The Big Bang is a massive event that occurred 13 billion years ago, leading to the formation of the universe. Read more for additional facts...

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The Big Bang

Hello Readers!

This post is going to be about The Big Bang.

The Big Bang Theory is a theory that revolves around a catastrophic explosion that happened 13 billion years ago which led to the birth of the universe and its evolution to date.

The evolution of the universe is divided into many stages. Let's cover them.

Stage 1: Firstly, the universe was made up of nothing. Not even space or time existed. Suddenly the universe appeared from nothing. It grew and finally exploded, emitting light, heat, and other types of radiation. 

Stage 2: The universe appeared as energy. At this point, the universe's temperature was 10 to the power of 28 K. The energy formed subatomic particles and antiparticles. Most of these annihilated one another and turned back to energy, but some were left out. At this process, the universe was less than a millionth of a second old when hydrogen and helium atoms began to form. 

 

^{Stage 3: The universe expanded over a trillion kilometres in a second. At 390,000 years after the big bang, the universe was a vast cloud of hydrogen and helium atoms. Before this, the universe was dense like a soup and light had to collide with atoms to move forward. But now, the temperature dropped to 3000 K, The cosmic background radiation was emitted. As there was nothing to hinder the direction of light, it moved in a straight line. This was called The clearing up of the universe.}

Stage 4: At 400 million years, the clumps of dust and gas formed rotating discs and due to nuclear fusion, the centres began to explode and shine as the first stars. The stars were held with gravity within big clumps called galaxies. The first galaxies had no shape but soon they merged and developed spiral shapes. The age of our own galaxy, The Milky Way is 13.56 billion years which suggests it was formed when the universe was 560 million years. At 8 billion years, the expansion of the universe began to accelerate.

Stage 5: At 9 billion years, the solar system formed through a nebula containing gas and dust.

the sun first forms and then the planets.

So, many events took place in the universe in 4.8 billion years and the universe came to its present state after 13.8 billion years. 

Not all scientists believe in this theory but few discoveries were made that changed their opinion.

1. Light from distant galaxies appeared redder in the colour spectrum than it should be.

The Color Spectrum

In 1929, astronomer Edwin Hubble observed light coming from distant galaxies was redder than it used to be. This is called Redshift, which means that the light was shifting to the red end of the spectrum. It means that the galaxies were moving away from us.

2. Cosmic Microwave Background Radiation

The radiation, as discussed earlier is the remains of the Big Bang. As mentioned earlier, this radiation was 3000 K hot. Because of the Doppler effect, it got stretched and is currently observed as 3 K waves (The temperature of the universe is also 3 K). 

Cosmic Background Radiation has travelled around the whole universe and is coming to earth after 13.8 billion years. Meanwhile, the universe has expanded about 1000 times. This 3000 K light got stretched into 3 K waves.

Doppler effect: To understand this, let's take an example. If you are walking on the streets,  you stop and find a car whose engine is on. The sound that travels to you from the car is in the form of waves. But once you start walking, the incoming waves get stretched into longer waves from shorter waves, and by the time, they reach your ears, your brain will think that the car is rushing onto you. But when you stop, the waves get shorter and you will hear the idling car engine sound.

Therefore, it is a phenomenon where frequency of sound changes with respect to the speed and position of the observer.

Thank you for reading!

Aditya VN Kadiyala