Does the scale factor need to be normalized?

[Ibix]

@ibis Is the particle horizon calculation correct only for zero initial size of the universe, or any initial size?

What do you mean by "initial size of the universe"? The scale factor is always zero at the start of an expanding universe.

 

[Jaime Rudas]

@ibis Is the particle horizon calculation correct only for zero initial size of the universe, or any initial size?

It is correct even for an infinite initial size.

 

[hedgehug]

What do you mean by "initial size of the universe"? The scale factor is always zero at the start of an expanding universe.

If spacetime already existed at the BB, then the universe already had non-zero, initial size.

 

[hedgehug]

It is correct even for an infinite initial size.

That solves my problem. Thank you.