Why Quasars

Throughout history, mankind has used the stars for navigation and to study the earth. Unfortunately, using nearby stars in our galaxy has limitations. First of all, the earths atmosphere refracts light in unpredictable ways. This limits our ability to precisely position any star. Secondly, all the stars visible to us are not fixed in space. They're all moving in different directions and, worse than that, they're moving at different speeds. Trying to accurately position a point on earth using moving stars is sort of like trying to position yourself on a boat by using all the other moving boats out on the water. Talk about a tough task. What we need instead of other boats, is a fixed point on the shore to use as a beacon. Quasars are the 'beacons' we can use to position ourselves in the Universe.

How does a Quasar act as a beacon?

First of all, because the radio waves from quasars are virtually unaffected by atmospheric refraction, we can determine their position very precisely. Secondly, quasars are really, really, really far away. I mean really far. Quasars are the farthest known things in the Universe. Energy from a quasar can take 10 to 15 billion years to reach the Earth's atmosphere. Quasars are so far away that they don't appear to move. Ever. So, because they never move, and we can determine their position very well, quasars have proved to be very reliable 'beacons in the sky'. Not only that, but because quasars are scattered in all directions and since radio signals are unaffected by our atmosphere, quasars are a very convenient way to position ourselves in the Universe, day or night, rain or shine and can be observed from all around the world.