What is The Big Bang Theory?

What is the Big Bang Theory?
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History of the Big Bang Theory


Before the Big Bang theory, the dominant theory of cosmology or the study of the universe was a steady-state model. The universe was estimated to be infinite in size and scope. Stars might be born and die, but others took their place.


In 1929, Edwin Hubble discovered that most of the universe was expanding and moving away from everything else. If everything is moving away from everything else, then it should be thought that everything was once closer together. The logical conclusion is that at some point, all matter started from a single point a few millimeters across before exploding outward. It was so hot that it consisted of only raw energy for hundreds of thousands of years before the matter could form. Whatever happened had to unleash an unfathomable force, since the universe is still expanding billions of years later. The theory he devised to explain what he found is called the Big Bang theory.

Theoretical Early History of the Universe

Theoretical Early History of the Universe


Between twelve and fifteen billion years ago, the universe was a single point of immensely dense, hot space. It exploded into the Big Bang. For a millionth of a second, the universe expanded incredibly fast from a sub-atomic or millimeter in size to the size of a golf ball. Protons and neutrons formed about three seconds after the Big Bang. Within minutes, hydrogen formed. It took a hundred thousand years or a few hundred thousand years for the universe to cool enough for a matter like molecules like deuterium to form and photos and light to be created.

Two hundred million years passed before gas clouds formed, nurseries for the first stars. About five billion years after the Big Bang, the universe started to slow its expansion as the first generation of stars lit up the sky. About six billion years after the Big Bang, it is believed that dark energy or dark matter started to speed up the universe’s expansion again.

Also Read: What if the Moon Disappeared?

Evidence for the Big Bang Theory

Evidence for the Big Bang Theory


The discovery of Cosmic Microwave Background Radiation further supports the Big Bang hypothesis. In 1965, the background radiation of the same frequency was discovered. Furthermore, the radiation levels were the same in all directions. The Cosmic Microwave Background Radiation is leftover from a period about 300,000 years after the big bang when the matter cooled and coalesced into electrons and photos and nuclei. The cosmic radiation they heard is the noise released by the conversion of hot matter into individual atoms and photons.


The mathematical models of the Big Bang predict specific ratios of different elements, with hydrogen being dominant. We see these element ratios today, with hydrogen still dominant while the amounts of helium and carbon rising as stars convert hydrogen into denser elements.

Further evidence is in Einstein’s theory of relativity. The mass of the universe, like all large masses, has a gravitational pull. He theorized that the universe would collapse on itself unless there was an unknown cosmological constant that kept it from collapsing in on itself. The Big Bang theory explains this contradiction; the force of the initial explosion is what is pushing the universe apart.

Einstein’s theory of relativity


Maps of the universe show the outer limits to reside in a sphere of about 14 billion light-years across. Like a soap bubble blown up, this structure fits with the model of an expanding sphere from a central point. While there are superclusters of galaxies within the universe, superclusters themselves are relatively evenly distributed as far as we can see. This same pattern is observed in the Cosmic Microwave Background, with matter relatively clumpy in locations where galaxies formed but relatively equally distributed.

Gaps in the Big Bang Theory

Gaps in the Big Bang Theory

If the universe arose due to a Big Bang, there was a point and time where all matter in the universe was contained in a single tiny point. What happened to trigger this massive release of matter and energy? And was the universe like before the Big Bang?


Another question is what lies beyond our universe. If the universe began at a single point and time, there is a finite edge to the universe marked by the outer boundary of matter. This is the outer boundary of the explosion. What lies in the dark regions beyond that edge?

Another gap in the Big Bang theory is what happens when the energy that forced the universe to explode into existence runs out. Will the universe’s expansion slow? If so, then based on Einstein’s theory, the universe would collapse in upon itself. This would explain the source of the Big Bang and what happened before. The universe collapses to a single point before the forces within it force it to expand. What existed before the Big Bang was a prior cycle of expansion and contraction. However, if there are not enough gravitational and other forces to keep the universe from expanding forever, we have another problem. Shall the universe expand away until there are only faint dying white dwarves billions of years hence?

ark energy

The existence of our universe from a Big Bang also leaves open the possibility of other Big Bangs occurring billions of years in the past or the future, billions of light-years away.

There are four known forces in the universe: gravity, strong nuclear force, weak nuclear force, and electromagnetism. None of these forces are strong enough to trigger the Big Bang. We do not know what force is strong enough to force all matter into the universe to scatter across a huge volume of space and keep expanding several billion years later. Dark energy is the name used to explain the mysterious force that is propelling the universe forward. It is estimated to account for three-quarters of the universe’s mass. However, we don’t have solid physical proof of dark energy, unless it resides in massive amounts of dark hydrogen that we haven’t yet proven to exist.

Also Read: What if the Sun Disappeared?


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