How Much Heat Can One Man Handle?

Heat. You know it when you feel it—touching a stove, baking in the sun, inadvertently scalding yourself in the shower. Heat is a burning global issue as well—melting glaciers, raging wildfires, hotter summers.

But what exactly is it? Biologist Bill Streever decided that the best way to find out would be to experience its extremes. National Geographic's Rachel Hartigan Shea spoke with Streever about his new book, Heat: Adventures in the World's Fiery Places.

Your previous book was about cold. Beyond the obvious temperature differences, how do cold and heat differ?

Cold is nothing more than the absence of heat. Cold has a limited range before you bottom out at absolute zero [-459.7ºF, or -273.17ºC]. We can't go very far down, we can't get any colder. But anyone can go 400 degrees up in the oven, and there are places much hotter than that in the Earth. That makes heat a much richer topic.

You subjected your body to a lot of heat.

Some of that's intentional for the drama. Part of the reason I write books is that it lets me do things I wouldn't normally do. I went firewalking, went lava-walking, visited people in houses that had just burned down.

What was it like walking over burning embers?

I felt very comfortable going into the firewalk. I knew that I couldn't get burned unless an ember stuck to my feet. The walk is five or seven paces. It's pretty quick across the fire pit, but there's a totally unexpected feeling of exhilaration. I did it five times, but on the fifth time I got embers between my toes so I stopped.

Is there one experience that will really stay with you?

I spent time at the Brookhaven National Laboratory collider and went into the tunnel where they do high-energy experiments. Humans have achieved amazing temperatures that occurred at the very birth of the universe. To me, it was sort of a magical experience to be that close to something so incredible. I'll be out skiing and I'll think about being in that tunnel.