Univers size conundrum

[gyro]

If we accept the observable universe is 9 billion LY's in any direction and that the Big Bang was 13.7 billion LY's ago and assuming the speed of light is a constant then radiation from early clusters has not reached from horizon to horizon. 9+9=18-13.7 leaves 4.3 LY's.

Will the radiation ever catch up with the expanding universe or have I got this completely wrong.

[Radar]

Hi Gyro,

I don't think so. The universe not only expands at the edges but through it's entirety. So the space between the Sun and other stars is also always expanding. The space between galaxies is always expanding. As the universe gets bigger, there is more expansion from in between, so the edges are pushed out even quicker. At some point radiation from each end can no longer reach the other side no matter how much time is given. This is what I'm led to beleive. What are your thoughts?

Ray

[gyro]

Hi Gyro,I don't think so. The universe not only expands at the edges........................

I agree with your views Radar and had not taken into consideration that light from the first stars was not radiated until 200 million years after the Big Bang. ie, post inflation, by which time the universe was already enormous, but dark. So in a way light has been playing catch up since then. Add to that the recent redshift observations suggest a exponentially expanding universe. I still find it hard to get my head around the concept that the fastest thing in the universe isn't fast enough...If you get what I mean.

[LJF]

You have to remember we don't know exactly where the universe ends. The 9 billion light years in any direction is really just a guess.

[CanisMajorTom]

so what exactly is the diameter of the universe?

Wikipedia states -


The comoving distance from the Earth to the edge of the visible universe (also called cosmic light horizon) is about 46.5 billion light-years in any direction.[4] This defines the comoving radius of the observable universe. The observable universe is thus a sphere with a diameter of 92–94 billion light-years. Since space is roughly flat, this size corresponds to a comoving volume of about



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

[gyro]

so what exactly is the diameter of the universe?

Wikipedia states -



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

Thanks Tom, I keep forgetting to use Wiki :frown: ...I need to do some homework here. the quoted figure for the "observable universe" has thrown me :crazy:

Radar, the second pair of annimations seems to answer my original query...ala your reply.
http://www.phys.ksu.edu/personal/gahs/phys191/horizon.html

[gyro]

You have to remember we don't know exactly where the universe ends. The 9 billion light years in any direction is really just a guess.

I was refering to the "observable universe"...event.... @ 9bly but it seems I was wildly wrong. Join me on Wiki, as per Tom's post, more homework...:frown: :frown: