The cosmic microwave background radiation is the furthest and oldest visible light in the universe. But the universe has expanded considerably since that light was emitted. At the time that that light was emitted, how big was the “thing” that emitted that light? Was it bigger than, say, the Milky Way?
And, how should I conceptualize the object? I imagine it as a growing sphere of light, but that presumed that it was expanding into something… But since (perhaps?) this thing was space itself, then maybe it doesn’t have a surface. Could it nevertheless be described as a finite volume, just, perhaps one without a boundary? And if so, how on earth do I visualize that?
