Question

Why is the universe expanding?

Answer 1

1. Initially scientists believed that the universe expanded because of momentum. Right after the BIG BANG THEORY, our universe received something called dark energy and since then the universe has only expanded in an accelerating manner.
2. Then the question raised "WHY IS THE UNIVERSE EXPANDING?".

There are a few interesting concepts that answer this question.

1. THE DARK MATTER-The dark matter or dark energy which had been radiated after the big bang theory is supposed to be the main reason causing the expansion of the universe. Also on a daily basis, there are a lot of radiations emitted which we are not aware of. They too contribute to the dark matter.
2. MODIFIED GRAVITY-Through the Einstein's equations it is clear that gravity has been calculated accurately. But many scientists believe that the equations are not correct and are a mixture of many complicated calculations that we do not know about.
3. INCONSTANT DARK ENERGY-As we know the dark energy is present in the whole universe that is all the galaxies. Scientists say, what if the energy is inconsistent and due to the pressure of the dark energy the universe is expanding. There could be endless reasons to why this is happening but these are the most believed ones.

Due to the above reasons, the universe is expanding.