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So, an interferometer is the instrument used to measure gravitational waves. But, how do they do it? Well, the interferometer is an ingenious invention created by Albert Michelson back in the 1880s. The concept is actually quite simple too. The design starts with a concentrated laser beam, like any good invention. Next, the laser beam hits a beam-splitting mirror at a 45 degree angle. Thus, half the beam travels straight through the mirror, and the other half is deflected at a 90 degree angle. Each beam separately travels down several mile long corridors to hit a solid mirror, and bounce directly back. Once the beams again meet up at the beam-splitting mirror they collide in perfectly opposite tandem, crests meet troughs, and the two laser halves destroy each other. Wait... so then how does it measure a gravitational wave? Well, don't forget, these waves actually bend space-time. And, they do it cyclically, with one direction stretching while the other shrinks, and then swapping. So, when they meet the interferometer, they actually elongate one of the corridors, while shrinking the other. This shifts the laser out of phase, and the two halves no longer cancel perfectly. Thus, the now undistorted laser recombines in the beam-splitting mirror and continue on to hit a photosensitive device. However, gravitational waves oscillate, so the end result actually comes up as a strobe light. Scientists then take this flashing light in as data with a computer, and transfer it into sound waves to be more easily understood. After all that work, one of the most powerful events in the universe is finally reduced to a small beep. It is exactly this beep which scientists at the Advanced LIGO observatory heard on September 14, 2015 at 5:51 am. Now, even more observatories are being put up all over the world in order to gain more accurate readings of these outlandish events. The soonest completed may be a new LIGO in India, and with this new observatory there will certainly be more gravitational wave sightings to come. With any luck, this outstanding discovery will lead to some excellent quantum mechanics and origin of the universe realizations.
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!
There's been a good deal of hype surrounding gravitational waves recently. It's been all over the news, and has something to do with Einstein as far as we know. Wondering what it all means? Well wonder no more, I'm here to deliver the abridged version of what you need to know! For dummies. So, what is a gravitational wave? Well, it's a wave that propagates through space-time itself. Remember how space and time are actually one thing, like a quilt over the universe? Well, gravitational waves travel along that plane, stretching and shrinking space itself. And, it acts upon space-time in perpendicular directions, kind of like an electromagnetic wave. In short, it's a transverse wave (think of a sine wave) that acts in two different directions, the horizontal and the vertical. Now, that may still be confusing, so imagine this. You're standing at the end of a long square hallway with lights all along it. A gravitational wave starts at the other end, traveling toward you, and means business. As it approaches you, you would see the walls and ceiling of the hallway bending in and then puffing out rhythmically. As the walls puff out like they're being pushed in the center, the ceiling and floor get sucked in towards the center of the cross sectional hallway like someone pulled in the middle. Then, the two pairs of sides switch, and the ceiling/floor puffs out while the walls get sucked in. It travels closer and closer towards you, pushing and pulling in time, until it reaches you. At this point it crushes your arms into your torso, rips your head and legs off, then switches and stuffs the top and bottom back on like a hastily saved muffin and pulls your fingers off. Rude. But, that doesn't mean gravitational waves aren't cool! Check out part two for some more in-depth understanding now that you know what gravitational waves look and feel like!