# Particle horizon in Lemaître model

1. Dec 18, 2011

### EhsanZ

What is the exact calculation of Particle horizon in Lemaître model? Does it exist? Is it finite or infinite?
Can anyone calculate that integral?
Thanks

2. Dec 18, 2011

### Markus Hanke

The particle horizon marks the boundary between observable and un-observable parts of the universe, and yes, this integral can be calculated using the time-dependent scale factor function taken from the FLRW metric, as well as observational parameters. So far as I could find ( these things change pretty regularly ) the furthest know object to date has a redshift factor of z=8.2 which would be equivalent to a proper distance ( remember, this is not the same as light-travel distance due to the dynamic expansion of spacetime ) of about 30 billion light years. Reference :

http://en.wikipedia.org/wiki/Observable_universe

If you do the maths from the integral you arrive at a figure of about 46 billion light years.

Last edited: Dec 18, 2011