Science

In Gravitational Waves, A New And Powerful Way To Speak To The Universe

An artist’s impression of gravitational waves generated by binary neutron stars. (R Hurt/Caltech-JPL)
Snapshot
  • On 25 November 1915, Albert Einstein officially published the gravitational field equations of general relativity.

    To mark the day this year, here are excerpts from Swarajya’s interview with astrophysicist Dr Karan Jani, who sheds light on the monumental discovery and possibilities in gravitational wave astronomy and talks about what ails Indian science.

It’s been only a little over two years since the first gravitational wave was detected by the LIGO Scientific Collaboration, in September 2015, validating a prediction made by Albert Einstein’s century-old theory of general relativity. Ever since, there have been five more detections of gravitational waves. Such has been the pace of these detections that they are now starting to be seen as ‘routine’ – the extent of progress in this nascent field of gravitational wave astronomy has been nothing short of remarkable.

What can we expect going forward on this exciting scientific journey? How will India contribute to this frontier area of research? And what ails Indian science? Swarajya seized the opportunity to catch up with Dr Karan Jani, a member of the LIGO Scientific Collaboration and Indian Initiative in Gravitational-wave Observations, to get his thoughts on all these different areas.

Here are excerpts from the interview:

“Then I would have been sorry for the dear Lord,” Einstein famously said when asked how he would have felt if his equations on gravity were proved wrong by astronomical observations made during the total solar eclipse of 1919. Now, almost nearing the centenary of that event, you have made this monumental discovery. What do you think Einstein would have said about it?

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It’s almost impossible to put myself in his shoes. Just the realisation waking up on the morning of 14 September 2015, while looking at the detected gravitational wave signal (and four times such signals since), that we are the first set of beings with consciousness on this planet (and likely in the entire Solar System) to witness such a fundamental phenomenon of the cosmos!

And it’s such a mindbogglingly abstract concept – ripples on the four-dimensional ocean of space-time, within which lies the entire universe. This detected phenomenon to be in agreement (within our experimental precision) to everything Einstein’s theory predicted a century ago is – I don’t know how to express it in any language. It’s a triumph of the abilities of the human brain to sing in the language of mathematics and manifest the ragas of nature.

But this is the discovery to which Einstein would have most notably thanked the spirit of scientific collaboration. Hundred years, thousands of scholarly publications, scientists affiliated to universities from every continent and, most important, consistent funding from government agencies. This is what it takes to uncover the fundamental questions of our existence.

1929: German-Swiss-American physicist and mathematical genius, Albert Einstein (1879-1955). (Keystone/Getty Images) 1929: German-Swiss-American physicist and mathematical genius, Albert Einstein (1879-1955). (Keystone/Getty Images)

What problem does Einsteins theory of general relativity, which forms the basis of your experiment, have with quantum mechanics?

The very notion of “time” is different in these two extreme realms of our universe. Quantum mechanics can describe to us everything from the phenomenon of light to the behaviour of particles of the tiniest sizes to now the digital revolution. Arguably, two-thirds of the global GDP relies directly or indirectly on the applications of quantum physics. But in this quantum realm, time is an arbitrary thing which you could replace with any other yardstick. Once you start digging into this rabbit hole, you will realise that it’s difficult to think of ‘time’ as something “quantum” (discrete). You can break a second into a millisecond, microsecond, nanosecond and so on, but there is no “jump” between the past and future. It appears to be smooth.

In Einstein’s theory of relativity, which explains the universe at the grandest scale, ‘time’ is as much a fundamental building block as the other three dimensions that define ‘space’ around us. We experience this every day with the GPS on our mobile phones. Time slows near the surface of the earth, compared to the satellite which is transmitting the signal. Therefore, we need Einstein’s equations to ensure we reach our destination as per the time measured on our clocks and not the one on satellites guiding us!

But if you keep zooming into an empty spot up to the Planck length (10^(-35) metres), what is considered as ‘space’ and ‘time’ should get fuzzy. So this is where we expect the “smooth” transition between the past and future to break down and be replaced by some form of quantised version of geometry, which is still a work in progress.

As we now have proof for the existence of gravitational waves, are we also going to seek its carrier particles – gravitons? And can we now expect a happy marriage between quantum physics and gravity?

The marriage between quantum physics and gravity should already exist for the cutest object in the universe – black holes. They are heavy enough to impact gravity (space-time geometry) and compact enough that quantum behaviour should have an important say in describing them. We are unable to see the song and dance of this marriage because our experiments have not reached such sensitivity. And, more important, we do not know exactly which beats to expect from their dance as we don’t have a theory of quantum gravity.

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But what we are currently able to do with LIGO observations is put limits on the speed of space-time ripples that are generated during the rapid motion of black holes. If these ripples (or gravitational waves) travel slower than the speed of light, it means gravitons (hypothetical particles that carry gravity) have some mass, and this would be inconsistent with Einstein’s theory of relativity.

Can you tell us about gravitational wave astronomy – how will it change the way we see the universe?

All that we knew about the universe until 2015 – from its age to its largest structure to the birth and death of stars – had been through measuring light (electromagnetic radiation) that was emitted from different parts and times of cosmic history. But ironically, this light also told us that 98 per cent of our universe is “dark” (matter and energy), and currently we don’t have a fundamental theory that can explain why this is the case. However, the space-time fabric connects the entire universe, and the ripples on this fabric (or gravitational waves) have been recording the story since the very instance of the birth of our universe. So, gravitational waves are the most fundamental way in which the universe communicates with us.

After decades of experimental and computational work in gravitational waves, we now have the capability to dissect astrophysical sources with unprecedented detail as, unlike light, these gravitational waves are practically invisible and carry uncorrupted information across the cosmos. With their help, we are now probing the shapes of black holes, the matter inside neutron stars – things that no telescope could possibly ever see. We are already learning how the heavy elements are produced in our universe and whether there is an undetected population, such as the Goldilocks black holes, which forms the basis of my research.

And LIGO is just the first telescope of gravitational wave astronomy, spanning a small part of the spectrum. Within the next two decades, newer detectors would probe the entire gravitational wave spectrum of our universe.

The original 100-year-old documents of Albert Einstein’s prediction of the existence of gravitational waves are put on display at the Albert Einstein Archives of the Hebrew University in Jerusalem, Israel. (Lior Mizrahi/Getty Images) The original 100-year-old documents of Albert Einstein’s prediction of the existence of gravitational waves are put on display at the Albert Einstein Archives of the Hebrew University in Jerusalem, Israel. (Lior Mizrahi/Getty Images)

How will the universe look if there is a being which has evolved organs that can ‘visually’ perceive the universe only through gravitational waves? What kind of a cosmic map would that reveal?

If you think about it, there is absolutely no way nature can produce a biological species that has the ability to sense space-time ripples. These gravitational waves ‘stretch’ every object, living and non-living, in the exact same fashion. So, no matter where you look, your brain simply won’t be able to perceive any difference from a passing gravitational wave. That’s why we built more detectors like LIGO, where we rely on the fact that as the speed of light is constant, we can measure the stretch in distance between two mirrors from these waves. Using this measurement, we are finding events that occurred three billion years ago, and this is generating a map of our cosmos in the gravitational wave spectrum.

How do you see India’s contribution to this field thus far, and where do you see it going in the future?

India has such a rich legacy in the field of gravitational physics. LIGO’s detection proved not only that Einstein was right, but also that Subrahmanyan Chandrasekhar was right on how stars die and more so C V Vishveshwara, through his pioneering work on black holes and their ‘ringdown’. The work carried by Sanjeev Dhurandhar, Bala Iyer, Bangalore Sathyaprakash and their students has played a significant role in shaping gravitational wave astronomy as well as in building a community of researchers in this field in universities and institutes across India.

It is a fitting tribute to this legacy that the current government has sanctioned the building of a third LIGO detector on Indian soil. I do not recall any time in the past when India invested this heavily in a field of science right at its birth. This is particularly motivating for us young scientists, as it guarantees that we will be contributing to next-generation detectors beyond LIGO, such as LISA, which will be the grandest space science mission, and Einstein Telescope.

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A popular introduction to Einstein's universe is the much-acclaimed book by Lincoln Barnett, The Universe and Dr. Einstein, which came as early as 1949 with a foreword by Einstein himself. Since then, throughout the Cold War era, both the US and the USSR produced popular science books so that they would have a science-literate population, which was considered crucial for winning the war. The mantle was taken over by Isaac Asimov, Carl Sagan, Paul Davies, John Gribbin. As a physicist at the core of this monumental discovery, and as an Indian, how do you see the popular science writing landscape in India and its power to take science to our vast population?

It is extremely saddening that the scientific discourse in India is not as prominent as it has to be if we aspire to be a top STEM destination. It is almost a dichotomy as in school we almost single-handedly focus on scoring marks in ‘science’, and then after college, we struggle to name even five Indian female scientists. The two biggest factors responsible, in my opinion, are that the mainstream media, whether it’s the news or TV channels, have not given even a fraction of their time slot to science and innovation stories from the country. And the other is that trained scientists and research institutes couldn’t nurture a platform for science outreach that can be scaled across India. Except in a few cases (like ISRO), rewards from the basic sciences didn’t translate to taxpayers and education policymakers. If one All India Radio episode of Mann ki Baat can inspire students from the smallest villages of India about gravitational waves, then there should be no excuse on the part of us scientists and informed citizens to utilise all social media forums to spread science and scientific temperament. The Department of Science and Technology on its part is also making dedicated efforts towards science communication.

Though India produces the largest number of science and technology graduates, we seem to have a problem when it comes to students pursuing science for research and contributing to it, compared to, say, the Chinese. This is despite the fact that we have a head start and are not burdened like the Chinese, whose country’s official dogma and new physics discoveries can sometimes be at loggerheads. What ails Indian science?

Let me just add that some of India’s top institutes produce research which is at par with the other commonly branded names in the US and Europe. But yes, when we see the overall national statistics, the numbers aren’t representative of the fact that we have consistently funded space programmes for 50 years and have over 3,500 science and engineering colleges. One possible reason (also mentioned in NITI Aayog’s report), is that because of various bifurcations within agencies and ministries, we don’t have a central strategic vision map for long-term investment in the sciences and charting its overlap with education and industry sectors (except for ISRO and DAE, who have had consistent policies and priorities).

State universities and local colleges (where the majority of Indian students enroll) just haven’t been able to capitalise on the available resources at neighbouring research institutes. On top of that, new private universities are being sanctioned at an alarming rate, and it will take them many years to build a credible research milieu. If we don’t come up with a plan now to foster research, at least in government-funded state universities, their existence would be under crisis in a decade or two.

Dr Karan Jani Dr Karan Jani

And what is the way out?

We need an equivalent of demonetisation for our education system. None of the ones either receiving education (students), imparting education (teachers), paying for education (parents) or requiring this education (industries) is satisfied with the current outcome. It’s going to require a tedious policy reform to fix every step of the way from primary to college education, but we have to come up with indigenous solutions and not rely on the Scandinavian or American education model.

For nurturing research and innovation in universities, we should have a consistent framework that sets priorities for spending resources based on the needs of their home state, benefits to local industries and national initiatives (Swachh Bharat, Digital India). The Atal Innovation Mission and Government of Gujarat’s Student Startup and Innovation Policy are some of the promising steps in that direction.

Recently, there has been opposition to the proposed neutrino observatory in Tamil Nadu by groups which, one should say with regret, are not adequately science-literate. What is your view on neutrino research and the role that India can play to further it?

The Indian Neutrino Observatory has such a strong scientific case and potential to make India a part of Nobel prize-winning discoveries in particle physics. Alas, what is happening is a dark chapter and that would be remembered in the history books as a failure of our system. Neutrinos are our link to the next fundamental theory of physics, as they are the only particles whose behaviour does not match with the prediction of the Standard Model. Therefore, it is a field that we have to consistently and ambitiously fund without second thoughts. Neutrinos also play a major role in multi-messenger gravitational wave astronomy.

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Hollywood has been churning out some very good science-fiction films over the years, ranging from Gravity to Interstellar to Arrival. Which ones did you enjoy the most, both as an average moviegoer and as a physicist?

At the cost of losing street value among my peers, I am not the biggest fan of sci-fi films. I prefer drama and animated films and everything made by Guru Dutt. I wish a popular Bollywood actor makes a movie on professor Vishveshwara – “The Black Hole Man of India”. His story is as inspirational as they come and it is one that needs to be told to generations of students.

What about Interstellar in particular? They had Kip Thorne advise them on the film no less, and it showed. Were you impressed?

There is an obvious bias towards Interstellar because of the association with Kip (who was also the PhD adviser of my undergraduate thesis adviser). The film is a case study on how movies can be effectively used to promote abstract ideas of science. That bending of light visual around Gargantua black hole was educating to even folks in astronomy and astrophysics. Few cheesy lines were avoidable, though, like “Love transcends dimensions of time and space.” No, it doesn’t!

Executive producer Kip Thorne attends the premiere of Paramount Pictures’ <i>Interstellar</i> at an IMAX theatre in Hollywood, California. (Kevin Winter/Getty Images) Executive producer Kip Thorne attends the premiere of Paramount Pictures’ Interstellar at an IMAX theatre in Hollywood, California. (Kevin Winter/Getty Images)

Are there any popular science resources you would recommend to our readers who may be interested in keeping up with science regularly? Podcasts, books, magazines – any that you perhaps listen to or read every day?

Twitter! That’s where I find my dose of science beyond the exposure one gets from being in a university and a research centre. Twitter users @AstroKatie, @seanmcarroll, @techreview and @nasa are some that I check every day. For those who wish to understand relativity on a conceptual level, I highly recommend Spacetime Physics by John Wheeler and Gravity by James Hartle.

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