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Wednesday, February 24, 2016

Wow! India too will have a Ligo

So, the “mathematico-physical” prediction of that gifted brain of Einstein, which remained as the figment of imagination for over a century, has at last been proved right: Two black holes,  set about a kilometre away from each other—one containing 36 times as much mass as the Sun and the other 29 times—were locked in an orbital dance. Accelerating rapidly, it brought them closer. Finally, when they met, there was a violent wobble for a minute as quintillions upon quintillions of mass redistributed. And in a jiffy, a larger black hole was formed.  The new black hole is, however, less than the sum of its parts. For, the rest, equivalent to three solar masses, turned into energy. The thus released energy travelled across space as a gravitational wave for 1.3 billon years, the undulations of which were finally picked up on September 14, 2015 by the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) located in Washington and Louisiana in the US. And Lo! The experimental physicists have finally identified the first gravitational wave.

Announcing the detection  of the gravitational wave—“the famous chirp” denoted as GW150914—to the world on February 11, the experimental physicists have finally vouch for Einstein’s general theory of relativity. This announcement by David Reitze, Ligo executive director, is indeed hailed by the physicists as a bigger event than even the detection of Higgs boson in 2012, for it has more profound implications:
  • It provides a direct evidence of the existence of black holes
  • Gravitational waves can be used as new tool to probe the universe
  • Astronomers can now ‘hear’ the phenomena of ripples in space
  • One day we may even be able to listen to the echoes of the Big Bang and eavesdrop on the first 400,000 years of the universe
  • Astronomers can also probe into the cosmic mystery of ‘dark matter’ that remained elusive to the conventional telescopes
For Indians and particularly, for those theoretical physicists who were to limit their association with this historical event to the extent of providing theoretical inputs or data analysis, what is more exciting is that immediately after the announcement of detection of gravitational waves, the government of India has announced its in-principle approval for establishing a gravitational wave detector in India—a clearance that is under examination for almost five years.  And this news is greeted by the world with joy—a rare phenomenon, indeed. The reasons are, of course, not far to seek: the presence of another Ligo of same sensitivity at thousands of kilometres away from the US observatories will only enhance the level of accuracy and ability to detect new gravitational events.

To better appreciate this fact, let us first take a quick look at how Ligo works. It is designed to detect the tiny changes—expansions and contractions of about one thousandth the diameter of a proton—caused by the gravitational wave sent out by a cosmic cataclysm in the galaxy. It is “L” shaped with two four-kilometre arms set at right angles to one another.   There is a tunnel in each arm carrying a laser beam. As the name itself indicates, the Interferometer splits a laser beam in two. Then sends the halves to and fro along the identical paths—the arms set at right angles to one another. Later, when the halves come back to converge at the crux of the arms, they travel in step to the detector. But when a gravitational wave arrives at the interferometer, it alters the space-time—stretches space in one direction and shrinks it in the direction that is at right angle—as a result of which  when the beams recombine and arrive at the detector, they are no longer in step, indicating a signal.

However, lot of care needs to be exercised to make it absolutely certain that what is noticed
is gravitational wave, for even a distant seismic rumblings or the vibrations of passing traffic can distort the observations. Secondly, there being only two functional detectors in the world today, it is not possible to triangulate a signal. Which is why, it is not possible to exactly locate the origin of the gravitational waves. Increased number of Ligos will also increase our ability to detect far away signals too.  As India is strategically situated, when our observatory becomes functional, it simply enhances accuracy of observations—observing the same signal, of course, not quite simultaneously, by centres  located in different geographies ensures certainty of the wave. That is where India’s decision to erect its own Ligo with an investment of Rs. 1200 cr made the world hoot for it.

That aside, the very erecting of the Ligo will alter the landscape of Indian science. For, although critical components such as mirrors and lasers are to be imported from the US, fabrication of ultra-high capacity vacuum system that can handle one million litres of vacuum and manufacturing of secondary optics are to be done in India.   The experience of engineering and assembly of the equipment of such high precision nature is sure to lift Indian industry’s capabilities in precision engineering in several other areas. 

This mega science project will draw more students into gravitational wave physics.  As one scientist observed, this facility will simply “improve chances of doing science in India.” And, I for one fervently hope that the erection of LIGO will give the much needed kick to the Indian Science that is incidentally lying dormant since quite some time.

 Pictures: Courtesy: Google images


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