Cosmic Microwave Background qustion

Why hasn't the light from the CMB already gone by
long ago, since it started out when the universe
was a lot smaller?

The various youtube lectures never answer that for
me.

All of it that remains ought to be long gone,
going the other way, by now. We'd see its
backside, if you could see backsides.
--


On the internet, nobody knows you're a jerk.

Dear Ron Hardin:

On Thursday, June 6, 2013 12:23:14 PM UTC-7, Ron Hardin wrote:
Why hasn't the light from the CMB already gone by
long ago, since it started out when the universe
was a lot smaller?

It was "trapped" at our Rindler horizon.

The various youtube lectures never answer that for
me.

All of it that remains ought to be long gone,
going the other way, by now. We'd see its
backside, if you could see backsides.

Always more salmon swimming up the stream...

http://www.astro.ucla.edu/~wright/photons_outrun.html
.... just remember inflation was multiples of c, and our Rindler horizon (expansion rate at that distance = c) is inside the Universe. Light at that "surface" will take forever to get to us... assuming there is no acceleration of expansion.

David A. Smith

Op donderdag 6 juni 2013 21:23:14 UTC+2 schreef Ron Hardin het volgende:
Why hasn't the light from the CMB already gone by
long ago, since it started out when the universe
was a lot smaller?

Have a look at:
http://users.telenet.be/nicvroom/fri...20equation.htm

You should consider the universe as a sphere and you are
in the centre.
Take a point almost at the rim of the sphere.
Consider this point as an exploding star which emits light
in all directions.
This point will move outwards because the universe expands
however also some light will move towards the center.
Consider this light as a new point as an exploding star which
emits light in all directions.
The difference which this point and the first is that the expansion
difference is less than the first.
The result is that light from the second source (considering the same
time interval) will move more towards the observer. However because
the expanding speed is higher the point will move outwards.
Repeat this many times.
The overall result will be, because the light will move
towards a region where the expansion speed is less that the
expansion velocity becomes equal to the distance travelled
towards the observer at the same time interval.
At this moment the expansion speed is c.
This is the horizontal part in the curve shown.
After that instant the point starts to move towards the
observer because the expansion speed is less than the distance
travelled towards the observer.
This is the blue line in figure 3

Hopes this helps

Nicolaas Vroom