Nergis Mavalvala (Professor of Astrophysics, MIT) works on instrument development, precision measurements, and data analysis at LIGO and Advanced LIGO, the gravitational wave interferometer. In 2010 she was named a MacArthur Fellow.
PI: Scientific discoveries often happen where two or more fields intersect. What's your favourite scientific intersection, and why?
NM: In my own work, quantum physics and gravitational physics have a very practical intersection. We all know that gravity is a very weak force – people have waxed poetic about how weak it is – and therefore we know that gravitational effects are small. But how small is small?
Consider a garden variety binary neutron star – every garden should have one! We predict that the presence of such a binary in our galaxy would create a gravitational effect here on Earth. If I was about a metre tall, the effect of having a binary neutron star in our galaxy will change my height by about 1/1,000th of a proton. Now, we're not actually looking at neutron stars in our galaxy; we're looking at neutron stars in nearby galaxies, 1,000 times further away. And we're not looking for their effect on me; we're looking for an effect in an instrument 1,000 times bigger than me. But it works out to about the same thing. We're looking to measure a movement, a change in length, of about 1/1000th the size of a proton .
So what we're doing is looking at purely classical systems, at stars and black holes, but their manifestations here on Earth are so small that they are quantum.
PI: Breakthroughs often happen at the broken places. What's the most exciting broken place for you?
NM: There are several big questions – for me the most interesting ones are dark energy, dark matter. What are these huge effects that are out there that we just don’t know about? We think they are most of the universe, and yet we can say almost nothing positive about them.
Also – this will not surprise you – I am very interested in the question, what does the gravitational universe look like? Why have I spent 20 years working on LIGO? Because it's so exciting, to think that we will soon be able to see the universe in a completely new way. It will be like getting a new sense to go along side our eyesight.
On the subject of things that are hidden – I think there are great discoveries to be made about the early universe. We have learned so much from the cosmic microwave background, which was the first moment when light decoupled from matter, and we could see the universe for the first time. That’s our first signal. But our second signal isn't until much, much later, when stars began to gather into the first galaxies. What happened in between? What was the universe like when the stars first began to shine?
I also think we are just beginning to understand how quantum materials work, and just beginning to truly get a handle on quantum information and quantum computation. I expect that in my lifetime we will see the first fruits of these new understandings – that we will see quantum computers. The road to them has been slow and hard, but I think they are coming.
PI: "I am a physicist because.."
NM: ... Of the process of elimination. Certainly I have a natural aptitude for science and mathematics, and certainly my education has amplified those. I could have been a biologist, or I could have been an engineer, but the first time I had to dissect a cow's eye, I said, "I am OUT of here." And though in my work I take on engineering problems almost every day, I find that what keeps me going isn't the engineering, but the big questions behind it.
That's a better answer. I am a physicist because I like asking big questions about the universe.