Considering that the more distant an object is the smaller the angle it will make why would parallax measurements be better suited for stars than for galaxies?
Galaxies are considerably farther away than the stars in our galaxy.
Depending upon how distant the galaxies are, in some cases it takes light billions of years to reach our planet from distant galaxies, which means that we are not seeing those galaxies as they are now, but we are instead seeing them as they were, billions of years ago. The more distant a galaxy is, the longer it takes for its light to reach us, and therefore the earlier the galaxy that we are observing.
We can't run a measuring tape out to the nearer stars, and it would take too long to bounce a radar pulse off of them (even if it would work!) so we have to use other, less precise measurements. For "nearby" stars - less than a couple hundred light years or so - we can measure their parallax. We take an observation of a nearby star and note the very distant background stars. We repeat…
Explain why looking at distant galaxies gives scientists an idea about how galaxies change over time?
The light of those distant stars and galaxies took an appreciable period of time in getting here to be detected in our telescopes. So when we look at distant galaxies, we're seeing the light that those galaxies emitted thousands, millions or BILLIONS of years ago. So it almost is like looking back in time.
The further something is away form us the longer the light from it has been travelling to reach us. Thus when we look at very distant objects (galaxies) we see them as they were in the distant past when they were young. The more distant they are the younger/earlier they are. This effect is enhanced by the expansion of the universe which also makes the light from distant objects shift towards the red end of…