Home » News & Blogs » No redshift in a box
Bookmark and Share
Stochastic Scribbles

No redshift in a box

23 Mar 2009, 11:37 UTC
No redshift in a box
(200 words excerpt, click title or image to see full post)

I previously talked about a thought experiment which would supposedly show that “expansion of the universe” is fundamentally different from just “everything moving away from each other”. However, discussion at the Physics Forum has convinced me that light would not be redshifted over time in a perfectly reflecting mirrored box despite the light being [...]I previously talked about a thought experiment which would supposedly show that “expansion of the universe” is fundamentally different from just “everything moving away from each other”. However, discussion at the Physics Forum has convinced me that light would not be redshifted over time in a perfectly reflecting mirrored box despite the light being stretched along with the expansion of space.

Moving walls in comoving coordinates
One way to look at the problem is to realize that in comoving coordinates, the walls of the mirrored box are actually moving towards each other. Comoving coordinates is the coordinate system where the universe is expanding the same way everywhere and in which objects staying “still” observe light being redshifted, and in this coordinate system the walls of the box are actually moving towards each other and causes blueshift in the light, which cancels out the redshift due to ...

Latest Vodcast

Latest Podcast

Advertise PTTU

NASA Picture of the Day

Astronomy Picture of the Day

astronomy_pod