As a respected high energy physicist, Dr. David Saltzberg’s work has brought him to many remarkable places: Antarctica, his classroom at UCLA, CERN’s Large Hadron Collider, and to the set of CBS’s The Big Bang Theory, for which he is the scientific consultant.
I had the opportunity to speak with Dr. Saltzberg about his experiences and the implications of his work in detecting high energy particles (to quote Dr. Sheldon Cooper, “Bazinga!”).
Nina Sinatra: How did you become interested in astroparticle physics?
David Saltzberg: Since college and probably before, I was drawn towards particle physics and accelerators. They seemed to be the most direct way to find out what matter is really made of. Despite being warned away from joining such large experiments, I found myself as a graduate student at Fermilab, working at what was until recently the world’s highest energy accelerator, for my Ph.D. work. It was a large collaboration, but even in such big scientific groups there is always interesting work to be done and important jobs on the detector that nobody is working on.
Later on, when I came to UCLA as an assistant professor, a major upgrade of the accelerator and detectors became badly delayed. An experimentalist does not like to go so many years without any fresh data. Luckily, Nature provides us with much higher energy beams than we can create on earth, over 10 million times more energy. And Nature’s beams never turn off. My friend and colleague Peter Gorham gave a talk at my university, UCLA, showing how radio waves could be used to detect extremely high energy neutrinos in these natural beams and I was hooked. Our first attempt used ground based antennas, the “Deep Space Network” we pointed at the Moon, looking for neutrinos hitting the lunar regolith. Later this idea changed into flying the antennas and looking down at the Antarctic Ice. That is the basis of our balloon payload, called ANITA: The Antarctic Impulsive Transient Antenna.
N.S.: Tell us a bit about your work on the ANITA experiment — how do you and your colleagues interact with and use neutrino telescopes?
D.S.: The problem with detecting ultra high energy neutrinos is they are so rare, about one hits the Earth per square kilometer per century. So you need to have enormous detectors, hundreds of cubic kilometers, which is bigger than anything you can buy. We use Antarctic ice because it is nearly transparent to radio waves. If a neutrino interacts in the ice, it makes a shower of charged particles that produces a short, sub-nanosecond radio burst. Our payload has 40 antennas observing the ice, looking for these brief radio bursts.
We were very fortunate that NASA’s Columbia Scientific Ballooning Facility exists. It is a wonderful program that allows astronomers to fly scientific payloads at 120,000 feet. Their Long-Duration Balloon program in Antarctica has allowed us flights in excess of 30 days. It is a wonderful confluence of effects that allows the experiment to work: First, the circumpolar vortex set up in the Austral Summer allows us to fly balloons in a large circle around the 80th South parallel. Second, about three-quarters of the world’s fresh ice is there, which is radio transparent. Third, Antarctica is the most radio-quiet continent on Earth. Fourth, the Sun is always up in the Austral Summer so our solar panels can power our instruments 24/7.
N.S.: What is it like to work in Antarctica?
D.S.: Antarctica is the coldest, driest, windiest and on-average highest place on Earth. For the most part our work is conducted in comfortable, heated laboratories built by the National Science Foundation and NASA. Just the trip to and fro each day can be a bit uncomfortable in old Navy personnel vehicles that slowly roll over some bumpy terrain. The nice part about working down there is nobody can call you — so you get real work done.
One activity down there did get us out into the deep-field of the continent. We needed to place a test pulser in the deep ice of the continent to make a known signal for our payload as it floats by. With one of my graduate students, a technician from Hawaii and a mountaineer (provided so the physicists would not kill themselves), we flew out on a ski-plane to a remote site with tents, stoves, pulsers and oscilloscopes. We spent a week “on the ice” deploying our pulser. It made us feel more like glaciologists and geologists than particle physicists.
N.S.: What do you feel is the most exciting implication that your work may have?
D.S.: Since Galileo, astronomers have used telescopes to probe the sky. First just with visible light, but, eventually, with all bands of electromagnetic radiation. But most light is not penetrating and mostly one can only observe just the surfaces of dense astrophysical objects. Neutrinos are extremely penetrating and we can use them to see into the core of such objects. For example, the core of the Sun has been observed using neutrinos, proving the nuclear furnace inside operates as predicted. Along the way, these measurements told us something new and surprising about the fundamental physics governing neutrinos, for example that they have a mass. But besides the Sun and a supernova back in 1987, no other astrophysical object has been seen with neutrinos. Nevertheless, they are surely out there. We just need to build big enough and clever enough telescopes to see them.
N.S.: Many MIT students are big fans of The Big Bang Theory — how did you begin working as the show’s scientific consultant?
D.S.: My friend who introduced me to particle astrophysics was at play here as well. He used to live in Los Angeles and happened to be contacted by a friend of a friend about the pilot script. Since he had since moved away, he suggested that I might be able to help out. So like finding most jobs, this was the old fashioned way: a friend of a friend of a friend. The writers know all about geek lore such as comic books and movies. They even know a great deal of science. But they wanted a consultant around to get it exactly right. They know what nitpickers we scientists can be about science in our fiction.
I started by being shown a script for the “pilot” episode; like an engineering prototype for a show. I made a few small comments and filled out the whiteboards. On the second pilot attempt the show was “picked up” by CBS and the show became extremely successful. I didn’t know what to expect, but looking back, the show is put together by such talented and experienced professionals, that must play a big part in how much fun the show is and how well it was received.
N.S.: What types of advice do you give the writers and actors of the show? Can you remember any especially funny moments while you were consulting?
D.S.: The writers are big fans of science and put quite a lot in on their own. So sometimes all I have to do is look over what they’ve written and check it out. Other times, they will leave a little “[science to come]” and I make suggestions to fill it in. I like to put in modern physics, things that are happening right now, so people can Google it to find out what it is. I put some scientific Easter-eggs on the white boards each week. Viewers who want to know more can check out my blog where I write a bit more in depth about the science in each episode (http://thebigblogtheory.wordpress.com).
Two of the actors, Johnny Galecki (Leonard) and Jim Parsons (Sheldon) visited UCLA once, before the show was even on the air yet. They met a few of our graduate students and postdocs who showed them around the labs and had lunch. But week-to-week the actors do their own research and very rarely ask me a question. Once Jim found a mistake that I missed in the script (“electrical dipoles” rather than “electric dipoles”), so maybe he knows a lot more physics than he lets on.
A funny thing happened at the end of last season. The character Leonard was drunk and drops a beer bottle down the elevator shaft. One of the executive producers, Bill Prady, thought the sound of the crash was too soon. So he ran up to me and frantically asked, “quick, how long does it take for an object to fall four stories?” Now 300 audience members and 100 of the crew are all waiting so I only had a few seconds to make the calculation. He was right and we told the sound engineer how long to wait. So now I can tell my physics students I really DID have to use s=1/2 g t^2 in my life.
N.S.: What are your upcoming research plans?
D.S.: I am currently speaking to you from CERN, the home of the Large Hadron Collider in Switzerland. This is now the highest energy accelerator in the world and a great place for an experimental particle physicist to be right now. Nearly every particle physics discovery made in the previous decades has been achieved by detecting particles called muons. So I am here working on the muon detectors of an experiment called the “Compact Muon Solenoid.” It is called “compact” because it is over 20 meters long. And “muon” is its middle name.