“We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special.” -Stephen Hawking
There is always this unanswered question in human brains why are we here? which then leads to, who created this vast infinite universe. Philosophy, Religion and Physics are trying to answer these questions in their own way and people who believe in Physics mostly rest their faith in the great Big Bang that happened thirteen billion years ago.
Although many theories were put forward to explain the origins of universe, the Big Bang Theory emerged as widely accepted among many notable physicsts. The Big Bang Theory got it acceptance mainly due to the promising cosmological discoveries made in the 20th century. This further lead to many other questions
The Physicists observed something very peculiar in our Universe, that our Universe is fine-tuned and even a slightest change in any of the physical constants would make the universe radically different. Though the Einstein’s theory of General Relativity and Quantum Physics don’t support each other but both the theories agree with the fine tuned Universe. A slightly larger quantity of dark energy, or a slightly larger value of the cosmological constant will make space to expand rapidly enough that galaxies would not form. Even at quark level the neutron being heavier than proton is responsible for formation of atoms and we know that light speed has a fixed number and anything that has mass can never travel faster than that number.
Biologists who believe in carbon based life strongly believe in fine tuned Universe concept. Carbon is the element of life and these carbon atoms form in the core of stars by fusion reactions. The helium atoms collide and fuse together to make a carbon atom and that fusion reaction will work only if the energy levels match up in the right way or else the helium atoms would bounce off before they could fuse. The slightest change to either the strong or electromagnetic forces will result in change in energy levels. The values are fine tuned leading to abundant amounts of element of life
The concept of fine tuned universe bifurcated sceintific community into two major groups, one believing in a designer for the Universe and the other believing in a multiverse being created at Big Bang where every scenario is possible and we happened to be exisiting in the one with the exisiting tuning.
While the scientists supporting the Big Bang Theory were trying to explain the pecularities in the observable Universe there were asked to explain what was present before the Big Bang and what caused it. Many Physicists believe that space and time came into existence only at Big Bang. According to Einstein’s General Theory of Relativity space and time together form a space time continuum or manifold which is not flat but curved by the matter and energy in it. Stephen Hawking tried explaining before Big Bang by adopting Eucleadian approach to Quantum Gravity, in his theory oridnary real time is replaced by imaginary time which behaves like a fourth direction of space and the history of Universe in this imaginary time is a four dimesional closed surface like the surface of the earth without end. According to him one can regard imaginary and real time as beginning at the south pole which is a smooth point of space time where the normal laws of physics hold and there was nothing south of south pole so there was nothing around before the Big Bang
There were no proofs to any of the theories that explain the origins of the Universe. Maybe time will give the answers like it always does, Newton was not able to explain the action at a distance(gravity) and Einstein picked where Newton left and Einstein never imagined the existence of black holes and someone else found it from his equations. Time has answered many questions, created advanced civilizations. Time is giving us all the information we need, the physical laws, the values of these physical constants. Maybe there is a purpose that we are getting this informtion, maybe time will create a super advanced civilization who will have the full understanding of the universe who colonizes galaxies. Maybe this super advanced civilization is reponsible for the Big Bang and a fine tuned universe. Maybe we humans fine tuned the Universe for our own existence.
One explanation could be that time exists as circular loop and everything that happend will happen and everything that will happen has happened. There comes a time in future when advanced humans who have full understanding of the universe will make the Big Bang possible and it can be either to save the human race or save the universe or it could be a advanced accidental scientific experiment