Albert Einstein’s theory of general relativity has been proven right again.
As Einstein predicted in 1916 in his General Relativity we have observed ‘ripples’ in the fabric of space-time caused by some massive accelerated objects in far away from earth.
On September 14, 2015 Laser Interferometer Gravitational-wave Observatory (LIGO) heard the sound of two black holes
Where did this sound come from?
From a long time ago in the distant part of the universe two black holes, each about 30 times as
massive as our Sun were locked in orbit. After that it started spiraling in towards each other, the only visible traces of the spinning cataclysm would have been the way their gravitational fields warp the light of distant stars. Even as they collided emerged, there wasn’t a flicker of light to be seen.
But one thing happen the real and very violent action in the system was in the form of gravitational waves ripples in the very fabric of space and time. These waves were constantly draining energy from both the black holes, orbits leading to the ultimate collision and merger to form a single black hole.
At that instant which they were merged the power of the gravitational waves was 50 times greater than that of all the stars in the universe combined.
That pulse of gravitational waves lasting only a fraction of a second and expanded through the universe passing unimpeded through countless galaxies.
It took about 1.3 billion years to reach the earth gravitational waves alternately stretched and squeezed space itself and everything they pass through. Even thought the collision is massive the effect is minuscule. To detect them and directly measure their properties scientists build LIGO the most sensitive measuring device ever made.
LIGO uses a device known as an interferometer to measure the tiny displacements in space.
A laser beam is sent towards a partially reflecting mirror and split along two paths the beams travel along the four kilometer arms and reflect back towards the central mirror which we combines them directing their light to a detector. As the gravitational wave passes the distance between the central beam splitter at the end mirrors stretches along one arm and compresses along the other.
This changes the time it takes the light to travel along the arms. The recombine light wave shift with respect to one another and produce a signal at the detector incredibly tiny stretching and squeezing of space can actually be measured directly in this way.
How little this space to store to make this signal?
Let’s think about a hydrogen atom, until we reach the proton that its core.
LIGO is so sensitive it can measure changes in distance as tiny as a thousand to the diameter of a proton. And this tiny measurement made by ligo was
the final step in a journey that began 1.3 billion years ago in the distant universe when two black holes collided.