Originally Posted by omegaman
Bare with me…
Okay, lets suspend the concept of General Relativity for moment. If the universe was totally empty and suddenly a 1 metre cube of solid steel mysteriously appeared from nothing at the very centre of the universe, it would neither be floating nor moving, just existing in a vast vacuum, right? Suspended there by nothing, right?
The answer would then be inertia.
You have too elements in this experiment. A universe (which we presume is expanding because their is a passage of time. The other element is the Steel Cube.
We don't understand exactly why (that's what the Higgs Boson & Field is all about) But matter resist the expansion of the universe. The universe is pulling on the Steel Cube but the cube refuses to move as fast as the universe. Plus since there is nothing else it means the universe is pulling on the could equally (more or less) from all sides. If the Cube were energy it would move right along with the expansion of the universe like an explosion.
But matter is different.
Not only does matter cause itself to move slower it also makes the universe immediately around the Cube move slower which makes time move slower.