Imagine the Universe!
Imagine Home  |   Ask an Astrophysicist  |  
Ask an Astrophysicist

The Question

(Submitted March 28, 1997)

I understand that the cosmic particle horizon is located about 20 billion light years away, in all directions, from me. Light coming from objects located past the horizon cannot be seen because the light has not had enough time to reach me yet. But doesn't the cosmic particle horizon expand with the expansion of the Universe. Therefore, light that I couldn't see before can be seen in the future. Is this conclusion sound?

The Answer

The cosmic particle horizon is related to the age of the Universe. Its size certainly grows, but with the age of the Universe, not with the expansion of the Universe. As the expansion slows, we certainly would see more in the future than in the past. But, of course, the time scales for this to happen are very large.

Jim Lochner
for Imagine the Universe!

Previous question
Prev
Main topic
Main
Next question
Next

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

DVD Table of Contents
Educator's Index