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Big Bang: 10 Facts to Make You Thinking About Universe

If you have a science background or if you paid enough attention in your Physics classes at school you probably know that Big Bang Theory is a theory describing the evolution of our universe.

It is based on the model that the Universe was very hot and dense at the beginning and expanded rapidly to the Universe that is now known. Here are 10 incredible facts about the Big Bang that you may enjoy and share with your friends.


1. The Big Bang is not the explosion of matter moving outward to fill the entire universe.

Cute ethnic child inflating white balloon in studio.
Monstera from Pexels. Source.

Big Bang is a model describing how the Universe formed and works, not a description of an actual explosion. It actually describes a rapid expansion of space, rather than an explosion in the pre-existing space. In the Big Bang theory, space itself expands with time everywhere and increases the physical distances between comoving points.

A good example to visualize Big Bang and the expansion would be an inflating balloon, as you blow the balloon, the points on the balloon which were closer will get farther and farther.


2. The astronomer who is credited with coining the term Big Bang, favored a Steady-State model of the Universe.

The detailed, all-sky picture of the infant universe created from seven years of WMAP data. The image reveals 13.7 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies. The signal from the our Galaxy was subtracted using the multi-frequency data. This image shows a temperature range of ± 200 microKelvin.

The English astronomer Fred Hoyle is the first person to have used the term “Big Bang” to describe the theory of the expanding Universe. He first used the term “Big Bang” during a talk for a  BBC Radio broadcast in 1949.

He said, “These theories were based on the hypothesis that all the matter in the universe was created in one big bang at a particular time in the remote past.” It was widely reported that he used the term as a pejorative, but he denied this and said he used the term to highlight the striking differences between the two theories.


3. The first direct observational evidence for the Big Bang Model was Hubble’s Law.

This illustration shows the three steps astronomers used to measure the expansion rate of the Universe to an unprecedented accuracy, reducing the total uncertainty to 2.3 %. Astronomers made the measurements by streamlining and strengthening the construction of the cosmic distance ladder, which is used to measure accurate distances to galaxies near to and far from Earth.
Credits – NASA, ESA, A. Feild (STScI), and A. Riess (STScI/JHU)/CC BY 4.0/Source

Hubble’s law states that galaxies are moving away from the Earth at speeds proportional to their distance. The farther they are the faster they are moving away from Earth. The velocity of the galaxies has been determined by their redshift, a shift in the frequency of the light they emit toward the red end of the spectrum.

Hubble’s law is considered the first observational evidence for the expansion of the Universe. Today, it is one of the pieces of evidence most often cited in support of the Big Bang model of the Universe.


4. There is no currently available physical theory to describe the earliest stage of the Big Bang.

Hundreds of thousands of vibrant blue and red stars blaze in this image taken by NASA's Hubble Space Telescope. Hot bluish-white clusters of massive stars are scattered throughout the galaxy, interspersed with numerous dustier, reddish regions of current star formation. Massive dark clouds of gas and dust are silhouetted against the starlight.

Planck epoch or Planck era is the earliest stage of the Big Bang before the time passed since Big Bang was equal to the Planck time,  approximately 10−43 seconds. There is no currently available physical theory to describe such short times, and it is not clear in what sense the concept of time is meaningful for values smaller than the Planck time.

It is assumed that the quantum effects of gravity dominate physical interactions at this extremely small time scale. At this scale, all the four fundamental forces of the Universe are assumed to be united.


5. After Big Bang, at the end of the Inflation phase, the volume of the Universe was increased by a factor of at least 10⁷⁸!!

The inflationary theory as an augmentation to the Big Bang theory was first proposed by Alan Guth of MIT. Inflation solves the 'horizon problem' by making the early universe much more compact than was assumed in the standard model. Given such smaller size, causal contact (i.e., thermal communication) would have been possible among all regions of the early universe. The image was an adaptation from various generic charts depicting the growth of the size of the observable universe, for both the standard model and inflationary model respectively, of the Big Bang theory.

The Planck epoch was succeeded by the grand unification where gravitation separated from the other forces. At approximately 10−37 seconds into the expansion, a phase transition caused a cosmic inflation, during which the universe expanded to a staggering size and temperatures dropped by a factor of 1,00,000.

Microscopic quantum fluctuations that occurred because of the uncertainty principle were amplified into the seeds that would later form the large-scale structure of the universe. Inflation stopped around the 10−33 to  10−32 seconds after the Big Bang. The Universe expanded by a factor of at least 1078.


6. The accidental discovery of Cosmic Microwave Background radiation made the Big Bang Theory the standard cosmological model of the universe.

The star cluster Westerlund 2 in the Milky Way galaxy, with an estimated age of about one or two million years. It contains some of the hottest, brightest, and most massive stars known. The cluster resides inside a stellar breeding ground known as Gum 29, located 20,000 light-years away in the constellation Carina.

On 20 May 1964, Arno Penzias and Robert Wilson accidentally discovered an omnidirectional signal in the microwave band that filled in the entire space. Their measurements showed that their antenna was having an excess temperature of  4.2K  which they could not account for. 

This radiation is approximately consistent with the blackbody spectrum in all directions. As predicted, this spectrum has been redshifted due to the expanding universe and today measures approximately 2.725 K. The discovery of Cosmic Microwave Background Radiation made the Big Bang Theory the leading model for the evolution and structure of the Universe. Arno Penzias and Robert Wilson were awarded the Nobel Prize in Physics in 1978.


7. During the early phases of the Universe after Big Bang, nuclear fusion occurred for the first time to form nuclei of the light elements.

deuterium-tritium fusion diagram, comma as decimal separator

After a few minutes since Big Bang happened, the Universe started to cool off. At this point, neutrons combined with protons to form the deuterium and helium nuclei in a process called Big Bang nucleosynthesis.

Protons and neutrons combined through nuclear fusion to form the nuclei of the simple elements of hydrogen, helium, and lithium. After about 20 minutes, the temperature and density of the Universe have fallen to the point where nuclear fusion could not continue to occur.


8. Universe is not just constantly expanding, it’s accelerating!

Dark matter has so far defied every type of detector designed to find it. Because of its huge gravitational footprint in space, we know dark matter must make up about 85 percent of the total mass of the universe, but we don’t yet know what it’s made of.

In 1998, two independent projects namely the Supernova Cosmology Project and the High-Z Supernova Search Team used the distant type Ia supernovae to determine the expansion of the Universe. The result was completely unexpected.

They found that objects in the universe are moving away from one another at an accelerated rate. Up to that point, astrophysicists thought that recession velocity would always be decreasing, since all the matter in the Universe attracts each other due to gravitation.

The mysterious “dark energy” is said to be responsible for the acceleration of the Universe. The Universe probably began to accelerate after it entered the dark energy-dominated era about 4 billion years ago. Three members of these two groups were later awarded the Nobel Prizes for their discovery.


9. A reaction that took place in the early Universe after the Big Bang is responsible for the predominance of matter over antimatter in the Universe.

 	Eta Carinae captured by the Hubble Space Telescope.

Baryogenesis is the reaction that is hypothesized to have taken place in the early Universe that caused the predominance of matter over antimatter in the observable Universe. As it was expected that the physics which was working in the early Universe is the physics that works today, matter and antimatter were expected to be produced in the same quantities.

At the very beginning of the Universe, matter and antimatter were in equal proportions and thus there were a nearly equal number of quarks and antiquarks. When the Universe cooled to a temperature the universe expanded and cooled to a temperature of  2×1012 kelvin and quarks combined into matter and antimatter. Antimatter then got annihilated with matter up to the small initial asymmetry of approximately one in five billion, causing the matter to be predominant in the Universe.


10. Big Bang started the Universe, but there are many different scenarios in which the Universe would come to an end.

Composite image showing the visible and near infrared light spectrum This is a composite image showing the visible and near infrared light spectrum collected from Hubble's ACS and WFC3 instruments over a nine-year period.

Astronomers using NASA's Hubble Space Telescope have assembled a comprehensive picture of the evolving universe – among the most colorful deep space images ever captured by the 24-year-old telescope.

Before dark energy was discovered, astrophysicists considered two scenarios for the ultimate end of the universe. Either a Big Crunch – in which the Universe would attain a maximum size and then begin to collapse and become denser and hotter again and end how it all began; or a Big Freeze – in which the average temperature of the universe would very gradually approach absolute zero.

Another scenario which is based on protons being unstable would cause baryonic matter to disappear leaving only radiation and black holes which would eventually evaporate by emitting Hawking radiation. The entropy of the universe would increase so much that no energy could be extracted from it, a scenario known as heat death.

Scenarios involving a hypothetical form of dark energy called the phantom energy predict that galaxies and all matter itself will be torn apart by the ever-increasing expansion rate of the Universe, this is known as the Big Rip.


You may want to see Big Bang Theory Makes You Understand the Universe.


How many of these interesting Big Bang facts did you know? Which one of these was your favorite or was surprising to you? Comment below.


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