I've watched a video from the American National History Museum entitled The Known Universe.
The video shows a continuous animation zooming out from earth to the entire known universe. It claims to accurately display every star and galaxy mapped so far. At one point in this video [3:00 - 3:15 minutes] it displays this text:
The galaxies we have mapped so far.
The empty areas where we have yet to map.
At this point, the shape of the "universe" is roughly hourglass, with earth at it's centre.
I'm having trouble understanding what this represents and why they shape is hourglass. Is this simply because we have chosen to map in those directions first? Is there a reason astronomers would choose to map in this pattern, or is this something more fundamental about the shape of the universe? Or is it to do with the speed of light reaching us from these distant galaxies?
Continuing on from the hourglass pattern, the cosmic microwave background radiation is represented as a sphere and labelled "Our cosmic horizon in space and time". This doesn't help clear anything up. If we can map CMB in all directions, why have we only mapped galaxies in this hourglass shape.