How did people come up with the theroy that the singularity was nothing or just a tiny spec? Is there any evidence that supports this theroy? |

This is a common question, and though it has been discussed previously, I'll give a brief self-contained answer here.

The singularity is not really a "thing", but a condition in which physics breaks down.

The word "singularity" is a mathematical term. It refers to a condition in which a function diverges or becomes undefined. For example, the function f(x) = 1/x has a singularity when x equals 0.

The theory we use for gravity and spacetime is general relativity. When applied to the universe to track the "scale" and "curvature" of spacetime into the past, the functions diverge to infinitesimal scale and infinite or undefined curvature. This is the singularity; and it marks a point at which classical physics breaks down.

As yet, we do not have a physical theory able to describe these conditions. It will require a combination of relativity and quantum mechanics; which is an unsolved problem in physics.

The theories for relativity, spacetime, and the expanding universe are obtained in the same way as all scientific models. Hypothesize and test.

There is copious evidence for relativity, and for the expanding universe. There is no credible basis for doubt that the universe has expanded from conditions of extreme heat and density some 13 or 14 billion years ago.

It is a mathematical theorem that relativistic physics diverges to a singularity of unbounded density and infinitesimal scale as you extrapolate into the past. This marks a point at which we don't know what is going on, because existing physics can't handle those conditions.

I'm choosing words carefully here. "Scale" is a bit like "size". It does not mean that there is any particular object, like a "speck", which developed into the universe. It means that the *entire universe* was compressed. Everything we see now was once contained within a small region; but this does not mean that this region had any edge.

Imagine we could look into the distant past, when the whole universe was hot plasma a bit like the middle of the Sun, extending in all directions without edge or bound. Now draw an imaginary sphere within that thick hot dense material. That sphere is the "region" which contained all the matter visible today. "Scale" is just an indication of the factors by which things have expanded.

Cheers -- Sylas