What are gravitational waves?
Gravity, according to Einstein's general theory of relativity, is how mass deforms the shape of space: near any massive body, the fabric of space becomes curved. But this curving does not always stay near the massive body. In particular, Einstein realized that the deformation can propagate throughout the Universe, just as seismic waves propagate in Earth's crust. Unlike seismic waves, however, gravitational waves can travel in empty space — and they do so at the speed of light.
If you could watch a gravitational wave head-on as it moves toward you, you would see it alternately stretching and compressing space, in the up–down and left–right directions.
Is inflation the only thing that can produce gravitational waves?
No. Anything that's massive and is undergoing violent acceleration is supposed to produce them. In practice, the only gravitational waves that we might be able to directly measure would be those from cataclysmic events such as two black holes colliding and fusing into one. Several observatories around the world are trying to pick up the distant noise of such black-hole mergers.
Why couldn't gravitational waves be measured directly, but only detected via a radiotelescope?
The gravitational waves that originated during inflation are still resonating throughout the Universe. But they are probably now too feeble to measure directly. Instead, scientists look for the imprint the waves have left in the broth of elementary particles that pervaded the Universe around 380,000 years after the Big Bang, which we see via the 'cosmic microwave background'. Observations of the microwave background radiation are made using telescopes that detect radio waves, and so the 'ripples' in the background caused by gravitational waves could only be detected by a radiotelescope.
Why was the discovery made at the South Pole?
The Amundsen–Scott South Pole Station, which hosts BICEP2, sits on the Antarctic ice sheet at more than 2,800 metres above sea level, so the atmosphere is thin. The air is also very dry, which is helpful as water vapour blocks microwaves. And Antarctica is also virtually uninhabited, so there is no interference from mobile phones, television broadcasts, and the rest of our electronic paraphernalia.Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot be obtained from elsewhere.
Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.
First Evidence of Gravitational Waves ---
(By LIGO)
(By LIGO)
Scientists announced on previous Thursday (11th Feb) that they have glimpsed the first direct evidence of gravitational waves, ripples in the fabric of space-time that Albert Einstein predicted a century ago.
When two black holes collided some 1.3 billion years ago, the joining of those two great masses sent forth a wobble that hurtled through space and reached Earth on September 14, 2015, when it was picked up by sophisticated instruments of LIGO ( Laser Interferometer Gravitational-wave Observatory).
