Question

Why is the universe expanding?

Answer 1

Hint:Here, you are asked the reason why the universe is expanding. Here, you need to consider various theories like, Einstein’s General theory of relativity, Hubble’s discovery and the concept of dark energy. You can consider gravity as well in order to bring your thoughts to a conclusion which may lead to the answer that you are looking for.

Complete answer:
According to Einstein’s belief, the universe was an infinitely large blimp, all encompassed. Einstein’s general theory of relativity suggested that the universe is spatially curved, homogenous and is governed by a single force known as gravity. Now, if the cosmos is governed by a single force, that is gravity, every matter in the universe would be impelled to this law and would be supposed to get mutually attracted to each other.

As a result, the universe would actually disintegrate under its own weight. This model of the universe is definitely not the case. So, Einstein introduced a new cosmological constant in his equations according to which the inexorable pull of gravity is neutralized, meaning neither contraction nor expansion.

But Hubble came to the discovery of the phenomenon known as the red shift. The wavelengths of the light emitted by the galaxies were observed to be stretched indicating that the galaxies are moving away from us, which means that the universe is expanding.

The expansion indicates that there are two forces that are in act, one is the force of gravity that is the attractive force and the other one is the unknown repulsive force that is moving the galaxies away from us. The force of gravity works on an object but the unknown repulsive force works on space instead. This repulsive force is known to be dark energy. So, dark energy is the reason why the universe is expanding.

Note: Here, we have discussed in brief about Einstein’s theory of general relativity, Hubble’s discovery of the phenomenon known as the red shift and a little about dark energy. You need to think of the reason for the expansion of the universe in the same pattern. If only gravity would have acted, it would be catastrophic. You need to keep in mind the above mentioned points.