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The Big Bang Theory states the universe began as a hot, infinitely dense point similar to a supercharged black hole. About 13.7 billion years ago this singularity violently exploded. From this explosion (bang) came all matter, energy, space and time. After this explosion, there came 2 stages of evolution that shaped the universe:
A.) The Radiation Era- Within 30,000 years after the explosion. (Radiation dominates the universe). This stage is further divided into 8 epochs (A moment in time from which nature or situations change to the extent of marking a new era). In summary this is what happened throughout the 8 epochs: Electrons and quarks (quarks are fundamental constituents of matter that interact to form protons and neutrons) are formed. As the universe begins to cool, the quarks bind together to form protons and neutrons, the building blocks of atoms. The protons and neutrons fuse into nuclei which forms the 1st chemical element, Helium.
B. )Matter Era- 30,000 years after the explosion. (Matter dominates the universe). This stage is further divided into 3 epochs. In summary this is what happened throughout the 3 epochs: Electrons fuse with nuclei and thus Hydrogen, the 2nd universal element after Helium, is formed. Hydrogen combines with Helium to form atomic clouds. Quasars begin to form. Quasars are extremely bright active galactic nucleus, in which a supermassive black hole is surrounded by a gaseous accretion disk. These became the seeds of galaxies. Stars begin to form in these galaxies. The first stars and galaxies appeared within about 200 million years of the Big bang. The formation of stars continued had a ripple effect and shaped the universe. As big stars lived and died, they blew up and created new elements. With more and more new elements forming, new materials are formed such as dust, ice, rocks and minerals. Through heat from the stars, helium and hydrogen are able to create the remaining elements. Through the continued forming of new materials and expansion of the universe, our Sun and solar system appeared about 4.5 billion years ago. By 3.7 billion years ago, life had began to emerge on Earth.
EVIDENCE OF BIG BANG:
1.) Redshift of galaxies.
The light we observe from galaxies has been stretched by the time it reaches us. It looks redder than it should. This redshift is the result of galaxies moving away from us. Observations show that pretty much everything in the Universe is moving apart. The redshift of distant galaxies tells us the Universe is expanding. If you could wind time backwards, you would see galaxies getting closer together. If you could go back far enough, everything in the Universe would have been in one place.
2.) Cosmic Microwave background.
A long time ago, the whole Universe was very hot. As it grew in the size, the heat left a “glow” which fills the entire Universe. The Big Bang theory predicts this glow should still exist. It also predicts that we should be able to detect this glow as microwave light. Scientist have found this Cosmic Microwave Background. They have accurately measured it using orbiting detectors. It is very good evidence that the Big Bang theory is correct.
3.) Mixture of elements.
Some chemical elements were created soon after the Big Bang. Elements like hydrogen and helium. The Big Bang theory predicts how much of each element was made in the early universe. When astronomers look at very old galaxies and stars, the amount of each chemical they see agrees with the Big Bang theory.
You cannot look for this evidence in new stars, like the sun. This is because newer stars contain chemical elements made by older stars. So the chemical make-up of new stars is very different from stars which existed soon after the Big Bang.
CRITICISMS OF BIG BANG.
1.) The universe began out of nothing.
The theory violates the first law of thermodynamics which states you cannot create or destroy matter or energy. Proponents of the big bang theory say that such criticism is unwarranted for two reasons. The first is that the big bang doesn’t address the creation of the universe, but rather the evolution of it. The other reason is that since the laws of science break down as you approach the creation of the universe, there’s no reason to believe the first law of thermodynamics would apply .
2.) Misinterpreted evidence.
Some astrophysicists and cosmologists argue that scientists have misinterpreted evidence like the redshift of celestial bodies and the cosmic microwave background radiation. Some cite the absence of exotic cosmic bodies that should have been the product of the big bang according to the theory.
PS: There are more criticisms but they were just too technical to understand and as such I didn’t think they are worth posting here and lengthening an already long post.
Sources:
https://storymaps.arcgis.com/stories/2e16464e7d3549069e13a18c2689ce99
https://www.schoolsobservatory.org/learn/astro/cosmos/bigbang/bb_evid
https://science.howstuffworks.com/dictionary/astronomy-terms/big-bang-theory7.htm#:~:text=Here’s%20a%20rundown%20on%20some,universe%20began%20out%20of%20nothing .
hii ndio inaitwa non sequitur. You could google enough and find out but you’re either too lazy or too dumb to understand.