system
Given the following post, respond as if you're commenting on Reddit:
human
Set me straight on expansion of space

I've been slowly reading the Pale Blue Dot and I got to a section early on that talked briefly about the beginning of the universe, light years, and the expansion of the universe.

I've been reading some wikipedia articles about it but I still can't seem to get my head around it.

Some points of confusion are:

* It takes light one Julian year to travel a light-year. So there is most likely light beyond what we can currently see because it is so far away. I was under the assumption this was what 'the expanding universe' was but further reading suggests that I am wrong. (As more light reaches us, it would appear that the universe is 'expanding'.)

* The ~ 13 billion year age thrown around is not really the age of the universe, but just the time since the Big Bang singularity. The explanations of the measures of this are somewhat confusing to me. Now, if there is light coming in from further than that number of light years away, wouldn't that mean the universe is older? (I realize that would be impossible to see without a large enough amount of time.)

Thanks. I'll be checking in and out of this thread for a few days and commenting on what you guys say.
gpt
* The expansion of the universe is a metric expansion. Space itself is getting bigger. Because of this 2 non gravitationally bound objects can become separated at speed faster than light can travel. The objects aren't really moving faster than the speed of light, but the space between them is expanding. We illustrate this to undergrads by putting 2 marks on a balloon, as you blow the balloon up the marks are stationary, but the distance between them gets greater, its not a perfect analogy, but it works.

* Due to the expansion of space itself, there are places in the universe that are separated by  a distance that is greater than the speed of light times the age of the universe.