Hello everyone and welcome to the Mindscape Podcast. I'm your host, Sean Carroll.

One of the interesting things about science is that people within science, the working

scientists, can get really quite emotional and tied up in their favorite ideas, even if

we don't yet know which ideas are right, even if we're convinced that eventually the experiments

are going to have the last word and they're going to tell us which ideas are right. Along

the way, we get very attached. We care about one idea being right or the other one, which

is very different than the stereotype of the cold and analytical science type. Part of

that is of course that the interesting part of being a theoretical physicist, the kind

of scientist that I am, is proposing new ideas for what the fundamental laws of nature

might be. A lot of theoretical physics is taking the known laws of nature and working out

what their consequences are. So how do stars form? How do you make a high-temperature

superconductor? How does DNA split and things like that? But another part of it is proposing

entirely better, newer, novel ideas for what the fundamental laws are supposed to be.

And when it comes to that, how in the world are we supposed to know? How to best invent

new laws? Or if someone proposes some new laws? How in the world are we supposed to say,

yeah, that seems plausible to me or no, no, no, that's completely crazy. This is a judgment

call. This is something people who are completely working in good faith will have different

ideas about. So today's guest is Lee Small and probably needs no introduction, very well

known to any of you who are interested in theoretical physics. Lee is one of the pioneers of

loop quantum gravity. He is one of the founding members of the perimeter institute for theoretical

physics in Waterloo, Canada. And one of the interesting things about Lee is that not only

is he working in quantum gravity and related fields, but he thinks very carefully about how

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