At what scale is the universe expanding? Homework help?

Question

The choices are:

Interatomic- space between atoms is growing
Interplanetary-space between planets is growing
Interstellar-space between stars is growing
Intergalactic-space between glaxies is growing

Answer 1

Also, a very important recent discovery is that the rate of expansion of the universe is actually increasing. So not only is the universe expanding, it is expanding faster all the time.

There used to be conjecture that the expansion would slow down and the universe would start to collapse again followed by another big band then another expansion and so on. Looks like that won't be happening. It appears that the universe will just expand indefinitely! More research is needed to confirm this and discover why.

Answer 2

Space between gravitationally bound objects isn't growing. So the local group of galaxies which includes us, M31 (Andromeda) and the Magellanic clouds stays together, as do closer groups of objects like the solar system. But the Virgo cluster of galaxies and more distant objects are all moving away from us. The constant is Hubble's constant; about 75 km/sec per megaparsec. So an object 1 MPc is moving away from us at 75 km/sec.

Answer 3

The best answer there is 'intergalactic`,
but even there gravity still binds 'local groups`,
(as 'Zee..` points out), at least for now.