New discovery could reveal birth of universe
A century after Einstein predicted their existence, gravitational waves are on the brink of being discovered. Experts are thrilled, but why? What are these waves, and how can they help us?
This afternoon, at a press conference, the physicists behind the LIGO experiment are expected to announce the discovery of gravitational waves. The scientific world is buzzing with excitement; everyone else is scratching their heads. Gravity moves in waves?
To understand, we need to rewind a century to Einstein’s general theory of relativity. Until then, the universe had been seen as a box: space and time were constant, and objects simply moved through them. Einstein disagreed. According to his theory, space and time were not constant: an accelerating object could distort them with its gravity.
Imagine two masses: say, two black holes. They exert a gravitational pull on each other, causing both to accelerate and fall into orbit. Their motion releases energy in the form of gravitational waves: tiny distortions in the fabric of space. As this energy is emitted, the masses get closer, until they collide and merge – releasing more waves.
Almost all gravitational waves are so small we have no instruments able to detect them. Those emitted by the collision of two black holes, however, are big enough. If Einstein’s theory is correct, they can distort light on earth.
This is where the LIGO team come in. They have set up ‘interferometers’: shafts along which mirrors bounce lasers in regular patterns. If these patterns fall out of synch in certain ways, LIGO know that gravitational waves are responsible. That is what people are hoping to hear today.
This may sound impossibly abstract, but a lot is at stake. If the waves have been discovered, then the last major prediction of Einstein’s theory has been fulfilled. They could open up new avenues in our research on black holes. They could even reveal those mysterious first 400,000 years of the universe’s history.
The operative word is ‘could’. After all, the physics of this field are still poorly understood – much comes down to speculation. Yet scientists say that the discovery of gravitational waves will be ‘revolutionary’. Are they getting carried away?
Watch this space
For astronomers, it will be ‘like discovering a new sense’, says science journalist Stuart Clark. Telescopes allow us to see the universe, but there are places light cannot reach (such as black holes). Gravitational waves go everywhere – they will be a boon to research. Their existence will vindicate Einstein, and our modern understanding of space.
Let’s get some perspective, say others. Even once Einstein’s puzzle is complete, the questions keep coming. What are black holes actually made of? Are there other universes? Why does any of this exist? In the face of such uncertainty, it is silly to talk of revolutions. All we know is how little we know.
- If you could travel to the planet Jupiter and back, would you do it – even if you had to spend ten years inside a spaceship?
- What is a better use of our time: studying the universe or human nature?
- You are being sent on a mission to Mars that will last six months. You’re allowed to take ten things with you (apart from food, water and clothes). List your choices, and discuss them with the class.
- Look up the history of astronomy. Draw a timeline, marking the discoveries that you think were the most important.
Some People Say...
“The true sign of intelligence is not knowledge but imagination.”Albert Einstein
What do you think?
Q & A
- If we can never know everything there is to know about outer space, why bother at all?
- The poetic answer: thirst for knowledge is human nature. The practical answer: our studies of the universe have helped us in many aspects of our everyday lives. For example, without an understanding of relativity, we wouldn’t have GPS.
- If the waves have been discovered, then what next?
- Scientists around the world will have a party. They will then press on with developing satellites able to detect waves from space (where they could intercept many more than on earth). With this kind of data, experts hope to learn more about how black holes are formed, how the universe began, and the rate at which it is expanding. In time, such information could help us with long-distance space travel…
- Laser Interferometer Gravitational-wave Observatory. Based in the USA and employing 900 scientists, the project is one of many in the world aiming to confirm the existence of gravitational waves. If LIGO succeeds, it is sure to win the Nobel Prize.
- General theory of relativity
- Einstein’s theory established the capacity of gravity to bend space and time. Published in 1915, it turned him into a celebrity.
- Black holes
- Regions of space with such strong gravitational pulls that nothing – including light – can escape them. They are thought to be formed when massive stars collapse under the force of their own gravity, but they are still poorly understood.
- 400,000 years
- To learn about the early days of the universe, we look for light emitted by very distant galaxies. If we detect a galaxy 10 billion light years away, we effectively ‘see’ it as it was 10 billion years ago. But because no light was emitted for 400,000 years after the Big Bang, this period has remained ‘invisible’ to us. Gravitational waves, however, must have been released back then.