If Hubble’s constant H0 = da/a does not change in time between two times t0 and t, how does the cosmological scale factor a(t) vary between these times? This is from a past exam paper, and being quite honest I don't even know where to start with it. Any help would be appreciated. So far I think the scale factor is supposed to increase, if the hubble's constant is constant. I have tried integrating Hubble's law d(dt)= H0dt between t0 and t but I'm not getting an answer I'm looking for.