is the universe is expanding, then that means that it was smaller,13 billions years ago,how big was it?

Answer 1

Do you really mean 13 billion years ago? Or do you mean how small was it when it started?

The universe is 13.7 billion years old. It started out only about 1.6×10^-35 meters across -- much *much* smaller than the nucleus of an atom. We say that the universe was 10^-43 seconds old then, but we really don't know what things were like "before" then. We're not really sure that there was a "before" -- some scientists say that time itself started then.

By the time it was 380 million years old, it was a lot bigger: about 300 million light-years.

Answer 2

It depends how far you go back in time. We can, at this time, not tell what the smallest size of the universe was, because that would require detailed knowledge about the quantum theory of gravity and we do not have that.

The question of size is also a bit complicated because the size of the universe is not the same as the size of the visible universe. The size of the visible universe can, theoretically, be measured, the total size can only be estimated from model parameters, so it depends on how much you trust your physical model and how far back the extrapolations from current measurements take you before the bounds on error bars explode.

Answer 3

According to theory the singularity of the big bang was an intensely hot point with no radius, this point existed for 10-43 sec before it began to expand.

Answer 4

Theoretically, it was smaller than the period at the end of this sentence, just before the Big Bang.

Answer 5

it is not that great deal bigger looking at how big the universe is, and the fact that most the of it expanded with in a few minutes after the big bang.

Answer 6

Well, given that you must reverse all movement outward to start the calculations,

If you follow all expansions in reverse, you should come down to a point at some stage in the process of mathmatical reversal of the expansion process. Now, for most of us, the idea of everything that exists originating from a single point gets a bit hairy.

So, let's bypass that issue and direct all viewers, instead, to a highly interesting news release on "Magnetars". Read and understand this article before throwing rocks at the single point concept.

Please go to:

http://www.astromart.com

Read the main feature article about discovery of "Magnetars."
When you read this article, pay specific attention to the total mass mentioned, and then to the "size" of the object which contains that total mass.

Regards,

Zah

Answer 7

if you split an atom, something we cannot even see, it explodes 1,000,000,000 times it size, thats a big bang, time is relitive, how many years where the galaxies living and thriving inside? millions if life is inside and can pass billions of years to a small planet inside all makes a split second to us, but a billion years inside, get it?