Why is the universe expanding?
A) The energy from all the stars is heating the universe, making it expand like a gas that is heated.
B) Spacetime itself is expanding, carrying the galaxies (or superclusters of galaxies) with it.
C) The universe is not expanding-it is the Galaxy that is getting smaller, making the universe seem bigger and bigger.
D) An infinitely dense clump of matter exploded, sending the galaxies (or superclusters of galaxies) hurtling out through space.

Question

Quizplus · Accepted Answer

The expansion of the universe is best described by the expansion of spacetime itself, as per the theory of general relativity. This expansion is not due to the galaxies moving through space by their own momentum (as might be implied by an explosion) but rather because the fabric of space in which they reside is expanding.

Why Is the Universe Expanding