Gravitational Waves

Gravitational Waves

Through an experiment called Advanced Ligo, scientists have recently discovered gravitational wave signals- ripples in the fabric of spacetime. This phenomenon was first predicted a century ago by Albert Einstein. For 75 years, physicists have been working on discovering and proving the existence of gravitational waves. The kinds of instruments they had to use were so precise that they could detect a distortion in space a thousandth the diameter of “one atomic nucleus across a 4km strip of laser beam and mirror”.

The source of gravitational waves come from the collision of two black holes. Scientist used very sensitive detectors and listened for 20 thousandths of a seconds as two black holes, one 35 times the mass of the sun, circled around each other. Through this they learned how starts perish: “the two objects had begun by circling each other 30 times a second. My the end of the 20 millisecond period the two black holes had accelerated to 250 times a second before the final collision and a violent merger took place.

A gravitational wave is the rippling out from a massive collisions- like that between two black holes- that can be detected through the stretching and contracting of space and time.

Professor Alberto Vecchio of the University of Birmingham, pointed out that gravitational waves carry completely different information so they have opened a new way of listening to a broadcast channel .This allows them to discover phenomena they have never seen before. He also stated that this observation marked three milestones in physics: “the direct detection of gravitational waves, the first detection of a binary black hole, and the most convincing evidence to date that nature’s black holes are the objects predicted by Einstein’s theory.”

It only too 20 milliseconds, using the upgraded instrument, to catch the merger of two black holes, at a distance of 1.3 billion light years away. But it took months to check the signal and make sure the evidence matched the theoretical template.  This discovery is a major milestone in both science and history.

How the Ligo system works:

1. A single layer laser beam is split and directed down two identical tubes, 4km long
2. Mirrors reflect the twin beams back to a detector
3. Back inside the detector, the laser beams arrive perfectly aligned
4. Recombines, they cancel each other out
   
   
   
   
   

Detecting Gravity Waves:

1. When spacetime is distorted by a gravity wave, the two tubes change length. One tube stretched as the other contracts over and over until the wave has passed.
2. As the distance fluctuates the peaks and troughs of the two returning laser beams moves in and out of alignment
3. The recombined waves no longer cancel each other out. Light reaches the detector and the gravity wave can be measured