A Wave Of Discovery

Making sense of the most important scientific discovery of the century — gravitational waves exist — via FAQs

Updated on: 2 March 2016 2:33 pm

A Wave Of Discovery

On Thursday February 11, scientists in Washington DC, United States, announced that they finally had proof that gravitational waves existed in the universe. This is the most important scientific discovery of this century and proves a 100 year old prediction by the famous scientist Albert Einstein.

What did Einstein predict?

Einstein said that when two black holes? collided or dashed into each other, the energy that was released rippled out in waves of gravitational energy. Gravity as you may know is the force that pulls us down to Earth. It's the reason that things like your ball fall down instead of floating away. Black holes have a terrific amount of gravity and that energy escapes out in waves when two of these holes bang into each other.

Imagine what happens when two heavy objects in a swimming pool dash into each other. Waves would spread out in all directions from that point. Gravitational waves are created in the same way. The interesting thing is that this collision happened more than one billion years ago, and the waves have been travelling through the universe since then until their presence was picked up. It has taken so long for them to travel to Earth because the collision happened very, very far away.

What did they hear?

The gravitational waves were 'heard' not seen. The scientists who made this discovery the scientists listened for 20 thousandths of a second as the two giant black holes, one 35 times the mass of the sun, the other slightly smaller, circled around each other before colliding. On September 14, 2015, they finally heard the sounds-not a big bang but a faint 'chirp' that appeared on the computer screen as a squiggle (mark).

How did they hear something so tiny, and from so far away?

That is a 43 year old story.

In 1972, a scientist in the United States named Rainer Weiss started thinking about building an instrument that would be able to hear these gravitational waves. Although Einstein had predicted them more than 50 years before, no one was quite sure if the waves actually existed as there was no proof.

So, in 1990, after years of planning, the National Science Foundation of the US finally agreed to spend $272 million to build a very high technology machine that would basically be the 'best ear in the world.' Called the Laser Interferometer Gravitational-Wave Observatory or LIGO, it doesn't actually look a human ear, but it is so powerful that it can hear the minutest (smallest) sounds in the universe -- for example, it can hear vibrations that are less than a trillionth of an inch. It took years to make the most sensitive instrument in the history of research 'deaf' to anything other than a gravitational wave.

LIGO started 'listening' for the waves in 2001. After nine years, in 2010 the instrument was shut down for five years as scientists worked to improve it even more. By Sunday, September 13th 2015, all but one test was done and LIGO was left to listen once more. In a few hours, the first wave was heard. Gravitational waves had been talked about for so long but never been proven, that the LIGO team spent months running checks to make sure that they had indeed heard a gravitational wave and nothing else. The announcement was finally made on February 11, 2016.

Why is this discovery so important?

The presence of gravitational waves proves beyond doubt that black holes exist in space. It is also a whole new way of seeing. As Prof Alberto Vecchio of the University of Birmingham (United Kingdom), one of team members at LIGO, said, "We have observed the universe through light so far. But we can only see part of what happens in the universe. Gravitational waves carry completely different information about phenomena (events and objects) in the universe. So we have opened a new way of listening to a broadcasting channel which will allow us to discover phenomena we have never seen before." What we are seeing is the start of a whole new branch of astronomy (the science of studying stars and the universe) called Gravitational Astronomy.

How will we use this knowledge?

Think back to some of Einstein's other ideas such as time dilation, according to which, time passes more slowly at higher altitudes. At the time he made the discovery, no one knew how to use this information. But now without this knowledge we wouldn't be able to operate GPS satellites that are used for finding out the exact location of a person or thing on Earth. In the same way, scientists do not have any direct uses for gravitational waves-at least not ones that you and I will encounter in daily life. However, they are quite sure that they will be able to use them to find out more about black holes and the extraordinary amount of energy they contain as well as measure how fast the universe is expanding (growing).?

What is a black hole?
Black holes are the strangest objects in the universe. It is an area of space where matter seems to have collapsed and folded up. As a result, the matter has been compacted into a very small area that exerts a tremendous amount of gravity. This gravity helps the black hole 'eat' planets, suns and other objects in space around it. The pull of a black hole is so strong that nothing, not even light can escape it. Stars like our sun turn into black holes, when their gravity becomes so strong and the star collapses into itself.

Anita Mani is the founder-editor of Child Friendly News, a fortnightly newspaper that presents news and current affairs for children under 14 (www.childfriendlynews.com). Her interest areas revolve around nature and science, and living as we do in an age of discovery, it is a interest that keeps her quite busy.