What was the inspiration behind “Crossing the Threshold”? How did entropy and the heat death of the universe come into play? Where did the devil fit into all of that?

I actually encountered an old man climbing over the chain-link fence at 22nd Street Station in San Francisco. The rest is imaginary. Except, of course, for entropy and the heat death of the universe. Those are real, I’m sorry to say. My father really did try to explain difficult physics concepts to me when I was ten or so. Not the heat death of the universe exactly, but I remember a long discussion related to the conservation of energy. As a ten-year-old, I contended that if I put some heat in the freezer, I could destroy it. My father did not agree. It was a long conversation and, as I recall, it did not reach a conclusion that satisfied either of us.

As far as I’m concerned, entropy, the heat death of the universe, and the devil are involved in just about everything. I suppose that’s what comes of being raised Catholic and then becoming a scientist.

As you were writing the story, did anything surprise you?

I think what surprised me most was the sandwiches. Who knew that you could trade a mummified crocodile for sandwiches? My characters knew. And they let me know.

Your work is vast, ranging from short stories and novels to nonfiction works about science and travel essays. What sorts of things from your career in science or your traveling experiences did you bring to this story?

One of the things that’s wonderful about being a fiction writer is that just about everything I’ve done becomes useful in one story or another. For this story, I borrowed info and artifacts from travels in Nepal and Thailand and bits gleaned from a long fascination with archeology and anthropology.

I love this piece because you successfully incorporate so many different concepts and expertly weave them into a short space without losing the reader in things like exposition or too much explanation. Every word feels vital to the story. What is your approach to writing such big concepts (like entropy or the heat death) in short fiction and how do you write them so that your audience will understand them?

 I’m so glad you like the story! I gained my experience in writing about big concepts while writing exhibit labels at the Exploratorium, San Francisco’s hands-on museum of science, art, and human perception. I was a science writer/editor there for a couple of decades. On exhibits, the word count was dictated by the space available on the exhibit and by the visitor’s patience. I had to learn to be brief.

Though I studied science in college, I credit the Exploratorium with my science education. The museum was founded by Frank Oppenheimer, a brilliant physicist who had a talent for explaining science. I was lucky enough to work with him for a number of years. He taught me to ask questions and argue (in the right sort of way). He once explained the gyroscopic effect to me over lunch using butter, a bread plate, and a dinner roll as props. These days, I work with Paul Doherty, another physicist who delights in accessible explanations, collaborating on a science column for The Magazine of Fantasy and Science Fiction.

The bottom line is this: I’m fascinated by science. I love to ask questions and I’m not afraid to keep asking questions until I understand the answers. I’m intrigued and I’m persistent, two traits that are essential to understanding. And once I understand, I want to share what I have figured out.

What’s next for you? What other projects are you working on?

I hesitate to say. When it comes to fiction, whatever I tell you that I’m going to do will probably turn out to be untrue. I’m always working on a number of projects, and I don’t always know which ones will take off. I wish I knew.

On the nonfiction side of things, I’m the activity guru (yes, that is my title) at Mystery Science (mysteryscience.com), an ed-tech startup where we are creating an elementary science curriculum designed to inspire students (and their teachers) to love science. Right now, I’m building chain reaction machines that teach about energy. One of my favorite projects (beloved by teachers and fourth graders) is a robot hand made of paper and string.