On 11 February 2016, Executive Director of LIGO (Laser Interferometer Gravitational-Wave Observatory, one of the most sensitive detectors in US) David Reitze, in a recorded statement made the announcement that they have positive evidence of having heard the presence of a minute gravitational waves caused by spiraling two black holes 1.3 billion light years away from Earth. They also said that this confirmed one of Einstein’s predictions as a result of his own General theory of relativity a century ago. A team of over 1,000 researchers from 15 countries, led by scientists at the Caltech and MIT, published their work in Journal of Physical Review Letters.
Physicist Dr Robbert Dijkgraaf, director of the Institute for Advanced Study in Princeton, N.J., where Einstein himself once worked said, “They picked up this minute tremble in space, but it is totally shaking up the field of science”. He added, “It is confirming the ideas of one of the most brilliant minds that ever lived”.
However, this significant detection is the not the first of its kind. In 1993, two Princeton University researchers Russell A. Hulse and Joseph H. Taylor Jr won the Nobel Prize for their discovery of an unusual pulsar star that offered indirect evidence of gravitational waves. Again, in 2014, astronomers at the Harvard-Smithsonian Center for Astrophysics thought that they have spotted gravitational waves but very soon they went back to their labs saying they haven’t, yet.
Now, we know something of the world famous icon of the theoretical physicists Albert Einstein, but what are these gravitational waves and why it matter so much to the world? Let’s try to understand.
Einstein, the genius, as the world knows him today, is known largely due to the two scientific papers he had published. One, Special theory of relativity in 1905, which redefined the way scientists understood the notion of space and time forever, and second, the General theory of relativity (= Special theory + gravity) that came out in 1915 and changed the way scientists understood gravity as well.
Until now, gravity to the world was as told by Newton. But Einstein’s general relativity theory does not agree with the Newton’s theory of gravity where gravity is the force of attraction between two massive objects. In Einstein’s world, gravity is the result of the bending of space time curvature due to a massive object. The two objects are attracted towards each other, and look like revolving around each other, due to this dent in the curvature. In other words, the lighter object moves more rapidly towards the heavier one, thus giving rise to an allusion that it is actually revolving around the massive one. In the same way, all planets revolve around the Sun due to the mass of the Sun creating the dent in the space-time curvature around it. Since the massive objects also move in the space-time – the curvature changes to reflect the changed locations of those objects and hence the allusion of one object revolving around each other (and not eventually collapsing into it) sustains.
Further, the more the mass of the object, the more the dent in the curvature and hence the farther the gravitation effect it will pose on distanced planets and objects in the universe. Now, if the object is even more massive and accelerating too, the curvature in the space-time that it creates will propagate as well. These propagating phenomena are known as gravitational waves.
— BBC Science News (@BBCScienceNews) February 15, 2016
By Einstein’s reasoning, any object with mass, such as black holes or binary neutron stars, could warp the curvature of space and time, like a bowling ball on a trampoline, stirring the fabric and generating waves that radiate at the speed of light. And wherever these waves go, they will affect the movement of the objects in their path, just like the curvature keeps the smaller object rotating.
Now in physics terms, it is extremely difficult to measure the changed movement of object due to these waves. But just as we can measure the displacement of water in water body, we can measure the displacement of something that is not massive and yet should be displaced – the Light.
The LIGO detectors measure how long it takes for controlled laser light to travel between two of its suspended mirrors. If Space time is rippled, the distance measured by the light beam will change causing the amount of light falling on the LIGO photodetectors to vary infinitesimally. This displacement of LASER detected by LIGO can confirm the presence of such waves being sent out to Earth.
(The sound of these waved can be heard here: http://nyti.ms/1Pz5kE6)
For the scientists and the astronomical world at large, the consequences are immense and astounding. Since G-Waves are largely unimpeded by matter, they can reach places where EM waves cannot. A lot of events in the universe must be sending these waves out owing to the very nature that the entire universe is actually seen as a space-time fabric- with Earth as well just an object in its course. And since now we know that they exist and we know how to detect them successfully – we now have a ‘google map’ to unknown areas of the universe which are not yet accessible but could be sending out ‘we exist’ signals to us in the form of these waves.
But what lies in it for the common man, other than the excitement to have the possibility to know the other far sides of the universe?
To answer this question, we may have to study Einstein’s mind more than his theories, or for that matter, the mind of any scientist who assumes that exploring nature and understanding our universe without any end to it can be a fulfilling end in itself.
Einstein was never awarded the Nobel prize for any of his Relativity theory but for other great inventions that he did, including the photoelectric effect, which has the potential to change the lives of millions in a more potent and visible way. From a student who never enjoyed studying humanities subjects at school to a true humanist who would turn down the offer to become Israel President in order not to give any less importance to the more objective work at hand – Physics, Einstein eventually saw the universe as something that must be explored and explained and saw such theories as something that contains ‘the thoughts of God’. Einstein was the man who found peace only in two things in his life, working on the grand unified theory after late 30s till the end of his life (although it did gave him nightmares too) and music, being a good violin player himself.
But what caused Einstein to think so much ahead of his time and imagine things that weren’t there even in the wildest imaginations of the most celebrated scientists of his time, baffles cognitive scientists and neuro-biologists equally until today. Was it the extra packed part of his brain (that is still lying half cut in New Jersey, logically undefeated) or was it just a highly God-gifted mind, who knows? Not only a genius, but the confidence of Einstein over his theories was very immense. This cannot be better asserted than this anecdote that when he was asked once how he’d feel if relativity, and that the consequence of space as seen as the curve that could cause bending of starlight around the sun was disproved by the eclipse experiment that astronomers undertook in 1919 solar eclipse, Einstein famously replied: “Then I would feel sorry for the dear Lord. The theory is correct anyway.”
To Einstein’s most profound general relativity theory’s consequence – gravitational wave, an idea Einstein himself doubted (more or less like Quantum physics), detected using LASER (a discovery that uses Einstein’s another idea only – stimulated emission), well, honestly, I don’t know of any other ‘seriously charming’ way that irony can possibly have, to play with geniuses even long after they are gone.
We probably have to wait for a few more centuries before Science becomes just as popular and intriguing to us, the common man, as Albert Einstein was to Science itself.