The Universe Speaks to Us in Music – Physicist Explain Gravitational Waves and their importance

September 2015 peaked in Louisiana, with the inauguration of a new and very sensitive optical device, which was part of an experiment at the Laser Interferometer Gravitational-Wave Observatory (LIGO), aimed at helping physicists detect distortions in space and time. Scientists have long been trying to prove Einstein’s predictions about the structure of the universe, since his theory of general relativity was published over a century ago, and many have succeeded. Yet, one prediction remained a riddle – the existence of gravitational waves. In layman terms, Einstein predicted that the motion of massive bodies in space creates waves in space-time, which ripple out and shape the structure of the universe. The new LIGO sensors should be able to identify these wavy vibrations, and tell us about cataclysmic events that took place over the course of the universe’s history.

Some 1.3 billion years ago, somewhere out there is space, such an event had occurred on a massive scale. A pair of black holes became interlocked in a spiral around each other – until they clashed and merged into one black hole. This collision released so much energy, “50 times greater than the output of all the stars in the universe combined”, the NY Times reports. It sent gravitational shockwaves that have been spreading across the universe ever since, for billions of years. On September 14, only two days after the new LIGO sensors were officially launched, these waves suddenly arrived on Earth and were detected by the brand-new sensors.

Although we are, after all, talking about science, the fact that these sensors became operational at that particular time is somewhat of a miracle. Researchers have been trying to capture the gravitational waves since 1993, but to no avail. And now, fate must have stepped in, and these waves just happened to pass through two days after we had the specific technology designed to identify them. Over the cosmic timeline, they may appear to be marginal, but for us here on Earth, they are immensely critical. Who knows when other such gravitational waves will pass through here again, and if by then we would even be here to identify them?

The music of the world

Actually, gravitational waves are not such a rare phenomenon. Every time we move, we create gravitational waves, but they are too faint to be noticeable. Unlike us puny humans, objects the size of the sun create gravitational waves that impact space and time across immense distances, forming curved paths for stars and planets to orbit around them, like the Earth does. Imagine the ripples of a leaf that falls on water, as opposed to the effect of a huge meteorite crashing into the ocean. Why does this happen? Let’s say that the structure of the universe is a flat, elastic fabric. If you were to place a ball on it, it would distort and curve the fabric downwards, around the ball. If you were to then roll some smaller balls nearby, they would be caught within this downward distortion, and be pulled towards the larger ball, in a curved path that orbits around it. That’s exactly the way the sun’s gravitational waves hold the Earth in motion, revolving around it, and this enables the unique relationship that exists between these celestial bodies. In some way, gravitational waves play a fundamental role in creating the conditions needed for life, which depends on the sun’s energy.

The dramatic event of the two black holes colliding together had occurred more than a billion years ago, and the distortion it created in the fabric of the universe has since travelled an endless journey before passing through Earth. At this point, the waves have become so faint that only a highly sensitive device can detect them, able to identify changes in oscillations that are the size of a fraction of an atom’s proton, within the entire structure of reality. Fortunately, such a device had begun operating a mere two days prior to the passing of the gravitational waves through Earth, at a cost of millions of dollars allocated for this purpose precisely. The distortion that these gravitational waves created is so minute, because the blast of energy had only occurred for a millisecond when the two black holes merged. Moreover, gravity – as much as it dominates our existence entirely – is actually considered to be a relatively weaker force in nature, compared with the other natural forces at work. Add this factor to the waves already becoming weaker after traveling across endless distances and time, and you can see why the most sensitive device is needed to capture their delicate signal.

LIGO is able to identify the changes in the structure of reality using rays of light. The principle is simple. A laser beam is shot at a semitransparent mirror, which breaks and reflects it into two tunnels positioned at a right angle to each other (L shape), each 4 km in length. At the end of each tunnel, another mirror reflects the ray back at the first semitransparent mirror. These tunnels are kept in a vacuum, isolating them from any external disturbances. This way, and as long as the structure of reality is stable within the tunnels, the two rays should hit back at the same time, and cancel each other through the refracting mirror, into a final point. But if a distortion in space does occur, like that of the gravitational waves, part of the structure of reality expands while the other shrinks, just like the movement of a snake. And when this happens, the ray of light moving through the expanded space covers a longer distance, especially in comparison to the ray of light that runs through the other part that shrunk. This discrepancy between the two rays would be picked up by the LIGO device sensors. In fact, it was noted on the morning of September 14^th, and after several months of research and verification that followed, the LIGO physicists went public with their astonishing discovery – the last proof needed for Einstein’s theory.

What grabbed the attention of the public most, was the fact that the gravitational waves were identified by measuring light waves. Yet, the way this information travels through space, and our ability to capture it, is more like sound waves in music. It is the song of the universe. Because the change in the structure of the universe happens at such a miniscule scale, at only a fraction of an atom’s proton, it is invisible to the naked eye. But it can be heard as a sound. The scientists translated the results that were observed into sound waves, and this brought forward much data. Because the frequency of the gravitational waves from the black holes’ collision differs from the frequency of their gravitational waves when were still spiraling around each other prior to the collision, the sound that was captured reflects this difference. Prof. Scott Hughes a LIGO employee from MIT, says that “The vocabulary of the [event] is imprinted on the wave”. So, if until today we could only learn about the universe through our eyes, now another sense has come into play.

Time travel and clues of the big bang

Just like Prof. Hughes, all of the scientists involved are extremely excited about this discovery. If we were to phrase it poetically, the universe has been writing its songs for so long, but only now are we able to listen. If you were wondering what they sound like, ironically, the resonance of a gravitational wave resembles the sound of sci-fi movies, a bit like a whistle or a blip in alternating tones. The British composer Arthur Jeffes has created music based on the sounds of the discovered gravitational waves.

But why are scientists so anxious about exposing these ripples in the structure of reality? On top of proving Einstein’s theory of relativity, gravitational waves hold immense significance for developing the knowledge of mankind – it is a new way for us to get to know the universe. Gravitational waves carry with them, across space and time, the story of events happening on such a large scale and at astronomical distances from us, shedding new light on critical phenomena. Quarts magazine outlines some of the possible implications of this new information, and they are dazzling. First, the gravitational waves offer information about the bodies that created them, in this case the original black holes. Secondly, they can teach us about distortions in space and time, and scientists expect that they can also be used for time travel. Additionally, they open a door to finding clues about the big bang.

The discovery of gravitational waves also holds immense significance about the way we perceive reality. The universe is now seen as a creative entity, which constantly sends out information in all directions. Intriguing questions arise about our part in the whole jigsaw puzzle – in what other ways is the universe revealing its truths to us? What will these tell us about the origin of mankind? How has it been made possible that we should even develop a will to understand such secrets? And what is the significance of our perception? We can go on and on, with endless thoughts and questions about gravitational waves and the hidden realms of the cosmos.

But what is truly amazing, is that all of this was triggered by two black holes that merged together – each at a mass of 30 suns – which have now become known to us through a whisper, the softest sound of an infinitesimal difference that is only a fraction of an atom’s proton in size, yet caught by a laser beam.