On: Why Is Light So Fast?

[whamlastxmas]

Something to do with the universe expanding faster than gravity could ever hope to pull things together right?

[nojvek → whamlastxmas]

Also we don’t know why the universe is expanding. Not just expanding but accelerating. Why is spacetime itself stretching and what is doing it?

Yeah yeah dark matter blah blah, but it’s not a concise enough answer.

[david-gpu → nojvek]

Dark matter doesn't make the universe expand. It is massive, and thus it brings things together.

Dark energy, on the other hand, is the postulated cause of the expansion of the universe.

Edit: not a Physicist!