The obvious question to ask is if matter didn't, doesn't and will never travel faster than the speed of light, what generated the echoes..>:)Of course, after the two cross-sections shown above, there shouldn't be any doubt that the Big Bang generated NO ECHOES...:) There isn't any wall just outside space...:)
If you think about my proposed Cosmogenesis where the Big Bang is the result of the decomposition (with incomplete reassimilation) of a dipolar (or multipolar) metric deformation of a 4D Spatial Manifold..:) then you will realize that the circle corresponds to our 3D Universe.
You should also realize the symmetry associated with a circle. The Big Bang occurred on all points of that circle at the same time...:) As the circle expanded, light from one radian would always reach you no matter where you look at.
That obvious symmetry also explains in a trivial manner why the temperature of different points of the Universe are the same...:) No BS or Inflation of any sort is necessary...:)
Since one radian corresponds to a region of space traveling alway from you at the speed of light, you will never see exactly the Big Bang, but you will be able to see that light coming from its neighborhood. That light (Gamma Radiation) will be shifted into the microwave region and form the Microwave Cosmic Background...
History Channel is playing again a show about those Echoes.. .and you know that makes my blood boil...:) so I had to challenge Pebbles to take the opposing position...:) Brian Greene would be also welcome to respond to this...:) Or Alan Guth...:)