You've probably heard of “The Big Bang” which is the foundation of our existing universe, but how do we know there was a BIG BANG?
The Big Bang theory states that the universe has expanded to its current state from an infinitely dense and incredibly hot point called, “singularity.” However, the universe didn’t explode with a BANG as the name of the theory portrays. The start of the cosmos was more likely just an incredibly fast expansion. Within the first second of the big bang, the temperature reached about 10 billion 10,000,000,000 F or 5,550,000,000 C.
At this point the universe consisted of a sea of fundamental particles like protons and electrons. These electrons would have been free at this time and would have scattered light is all direction causing the universe to be opaque. But it wasn’t until about 380,000 years after the big bang that these free electrons were captured by nuclei. These formed the first neutral atom which allowed the universe to become transparent. The initial light which is also known as “Cosmic Microwave Background” is still visible today.
What made us believe the Big Bang is the start?
Throughout these billion years, the universe began to form areas of higher density who’s gravitational forces began to clump matter into nebulous stars and galaxies.
How are we so confident about the events happened in the past?
These events are predicted of the evidence we have. Various scientists have put multiple pieces of puzzles together to support the big bang theory. There are multiple strands of evidence to support the origin of our universe. Here are the top 3
1. Redshift of Galaxies
Back in 1912, Vesto Slipher used the Redshift of galaxies to calculate the speed and the direction of galaxies. He determined that most of the galaxies are moving away from us. At that time, however, Slipher thought that these were just a cluster of stars within our Milky Way.
Over a decade later, Edwin Hubble determined that the cluster of stars were in fact other galaxies outside our Milky Way, he determined this by using variable stars. These star pulsate and with the help of the intensity of the star, the distance was measured. So if all the galaxies in the universe are moving away from each other, back in time when they were closer or little more behind, they were at the same point? Run the clock forward and we have the Big Bang.
2. Abundance of Elements
Studies prove that at a very beginning, the universe was similar to a Star. That means soon after the big bang, hydrogen was essentially the only element in the universe. However, due to extremely high temperature and pressure, the fusion lead hydrogen atoms to helium and so on. This is known as “The Big Bang Nucleosynthesis”. Everything in the universe was a lot more compact.
3. Cosmic Microwave Background Radiation CMBR)
Back in the 1960’s Robert Wilson and Arno Penzias were performing experiments with Radio telescope and they noticed something weird. No matter where the direct the telescope or what time of the day it was, they would always detect a background radio emission. They soon figured that it was the enormous amount of radiation that had been previously theorized as being released by the big bang. This was the afterglow of the big bang. After billions of years this radiation was moving away from us at such high-speed that it shifted from visible light to microwave cosmic radiation.