3. What are gravitational waves? Why are scientists trying to detect gravitational waves? Discuss. (15 Marks)
गुरुत्वाकर्षण तरंगें क्या हैं? वैज्ञानिक गुरुत्वाकर्षण तरंगों का पता लगाने की कोशिश क्यों कर रहे हैं? चर्चा करें।
Candidates need to explain gravitational waves and discuss why are scientists trying to detect them.
Albert Einstein suggested in 1916, that gravitational waves could be a natural outcome of his general theory of relativity, which says that very massive objects distort the fabric of time and space—an effect we perceive as gravity. But it wasn’t until 2015 that the LIGO team directly detected gravitational waves, using a pair of ultra-sensitive detectors. The discovery ended a century of speculation and confirmed Einstein’s original prediction. Accordingly, very massive objects spiralling toward each other should wrinkle space-time and send those distortions across the cosmos, like ripples spreading across a pond at the speed of light.
What are gravitational waves?
- Gravitational waves are ripples in the otherwise tough, stiff fabric of spacetime produced by the most violent phenomena the cosmos can offer—things like exploding stars and collisions between ultra-dense neutron stars or merging black holes.
- In essence, gravitational waves “are propagating disturbances of the shape of spacetime.
- Gravitational waves are washing over Earth all the time, but instruments have not been sensitive enough to detect them until very recently.
Why are scientists trying to detect gravitational waves?
- Since LIGO’s first detection of the gravitational waves, we’ve gained unexpected insight into the cosmos. That’s because gravitational waves are a new way of “seeing” what happens in space: We can now detect events that would otherwise leave little to no observable light, like black hole collisions.
- With the detection, astronomers were able to combine gravitational waves with more traditional ways of seeing the universe, helping to untangle mysteries about the dense, dead objects known as neutron stars.
- LIGO has opened a new ‘window’ on the universe. Things like colliding black holes are utterly invisible to EM astronomers. To LIGO, such events are beacons in the vast cosmic sea.
- More importantly, since gravitational waves interact very weakly with matter (unlike EM radiation, which can be absorbed, reflected, refracted, or bent), they travel through the Universe virtually unimpeded, giving us a clear view of the gravitational-wave Universe. The waves carry information about their origins that is free of the distortions or alterations suffered by EM radiation as it traverses intergalactic space.
- The gravitational waves that LIGO detects are caused by some of the most energetic events in the Universe—colliding black holes, merging neutron stars, exploding stars, and possibly even the birth of the Universe itself.
- Detecting and analysing the information carried by gravitational waves is allowing us to observe the Universe in a way never before possible, providing astronomers and other scientists with their first glimpses of literally un-seeable wonders.
- LIGO has removed a veil of mystery on the Universe and in so doing, has ushered in exciting new research in physics, astronomy, and astrophysics.
The first detection of gravitational waves was a very important event in science. Before this, just about everything we knew about the universe came from studying waves of light. Now we have a new way to learn about the universe—by studying waves of gravity. Gravitational waves will help us learn many new things about our universe. We may also learn more about gravity itself.