Horizon Problem

[asterroc]

I've been talking lately with jethereal about a cosmology conundrum. The universe is roughly 13.7 billion years old. Due to the speed of light, this means that we cannot see objects further away than 13.7 billion light years. The universe is actually larger than that 13.7 Glyr due to inflation, but we just can't see those parts because there hasn't been enough time for the light to get to us yet. Let's assume there's a quasar located, oh, 15 Glyr away from us. It's moving away from us true, but at a slower speed than that of light. We'll assume that it's actually 15 Glyr away when the Universe hits 15 Gyr old, and our horizon hits the quasar.

The question is as follows: What do we see when the horizon gets to the quasar? Jethereal proposed that it springs into our view fully formed. I countered that the quasar had to form at some point in time, so where did the light from its formation go? I proposed that the light from formation gets to us when the horizon hits the quasar.

Neither of us are actually cosmologists, so we're not sure of the answer. Anyone else want to weigh in?

x-posted

Comments

[zandperl.livejournal.com]

I'm starting to doubt myself though. As mentioned above to xoder, if we're saying that we'll be able to see the birth of a quasar, then before that we should be able to see the host galaxy (assuming infinitely good telescopes). There's nothing to my original scenario that distinguishes when the horizon gets to the quasar's location. Therefore, I don't think my original scenario can be right.