“Physics is always a gamble”

It would be most helpful to String Theory to get a clue from nature that we are going in the right direction, says Nobel laureate David Gross
String theorist and particle physicist Professor David Gross, from Kavli Institute for Theoretical Physics, Santa Barbara, was in India recently to participate in Strings 2015, an annual conference on String Theory, at Bengaluru. He was awarded the Nobel Prize in Physics, along with Frank Wilczek and David Politzer, in 2004, for the discovery of asymptotic freedom, which opened out the field of Quantum chromodynamics. He is also the chairperson of the advisory board of International Centre for Theoretical Sciences, Bengaluru (ICTS). Prof. Gross spoke to Shubashree Desikan about String Theory and the absurdity(ridiculous,बेतुकापन) of retiring at 60. Excerpts:

You have been a keen observer of politics and science in the world, especially India.

I have been coming to India for around 20 years. Ten years back, India was beginning to emerge from a period of stagnation. Talking to people in the government or high up, it was clear that there was a desire to invest in education, and research in science and technology. But my colleagues here, save a few, were very pessimistic. Since then, I have been involved in helping Spenta Wadia [Director, ICTS] and his colleagues develop the ICTS here, which is a marvellous project. One of the motivations to establish the ICTS is to have an institute that brings together physicists, astronomers, cosmologists, mathematicians, biologists all under one roof, talking and helping solve questions posed by nature. I always felt India has enormous(many,बहुत) potential. Here, there is a 5,000-year-old culture with great respect for mathematics and science and, for the last century or two, a great tradition of scientific institutes.

India has mainly been a home for theory…

Theory is cheap. India has had a great tradition of excellence in mathematics and theoretical physics. Tradition and culture, and role models, are important. Experimental sciences are much more expensive, and require bigger investments. But they are absolutely necessary.

Is it possible to continue pursuing just theory and neglect experiments?

No, it’s not healthy… to some extent the world is so open that it is possible to get by for a while by borrowing innovations made elsewhere, but this must, and will, change. But this requires commitment, investment of significant resources and also having the self-confidence that one can compete at the world level. There’s absolutely no reason why you [in India] shouldn’t have that confidence.

You have been observing the changes in procedures for faculty appointments in India. Would you comment on that?

Yes, because I chair the international advisory board of the ICTS. One of the things I have observed that is most destructive and silly is the government’s policy towards early retirement. People are forced to retire here at the age of 60 [65 in some institutes]. That might have been sensible in the 1950s when people lived till 60 (laughs). But now people live till 90. It’s an incredible waste of resources. India is not a country that has a wide, deep pool of talented people, especially people who can be scientific leaders; there is an enormous shortage.

I am 74 and have no intention of retiring. Nobody wants me to retire; in fact, it’s just the opposite. It is extremely difficult to find people in their 60s, which is the optimal age at which people can assume scientific leadership.

I also feel that India is violating a fundamental human right. Age discrimination(favoritism,भेदभाव) is as discriminatory as judging people by their religion, colour, race or gender. Some people at 60 have been sleeping since they were 20. Some people will go on being productive into their 90s.

What are the challenges facing String Theory?

There are many. Most useful would be to find some clue from nature as to whether we are going in the right direction. Some experimental hint as to what the right direction is would be a big help. We have these big experiments at the LHC [Large Hadron Collider]. They have discovered the Higgs particle, which is a big deal. We are waiting for them to discover other particles. They have just started to run again a few weeks ago. We are all very excited. If they discover some of the things that we have been expecting, that would be the most exciting thing. Or, if they discover something else, something unexpected, it will be even more exciting. Whatever they discover will be of interest, because it will tell us what nature is.

Is the LHC finding evidence for physics beyond the standard model?

We think that they are close to such discoveries, but so far [there is] no definitive evidence. Theorists know that there definitely has to be physics beyond the Standard Model, but the right experimental evidence has not shown up yet. But the LHC has covered less than 10 per cent of its capability. The next few years will cover the rest of it. So, it is a very exciting time.

Physics is always a gamble; it is a game of exploration. That’s the fun of it. We never know for sure what will happen. Sometimes, we theorists can anticipate, but nature is the final judge.

What gives you the energy to work in physics?

It’s fun! If I didn’t have the stamina to go on, at some point, I wouldn’t. One of my main goals in life is not to be bored. That is why physics is so attractive to me. Wonderful questions, wonderful mysteries, and often we find the answer to how nature works. Like Asymptotic Freedom and theory of the nuclear force.

When I was a student, nobody understood anything about nuclear forces. So to have the luck and experience of being able to solve that problem, and then, over the next few decades, to see the theory work is amazing. It’s hard to explain to people who don’t have a mathematical background how beautiful it is. You have both the hope and joy of discovery sometimes — that happens rarely — but there is a greater joy. You can appreciate through not just your work but the work of others, the beauty of nature. What could be better? I am a very lucky man.