Originally Posted by hat
The way I always thought it worked was that empty space is infinite, and the expanding space is objects drifting further apart from each other.
current data suggests that the universe is flat, there is a certain amount of measuring error, which could mean that the universe is just really really big, so the local curvature we see is too small to detect it (like the earth looks flat to you).
expanding universe means the space _between_ galaxies expands. objects that are gravitationally bound like our whole galaxy, the atoms of the earth, the atoms in your body, their electrons, do not move apart from each other.
a popular example to illustrate expanding universe is a balloon with dots painted on it (galaxies), and the balloon gets inflated, so the space between all points expands. a more accurate representation would be to glue some colored paper dots on it (so those won't expand)