcomer Academy High School. “The Birth of the Universe” Newcomer Academy High School Visualization One. 30 Aug. 2013.
About the Author
As a young student navigating the exciting world of STEM, I’m fueled by a passion for science, art, and music and am aspiring to become an astrophysicist in the future. As a mere 15 year old girl, my travels across Asia, Europe and Africa have already exposed me to diverse cultures and sparked a curiosity that I translate into creative problem-solving.
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