Setting up a Ligo facility in India presents monumental engineering challenges for the country

It’s been a year now since scientists at Caltech and MIT’s Laser Interferometer Gravitational-Wave Observatory (Ligo) detected the first “chirp” of the aftermath of the collision of two black-holes and confirmed yet another aspect of Einstein’s Theory of Relativity.

That chirp cost over a billion dollars to detect and involved decades of work from some of the most brilliant minds of this century. Over 1,000 scientists from over 16 countries participated in the effort.

Following the news, a number of countries, including India and China, announced their intention of setting up Ligo facilities on their own soil. Whatever the motivation behind the announcements, it must be noted that setting up a such a facility requires a massive investment in terms of money, manpower and brains.

To detect the gravitational waves, scientists had to set up two identical facilities as far apart as they could be set up. These locations also had to be isolated and free from vibration.

Caltech and MIT’s Ligo labs were set up in Washington and Louisiana, separated by around 3,000 km.

The facilities themselves essentially consist of two, 4 km long arms that are set perpendicular to each other. These arms have to be as straight as is humanly possible to make them. The chambers enclosed by these arms need to be in absolute vacuum.

In fact, the vacuum chamber in these Ligo facilities is the second largest in the world, after that at the Large Hadron Collider (LHC). It took engineers 40 days to pump out the air required to create the chamber in each Ligo facility.

When designing Ligo, scientists even had to account for the curvature of the earth. Owing to the curvature of the Earth, one end of a 4 km arm might be as much as 4 feet lower than the other.

Inside these perfectly straight, vacuum chambers is a laser beam. This beam is split into two and sent down each arm. A complicated apparatus consisting of the smoothest mirrors in the world suspended by silica threads that are twice the thickness of a human hair helps with the detection.

The theory is that when a gravitational wave passes through the Earth, it will change the length of the arms. This change in length must be detected by Ligo. However, this change in length is tiny, about 1/10000th the width of a proton. And that’s a proton we’re talking about. Not an atom. A proton in a hydrogen atom takes up 0.0000000000004 percent of the space.

As Jefferson Lab explains, if a hydrogen atom were the size of the Earth, the proton at it’s centre would be 200 meters in diameter. That’s how small it is.

The laser itself is something special. The current Ligo laser is a 1MW laser (that’s enough power for thousands of homes) that is refined to produce just one wavelength of light (very hard to do).

The system so set up is so sensitive that the vibrations of someone braking head on a road hundreds of meters away is detected by the facility. All such vibrations need to be accounted for and eliminated.

Clearly, setting up a Ligo facility in India is no walk in the park. But why bother?

Speaking to The Times of India, Prof Archana Pai, one of the nine principal investigators for Ligo, explained that, “Detection of gravitational waves will help prove many theories relating to space and time, unravel the mysteries of the evolution of universe, stars and galaxies with more precision in future, yet that requires more sensitive detectors.”

Setting up a Ligo facility in India will be very expensive and very challenging, but it should help bolster India’s growing scientific community , and that in itself might be worth the asking price.