So, now that you know what gravitational waves are, where do they come from? Well, they are generated from some of the most energetic processes in the known universe. This includes supernovas (like the Big Bang), neutron star collisions, Black Hole mergers, etc. In actuality, gravitational waves can occur any time masses accelerate in non-symmetrical motion. However, the only detectible sources are the ones listed above. Even these events are often incredibly difficult to detect, since the waves diminish to near unnoticeable levels by the time they reach Earth (thank goodness too, remember that head and arms thing from the last post? uugh). Though, gravitational waves themselves can actually have amplitudes larger than the universe.
Gravitational waves were first proposed by Albert Einstein in 1916 as part of his theory of relativity. So, I guess it only took us a century to match his intellect, high five! Anyway, they also refute one of Newton's assertions in the Newtonian theory of gravitation, since Newton postulated that physical interactions propagate at infinite speeds. In reality, gravitational waves only travel at the speed of light, which isn't even as fast as some kids drive to school in the morning. But, what's really interesting about gravitational waves is that they actually tell a lot about the events from which they occurred. For example, the waves first detected were from the merging of two black holes. With multiple interferometers - the instruments used to measure gravitational waves - you can even triangulate the position the waves originated from. Scientists are currently hoping to use information gleaned from the study of gravitational waves in order to gain insight into the Big Bang and the ever elusive dark matter.
Though, like i mentioned earlier, they're incredibly small by the time they reach Earth. So minute in fact, that Einstein thought that humanity would never be able to measure one. Einstein: 1, U.S.: 1. Thankfully, we have a really cool instrument for measuring them. Check in for part 3 to get the full scoop!