The existence of gravitational waves was first hypothesised in Einstein’s Theory of General Relativity, but this was never proved at the time. On the 11th February 2016 physicists announced the breakthrough of the century, the discovery of gravitational waves! The first detection of the waves happened at the Laser Interferometer Gravitational-Wave Observatory (LIGO) when two of their instruments detected an interference that lasted one ten thousandth of second. The mystery is finally solved, Einstein was right, and gravitational waves are real.
So what is the Theory of General Relativity?
Albert Einstein stated that every mass distorts both space and time (and that they are in essence the same) in the same way a ball would distort a trampoline. Empty space-time is “flat”, whereas space-time in the presence of masses is curved. The deformation in the space-time system, produced by masses is called curvature.
What is a Gravitational Wave?
Gravitational waves are the ripples formed by violent impacts between very dense bodies, such as neutron stars or black holes, travelling at the speed of light. When gravitational waves travel, they create a slight distortion in one region of space which, in turn, distorts the nearby regions, until the energy disperses and they become so weak that they cannot be perceived any more.
What did the instruments detect?
The interferometers which detected the waves are formed by two light beams travelling between pairs of mirrors along pipes running in different directions at right angles to each other, such as north and west. If a gravitational wave goes past the system, it stretches space in one direction and shrinks it other. On Earth, that caused the mirrors in the instruments to swing tiny amounts, so that the distance between one pair of mirrors got smaller, while the other got larger. The swinging is the mirrors responding to the stretching and compression of space-time.
The gravitational waves detected were produced by the fusion of two black holes, with masses approximately 30 times larger than our Sun, about 1.5 billion years ago. When the holes became closer to each other, they started spinning faster and faster. The result was a huge black hole with a mass of 62 suns and the energy which was released in the form of gravitational waves has been travelling across the Universe since then, and when those waves affect Earth we are able to detect them.
What does this mean?
Prof. Alberto Vecchio, professor at the University of Birmingham and researcher at LIGO, said “Gravitational waves carry completely different information about phenomena in the universe”. Until now, the cosmos has been studied through the light radiated by stars, galaxies and other celestial objects, which emit electromagnetic waves. Through gravitational waves we are also able to “hear” it and we can study parts of the universe that we can’t directly see. For instance, black holes do not reflect light but gravity can still escape from them. As a result, gravitational waves can tell us significantly more about black holes than light can.
But what does this actually mean?
According to the Big Bang theory, after the primordial explosion, the Universe was a huge amount of matter concentrated in a very small space, this quickly started expanding, and evidence based on observation of light suggest that it is still expanding. Now, as we go back in space, we also go back in time, since the furthest matter is also the oldest (so the further away we look the further back in time we look). The gravitational waves produced by the massive explosion of the Big Bang 14.5 billion years ago, we are now able to look for, allowing scientists to go back in both space and time to look for information giving the final answer to the oldest question ever: how did the Universe get here?
So can we travel back in time?
In terms of seeing the start of the Universe yes we can!
But does this mean that I will be able to time travel?
We’re closer to that possibility that we ever have been before!