Convergence Profile: David “Doddy” Marsh

Doddy Marsh (Postdoctoral Fellow, Perimeter Institute) completed his PhD at the University of Oxford.


PI: Scientific discoveries often happen where two or more fields intersect. What is your favourite scientific intersection, and why?
DM: I work at the intersection between cosmology and fundamental physics. The biggest clues we have about physics beyond the standard model come from cosmology: the dominance of matter over anti-matter, the existence of dark matter, the small (but non-zero) value of the cosmological constant, the initial conditions of the universe. All these things are likely resolved by physics on small length scales, but all our evidence comes from physics on huge length scales. 
PI: Breakthroughs often happen at the broken places. What's the most exciting broken place for you?
DM: Dark matter, because it is a tractable problem with a real possibility for discovery. Some problems of physics, like quantum gravity, are tied to energy levels or time scales inaccessible to experiment. But dark matter is out there, and we know the energy scales in which we have to live . We see quite clear evidence for where it is – and where it isn't – and it's a problem that can be solved. That's exciting.
PI: What keeps you up at night, or gets you to work in the morning?
DM: The silliest little problems, not the big questions of physics. I don't lie awake worrying about whether we'll solve dark matter. What keeps me awake is muddling over some integral or change in variables – something that, in the morning, I'll just get down on paper and solve. That’s what brings me to work – knowing that, when I get there, I'll get into a problem, write a draft of a paper, and accomplish something. Also, the free coffee gets me to work in the morning.
PI: How do you recharge your batteries?
DM: Skateboarding! I use skateboarding as a way to wipe the blackboard clean. It is not a scientific activity – there aren't any rules or rigid structures like there are in physics. You can just go out and do it. You need quite a clear head to do physics, and skateboarding allows me to go out and clear my head. It's the way that physics and skateboarding are so different that allows them to fit together.
PI: "I am a physicist because..."
DM: ... I get to be my own boss! I get to chase interesting questions, be imaginative, and be playful with ideas. You do have to be rigourous, and it's not easy, but there’s also a lot of creativity involved. I love telling stories with data.