The Universe is expanding at 74.2 km/sec/Mpc

How far away are things? That is perhaps the most basic question in astronomy, and in some ways the most aggravating. For nearby stuff -- and by that I mean everything from the Moon out to stars about 1000 light years away -- we can measure distances directly. Bouncing radar pulses off of planets gives us their distance, and in some cases we've sent probes to them so their distances are extremely well known. For nearby stars we can use parallax, which is using the motion of the Earth around the Sun to see how that affects how we see the position of the stars in the sky. But for distant galaxies, getting their 10-20 is a lot harder. That's why objects like the spiral galaxy NGC 3021 are so useful: