ORIGIN OF THE UNIVERSE – Aritro Roy 11H

For a long time, it was thought that the universe was created by a powerful deity, however today’s cosmos theory proves otherwise. The origin of the cosmos theory dates from early 1930s, when Belgian astronomer Georges Lemaitre first suggested what is now known as the Big Bang.

Georges Lemaître - Wikipedia

Lemaitre’s Cosmic egg

In 1927, Lemaitre proposed that universe was expanding from a single point called “Primeval atom” or “Cosmic egg”. He partly derived his theory from Einstein’s theory of general relativity however Einstein dismissed the idea of expansion due to lack of evidence. In 1929, American scientist Edwin Hubble discovered that galaxies move away from the centre of the universe which supported Lemaitre’s theory. Lemaitre, it seemed was on the right track.

Steady-state model

During the time Lemaitre and Hubble were working on their theory, the model that was widely accepted was the steady state model. According to this model, the universe had always existed. Matter formed continually between other galaxies as they drifted apart, and continuous creation of matter and energy kept universe in balance. This idea was mainly supported by British astronomer Fred Hoyle.

Residual heat

A year earlier, Ukrainian physicist George Gamow (right) and American Cosmologist Ralph Alpher (left) had published “The origin of chemical elements “to explain conditions immediately after the explosion of the primeval atom and distribution of the particles throughout the universe. This led to the discovery of the Cosmic microwave background radiation (CMBR)- the residual heat from the Big Bang. The discovery of the CMBR ruled out the steady state theory. CMBR proved that there was a time in the universe where it was very hot, and matter clumped together to form galaxies suggesting that the universe had not always been there. This had destroyed the steady state theory and now the Big Bang theory is the preeminent explanation for how our universe began.

Stars and Galaxies evolve

Astronomers now believe that the first stars formed millions of years after the Big Bang. As the universe became transparent dense clumps of neutral hydrogen gas, it continued to grow under the force of gravity as more matter was pulled in from areas of lower density. When the clumps of gas reached a high enough temperature for nuclear fusion to occur, the earliest stars appeared. These stars were 30 to 300 times as big as the sun and millions of times brighter. These stars were short lived and exploded into supernovae creating heavy elements such as uranium and gold. About one billion years after big bang, the next generation of stars which contained heavier elements and were longer lived, grouped together to form galaxies, but these drifted apart as the universe expanded. Over the years there were fewer collisions and universe became relatively stable as it is today.

An Observable timeline

The Big Bang theory has enabled scientists to get a firm grasp on the origins of our universe, providing a timeline that stretches back 13.8 billion years to its first moments. Crucially most of the predictions are testable. Physicists can recreate the conditions that took place after the Big Bang. This leads us to today, where we are trying to understand the properties of the universe then as compared to now.

The Big Bang and the Misconceptions Surrounding it