APOD: Microwave Milky Way (2010 Jul 09)

[bystander]

Actually, the Microwave Background Radiation is NOT 13.7 billion light years distant. The radiation was captured by the Planck telescope. That means it is here. The radiation originated 13.7 billion years ago, but it can't be 13.7 billion years distant. We wouldn't be able to see it. This is kind of like saying when you take an image of the Andromeda Galaxy, M31, the light is 2.2 million light years distant. The galaxy is 2.2 million light years distant, but the light has to be in your telescope and in the CCD camera in order to see it.

Yes, the radiation probably should have been left off. the radiation is here, but the CMB is still there, but not 13.7 billion ly, more like 46.5 billion ly, the comoving distance to the edge of the observable universe.

[Case]

the radiation is here, but the CMB is still there, but not 13.7 billion ly, more like 46.5 billion ly, the comoving distance to the edge of the observable universe.

By the Cosmological Principle, the CMB is everywhere, both here and far away.

[Chris Peterson]

Yes, the radiation probably should have been left off. the radiation is here, but the CMB is still there, but not 13.7 billion ly, more like 46.5 billion ly, the comoving distance to the edge of the observable universe.

The radiation is the CMB. There is nothing out there at 46.5 billion ly any different than what is right here. When we observe a photon that is part of the CMB, all we can say is that the piece of the Universe that emitted it is now 46.5 billion ly from us. Any observer at that point would be recording CMB photons that originated from our position.