redshift - Are we center of universe?

At the time when the universe was ~380,000 years old it was completely filled with a plasma and light. Light could only travel very short distances (I forget the specifics, but think a couple meters at the most) before being absorbed. So the entire universe was a fog, if you were there and there was an object 10 meters in front of you, you couldn't see it because all the light it emitted or reflected would be reabsorbed before it reaches your eyes. There are two things to keep in mind: 1) This fog disappeared across the entire universe simultaneously (plus or minus some time, but effectively simultaneously); at the same point in time after the Big Bang, 380,000 years after the Big Bang, the fog dissipated due to recombination. And 2) Light takes time to travel.

So let's say you are sitting in the fog-filled universe a few seconds before recombination happens. Light travels about 1 foot per nanosecond. So if the fog disappeared and there was a street lamp 10 feet in front of you, you wouldn't receive the first light from that lamp for 10 nano seconds. All of the light the lamp was emitting before recombination was just reabsorbed, but after recombination the first photons to leave the lamp no longer have anything to run into, so they continue on until hitting your eyes. A street lamp 20 feet away wouldn't be visible for 20 nanoseconds after recombination. The light of the plasma itself is effectively a street lamp at every location in space, so due to the 2 facts above, you would see successively farther street lamps in a shell centered on you.

After recombination happened and the entire universe became transparent. The fog is gone, but the farther you look the farther back in time you look, so you can only see back as far as when the fog existed, and the farthest you can see is the fog itself. After 13.8 billion years you can see all the way out to a shell of radius 13.8 billion light years around you (ignore expansion of the universe for now), and what you see is the light of the plasma (the fog) that was filling the universe 13.8 billion years ago, the CMB.

This scenario is the same if the universe is infinite in extent. We are not the center of the universe, we are simply the center of the observable universe, as is anyone else. Aliens looking towards Earth but are at the current location of edge of the CMB in some direction will not see Earth, they will see the last light of the CMB itself at our location when it was emitted 13.8 billion years ago; we are the edge of their observable universe.