# Viewing a far away galaxy through a wormhole

1. May 3, 2012

### NWH

Hypothetically speaking of course, if we were to observe a galaxy billions of light years away on the opposite end of the universe through a wormhole, what would the red shift look like compared to other galaxies in the observable universe? For example, I'll set up a thought experiment.

We have two galaxies, galaxy A and galaxy B. Both galaxies are at the same distance away in the the farthest reaches of the observable universe, both have the exact same brightness and both are traveling at the exact same velocity. Galaxy A is on the left, galaxy B is on the right, however in front of galaxy A we have an open wormhole like a looking glass giving us a closer look at that galaxy. What would we see in the red shift? How would the red shift differ between galaxy A and galaxy B?

2. May 11, 2012

### clamtrox

It depends on what kind of wormhole you are thinking about. Redshift is caused by space curving along the light beam, so in principle you would see less redshift. However you have to remember that wormholes are crazy curved themselves, so all bets are off unless you give me the precise form of it.

3. May 13, 2012

### HarryRool

Bracketed insertions mine.

The frequency shift of light from galaxy A could range from being extremely red, to zero, to extremely blue. It depends on the motion of the wormhole mouths. A course, light from galaxy B would have the usual Hubble redshift.

Suppose that the wormhole mouth near Earth is approximately stationary relative to Earth. Then the frequency shift depends on the motion of the far mouth (the one nearer to galaxy A) relative to galaxy A.

If the far mouth is receding from galaxy A: redshift
If the far mouth is stationary relative to galaxy A: no frequency shift.
If the far mouth is approaching galaxy A: blue shift.

This ignores any frequency shifts due the wormhole's gravity, which would depend on the particular characteristics of the wormhole.