Gravitational Waves.
The Idea of a Gravitational wave.
Consider the following situation, you and a friend are standing on a trampoline at the edges, if you look down you see that you form sort of a depression in the area around your feet and the same goes for your friend. Now you both hold each others hand and start hopping around on the trampoline in a circle, you would notice that the trampoline would produce some sort of a wave motion. The same goes for Gravity.
Except that you would be a planet or any other massive object which would distort space around you. This depression would actually attract more bodies towards you. Lets say that one of the bodies tries to move in a straight line around you, what would you get? A circle or an ellipse which explains how planets move around the sun.
When you get two really massive bodies orbiting each other like a binary system of a black holes, the fabric of space time would also move in a similar fashion to you and your friend on a trampoline, only on a much much larger scale.
So these waves caused by the motion of the bodies in the fabric of Space-Time due to gravity are called GRAVITATIONAL WAVES! Its is basically a ripple in Space Time.
There is more to this though....Einstein said this in his principle of General Relativity That gravity acted as a warp of space time around the object. Any two bodies in the fabric of space time would create a wave like disturbance which would create a Gravitational wave.
However there is one catch, gravitation is on of the weakest forces compared to forces like the strong nuclear force which holds atoms together. So you need really massive objects to create DETECTABLE Gravitational Waves like Collision of two Neutron Stars (Check out my Post on Some of the Universes Weirdest stars HERE)
How Do You Even Detect a Gravitational Wave?
That's is the tricky part, unlike the trampoline where you and your friend can feel the disturbance, Gravitational Waves don't behave the same way. Gravitational Waves ripple back and forth thus increasing the distance and decreasing the distance between two bodies.
Just imagine you trying to measure the distance between you and your friend in the water in a Swimming pool. Since the water is mostly still, given that you don't move much you can measure the distance between you and your friend with no problems.
But measuring Gravitational waves is a different story.
Imagine that now you and your friend are standing in the ocean. Since the water forms waves now you and your friend would be moving back and forth between each other. Measuring the distance between you two with the surface of the water is stupid!
Even if you guys were on dry land and you stood 5 meters or 16 feet away from each other and placed 5 rocks on the ground at a distance of one meter or 3.26 feet from each other, you wouldn't notice the distance between the rocks changing!
Gravitational waves work in a similar way because the expand and contract the space around you and your friend. They are usually caused by two massive bodies slamming into each other.
How did the Scientists at LIGO measure it then?
If you cant measure the distance between 2 places because the ground/space between them shrinks and expands due to some Funky Gravitational Waves, How do you measure it? Simple use another wave and lucky for us this wave or Electro-magnetic Pulse travels at the same speed where ever you go! LIGHT!
Since light travels at the same speed everywhere in the Universe you can measure the change in the distance of two places in space.
Lets say I stand at on corner of a room and you stand at the other holding a mirror. I keep flashing a laser pointer at the mirror and record how much time it takes for the light to reach back to me.
If the space between us were to increase due to a disturbance caused by a gravitational wave, light from my pointer would take a little bit longer to reach me. If the distance decreased however the time taken for the light to reach me would be less.
How Does The LIGO work?
The LIGO stands for the Laser Interferometer Gravitational Wave Observatory, which by the way you can call GIANT LASER RULER (Cool, eh?). As I explained above the LIGO measures these tiny tiny intervals of time for light to be emitted and reflected back to the source. It has 2 long arms stretching 4 kilometers / 2.4 miles on each side at right angles.
The lasers measure the changes in the length of these 2 tunnels. Now when a Gravitational wave passes through it squeezes space in one direction and expands it in the other. By measuring the interference between the two points using the lasers we can measure whether the space in between stretched or compressed.
How accurate is this AWESOME LASER ruler I hear you ask?
This Detector is so accurate that it could measure a change in the length of a stick 1,000,000,000,000,000,000,000 meters (1 SEXTILLION : One followed by 21 Zeroes) by 5 millimetres!
Since Gravity is pretty weak and the waves caused by it are even more, these waves can often be masked by other random noises in the universe such as cosmic radiation and other microwave background. So to over come this problem, we had to have a smart data analysing software which separated these "random" noises.
They compared all these waves to a theoretical model of what a Gravitational wave looked like and they indeed found one.
Two black holes orbiting each other collided resulting in a Gravitational Wave! On September 14 2015 9:50 UTC LIGO caught such a wave and after a lot of analysis we found the first Gravitational Wave! (Watch Doc Schuster's video on it)
This is a completely new way of studying general relativity and whenever science finds a new way of doing something, we discover something new.....
Click HERE to listen to the Chirp made by the collision of two black holes!
Leave a comment below telling me how you liked this topic! Any suggestions and new topics are welcome too!
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