Question

In astrophysics as according to Big bang theory generally people say space is expanding. WHY?

Answer 1

The reknowned astronomer, Edwin Hubble, discovered that the spectra of galaxies and galaxy clusters was red shifted. This happens when light is coming from a source which is relatively moving furthur away.
It has been observed that all galaxies and galaxy clusters are moving away from earth and from each other. This effect gets pronounced the furthur away we look. so bodies in the universe furthur away are moving ever faster away from each other.
Hence, we deduce that the universe must be expanding. it does not mean that it is like a big explosion. It means that if you imagine this whole universe as a container. The container itself is getting bigger and bigger.
the famous example mostly quoted to explain this is the Hubble balloon. look for it.

Answer 2

As you said, If we consider space expanding similar to expanding balloon and to expand a balloon we need some source like pump or something like that. As according to this what is that source expanding this space. Because for every effect there should be some cause

Answer 3

Hay @zaphodplaysitsafe please reply me.

Answer 4

Hi @M_Vamshi_Kumar_Reddy, one thing to take care in envisioning this with the balloon analogy is - The 2 dimensional surface of the balloon represents the universe(in 3 dimensions of space, and time). so the whole universe is signified by the balloon surface itself in this analogy. There is NOTHING inside the balloon. every bit of the universe, its every dimension is on the surface of the balloon. Now think about it.

so every bit of the space is expanding. its not expanding inwards to outwards.. its expanding everywhere.

And when you ask its reason.....the universe smiles back at you with the mysterious Monalisa smile. We don't know that.

Answer 5

I feel questioning universe is just like questioning my creation. Its great to be felt that.