The Big Bang Theory

The Big Bang Theory goes along with cosmology in an attempt to explain how the universe developed from a very tiny, dense state into what it is today. It proposes that approximately fourteen billion years ago, the universe that we know today was only a few millimeters across. The "Big Bang" marks the exact moment of the birth of the Universe. At this moment space and time came into existence and all the matter in the cosmos started to expand. Through the remarkable analysis of scientists, such as Albert Einstein, Alexander Friedmann, and Edwin Hubble we have been able to unravel previously incomprehensible pieces of information. Such information includes the Theory of General Relativity and the epic realization that the universe has been since expanding from a hot, miniscule state into the vast and much cooler cosmos that we currently inhibit. (1) (2)

Cosmological Time Line
The events after the Big Bang have been calculated and summerized by the milliseconds, explaining the inflation of the cosmos, eventually leading to the combination of protons and neutrons and ultimately the formation of our Universe.

Illustrating the concept of singularity

Before the "Big Bang"
When hypothesizing the beginning of our Universe, people question what happened before the "Big Bang".
This state is defined as a region of singularity. At this time gravitational forces are so strong that not even
the best theories for describing finite structure of our universe could up-stand. Specifically, the term
singularity represent a point where the curvature of space-time is infinite, embodying zero
volume and infinite density. During this time, it is shown that all four of the fundamental forces were unified. Here, only energy existed. This very hot, condensed singularity of space and time then rapidly expanded. This expansion was the start of the "Big Bang" (4) (7)

The "Big Bang"

10 -43 second: The instance that time began after the Big Bang, is measured as the time up to the 10 -43 second, with temperatures climbing to 1032 degrees Kelvin. This moment is known by scientists as the Planck epoch. It is so significant in that up until this time, the shortest possible period of time, the force of gravity is said to be just as strong as the fundamental forces. If antimatter and matter have the same force, both being controlled by the background energy of the universe, this implies that the universe was composited as one, unified force. (5) (6) (7)
10–43 seconds to 10–36 seconds: Is known as the Grand Unification. The GUT is when the force of gravity begins to disconnect itself from the rest of the fundamental forces, or super-force. At this instant the preliminary elementary particles started to form. The Universe at this state is a hot, dense cluster of particles, such as quarks, antiquarks, and photons all balanced with each other.(5) (7)

10–36 seconds to 10–32 seconds: Is referred to as the Inflationary Epoch. At this time scientists, such as, Alan Guth pinpointed that the universe under-went an extremely rapid expansion, as a result of the empty space vacuum. Through this inflation of the universe, the universe it said to have grown from the size of an atom to the size of a grapefruit begins at 10 -43 second. This growing was a result of separation of one of the main forces, the nuclear force.(5) (7)

10–32 seconds to 10–6 seconds: This moment is referred to as the Electroweak and Quark epoch. In this time span, the strong nuclear force separates from the rest of the remaining fundamental forces, while particle interactions create large numbers of exotic particles. The particles eventually take on mass, allowing to create a universe made entirely out of mass supporting radiation. In addition, Quarks, electrons and neutrinos combine together in massive amounts all while the universe substantially gets cooler. As a result, the fundamental forces are able to return to their initial forms. The surplus amounts of quarks, allow for matter to eventually form. (5) (7)

10–6 seconds to 1 second: The Hadron epoch refers to the time when the temperature of the universe cooled to immensely, allowing quarks to combine and form proton and neutron like elements known as Hadrons. Ultimately, this period consisted of a random combining and re-combining of protons and neutrons. Governed by the rule that the overall change and energy must be conserved. (5) (7)
1 second to 3 minutes: The Lepton epoch refers to the period when the universe was still too hot to form into atoms, charged electrons and protons prevent light from shining in. So the universe is at a stage of extremely hot fog. In this stage as a result of the hadrons and antihadrons annihilate each other the leptons (electrons) and antileptons dominate the mass of the universe. (5) (7)
3 minutes: Known as the The Nucleosynthesis Epoch. This stage is when the remaining free neutrons and protons fused together to form compounds such as 2H and 4He. Ultimately seventy-five percent of the universe is Hydrogen while twenty-five percent is Helium. (5) (7)

300,000 years: The Recombination Epoch represents the time when electrons & nuclei combine into neutral atoms. This period represents the earliest epoch that we are able to directly observe the universe using photons. Because of which our universe is transparent,and photons begin streaming out into space. During the stage the Cosmic Background Radiation is originated. (5)
The "Dark Ages" and Emergence of Galaxies: This represents the time after the Recombination epoch, but before the first generation of stars formed, therefore this Epoch is known as "The Dark Ages". During this period there is no visible or infrared light as a result of there being no stars. In regards to the elements in the universe, hydrogen and helium are neutral. Activity in the universe has tailed off dramatically as a result of the remininents of diffused matter. This means there were very low engery levels and very large time scales. Ultimately, the universe is dominated by mysterious dark matter. (5) (7) (14)
Time of rapid evolution: Represents the period when matter density drops substantially. This matter beings arranging itself into large-scale structures through the gravitational collapse. Then five hundred million years ago: First generation of stars form, ending the "Dark Ages". Quasars first form. First heavy metals made by the first supernovae. The first generation of stars form as smaller clumps of gas combine. This ends the "Dark Ages". After the "Dark Ages" the first heavy metals are created by the first supernovae creating the planets we know today. Eventually, starting from fifteen billion years ago and leading up to present day, galaxies cluster together do to the force of gravity and old stars start to die of, emitting elements into space, to create new stars in a constant recycling of starry products. (14)

Common Misconceptions


People often believe that the Big Bang refers to a single explosion in space. This is not true however, there was no explosion. Instead, our universe was and still is continuously expanding. Scientist have compared this phenomena to a balloon. Picture a balloon gradually expanding into the size of our universe, today. This is what the Universe is doing. (13)

Also, people often think of the singularity existing as a tiny ball of fire within space. However, scientist also disprove this misconception by explaining that space didn't exist before the Big Bang, therefore there was no way for this singularity to exist within space. Rather, scientist show that the singularity "didn't appear in space; rather, space began inside of the singularity". (13)

Albert Einstein

The Big Bang Model's foundation is built from two genius revelations found by Albert Einstein.
First in 1916 he developed the General Theory of Relativity, which he proposed as a new theory of gravity. This theory is a response to Isaac Newton's original theory of gravity, in proposing that gravity reigns true for beings in motion, not just those in rest. Originally Newton's understanding of gravity expressed that it was only possible for bodies at rest or moving very slowly compared to the speed of light to experience the force of gravity. (9)


Alexander Friendmann
In 1922 this Russian physicist responded to Einstein's field equations by providing a set of solutions.This solution came to be known as the Friedmann-Lemaitre-Robertson-Walker cosmological model his solutions to Einstein's field equations provided early evidence that the universe was in fact expanding. These solutions have served as the for much of the current theoretical work on the Big Bang and other models concerning the universe.(8) (9)

The Equation used to find the solution to Einstein's field equations

Edwin Hubble
In 1929 American astronomer, Edwin Hubble, provided some of the greatest supporting evidence for the Big Bang Theory with his discovery that the light from distant galaxies was universally shifted toward the red end of the spectrum. Ultimately these findings supported that the galaxies were moving away from each other. He found that the farther away the galaxies were, the faster away they moved. Thus showing that the universe is expanding uniformly. (9)


George Gamow

In the 1940's he designed a theory that fit with Friedmann's solutions in which the universe expanded from a hot, dense state, working off recent discoveries in quantum theory. Gamow speculated, that the would have particles that could not combine after five minutes of existence, however as the expansion began the temperatures would decrease and nuclear fusion would occur. He explained that atoms would configure as protons and neutrons would link to each other. Gamow also believed that all the elements in the Universe were created at this one time. One year later however, it was proven that Gamow's math didn't up-stand scientific scrutiny. (3) (9)


Fred HoyleThe man infamously responsible for the term the "Big Bang". He coined the phrase on a public broadcast in response to the recent findings of George Gamow. He referred to the new theory as a ridiculous "big bang." believed that Gamow's theory was irrational because it required something to exist before the Big Bang, however we are not able to know what that is. Instead, Hoyle proposed that there is no need for an initial explosion, rather he states that our universe is continuously expanding. This idea was backed by physicists. (12)

Take a Trip through our Universes Timeline!Big Bang Flash Timeline!

Works Cited

1.WMAP Science Team, "Cosmology: The Study of the Universe,"
NASA's Wilkinson Microwave Anisotropy Probe,last modified June 6, 2011,