The fraction we see is known as the observable universe. And from what we see, it’s the same. Everywhere we look, there is the same mix of galaxies and empty space, stars and gas clouds. And they all seem to follow the same laws of physics. But we don’t know what’s going on in the rest of the universe – everything beyond the “cosmic horizon” – the limit of our viewing range. Logic suggests that everything beyond this horizon is just like everything in the observable universe. There is no reason why the “bubble” of the universe we inhabit should be any different from the universe as a whole. But we just don’t know for sure – and probably never will. However, scientists can try to draw some conclusions. If they observe a galaxy cluster 10 billion light years away, for example, it has its own observable universe. Some of it overlaps ours, but some extends far beyond it. If the cluster is being pulled toward the region we can’t see, then scientists might conclude that it has been dragged by the gravity of something big and heavy—perhaps a giant galaxy cluster far outside the observable universe—something we’ll never see. . Screenplay: Damond Benningfield
