Now how

How did the big bang create the universe?


Nowadays, when people mention the big bang theory, they think of Sheldon Cooper and his utter lack of self-awareness during embarrassing social interactions.

The title of the show featuring the antics of a pretty blonde girl and four brilliant nerds, though, was actually derived from one of the most important astronomical theories.

The big bang theory describes the creation of everything in the universe. According to this theory, all the matter in the universe came into existence at the same time during an event known as the big bang, which happened about 13.7 billion years ago.

At that time, all matter was compacted into a single point with infinite density and intense heat called a singularity. Many people are under the misconception that the big bang was an explosion in which this singularity unpacked and propelled matter out across space, thereby instigating the birth of the universe. This is understandable – the name “the big bang” sounds like it ought to involve something exploding, doesn’t it? The big bang, though, is actually the expansion of the universe originating from that one singularity.

When the big bang happened, after the initial moments of high, intense energy radiating from the density and heat of the singularity, the universe expanded rapidly so that everything became less dense and cooled down. In just a few seconds, the expansion caused the singularity to stretch out all across space (Coffey).



The reason why the big bang theory is so popular and so widely accepted is because so far, all the observations we’ve made of the cosmos support this theory. The theory originated in 1929 when Edwin Hubble discovered that everything in the universe is moving away from everything else. Hubble explained this by theorizing that the universe was expanding in every direction.

If this observation was reversed, then this would indicate that the universe was smaller in the past than it is now. Continuing in this vein, there must have been a time when the universe was only half the size it is now, a quarter of the size it is now, and so on. If we go back in time far enough, we could theoretically trace the shrinking of the universe to a time at which there was only an infinitesimally small point, the aforementioned singularity (“Big Bang”).

Since there have been no discoveries to dispute this theory and this seems to be the most sensible theory for how everything in the universe was created, then it is an incredibly important one to understand in the field of astronomy.


Because of the limitations of the laws of science, there’s no way to determine the exact moment when the universe came into existence. However, scientists are able to look at what happened during the first moments after the big bang occurred.

The singularity was so small that it has to be observed using quantum physics, which deals with things on the smallest scale scientists have ever postulated. At the beginning of existence, the universe had a temperature of 1 x 1032 degree Celsius and only covered a region of 1 x 10-33 centimeters. It’s hard to believe that expanded to become the universe spanning billions of light years we know today!

bang3As tiny fractions of a second passed after the big bang, the universe expanded rapidly. It doubled in size several times in less than a second and cooled during the process.

At t = 1 x 10-11 seconds after the big bang began, the universe had expanded to a point where we could graduate from speculating on events from the quantum viewpoint to being able to simulate the environment in lab conditions with particle accelerators.

Then, the period of standard cosmology began .01 seconds after the big bang. Here, protons and neutrons are fully formed. After a full second,the nuclei of light elements like hydrogen, helium, and lithium were forming. However, the stable atoms could not be formed yet because the conditions were still too dense and hot for electrons to join the nuclei.

After 100 seconds, the universe’s temperature cooled to 1 billion degrees Celsius (but it was still too hot for electrons to bond with nuclei). After 56,000 years, the universe had cooled to 8,726 degrees Celsius and the density of the matter distribution in the universe matched the density of radiation. After 324,000 years, the universe had expanded enough to cool down to a temperature where protons and electrons could finally combine to form neutral hydrogen atoms.

At 380,000 years after the initial event, the universe became transparent so that light could shine throughout the universe. For the 100 million years or so following, the universe continued to expand and cool. During this time, small gravitational fluctuations caused particles of matter to cluster together, collapsing gases in the universe into tight pockets. 100 to 200 million years after the big bang started, stars formed from these pockets.

Stars clustered together to form galaxies. Some stars went supernova and exploded, shooting out matter across the universe. This matter includes the heavier elements we find in nature (everything up to uranium). These galaxies also in turn formed their own clusters, which we know now as solar systems. Our solar system formed about 4.6 billion years ago.

Today, the temperature of the universe is -270 degrees Celsius and our best guess of the size of the universe is 1 x 1029 centimeters across (6.21 x 1023 miles) (Strickland).


Well, we’ve come a long way from being packed inside one infinitesimally small point.


 Written by Constance Kaita

Works Referenced 

Images courtesy of,,, and

“Big Bang.” 11 January 2006. Web. 30 July 2013.

Coffey, Jerry. “What Is The Big Bang Theory.” 7 February 2010. Web. 30 July 2013.

Strickland, Jonathan. “How the Big Bang Theory Works.” 18 June 2008. Web. 30 July 2013.

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