In Karen Thompson Walker’s debut novel, The Age of Miracles, an 11-year-old girl wakes up one morning to the news that the earth’s rotation is slowing.

Did you always know that Julia, an adolescent girl, would be your narrator?

I did. I always had a sense of her voice. She has an adult perspective on her childhood, and her character grew out of that voice. She’s an observer and the quality that makes her shy and more on the sidelines also gives her interesting access to what’s going on.

It’s stranger for me to imagine having a sibling (I’m an only child) than it is to imagine this change to the planet. Being an only child is part of who Julia is and how she observes her parents. She’s outnumbered by them.

What sparked the idea for “the slowing”?

After the 2004 tsunami in Indonesia, I read that the earthquake was so massive, it affected the rotation of the earth and our days got shorter by a fraction of a second. I always thought of the sun rising and setting as fixed, but after that earthquake, the earth sped up. I started the book as a short story, and originally I also made the earth’s rotation go faster. In the process of turning the idea into a novel, though, I realized that slowing would be even more haunting.

So many of the slowing’s effects feel plausible: the magnetic fields shift, there are solar storms, and people’s reflexes slow with so much exposure to daylight. Did you do a lot of scientific research?

The fabric of this universe is made up out of my head, but I wanted it to feel real. I made things up as I wrote and then filled in the research. Of course we don’t actually know what would happen, but after I was done with a draft, I showed it to an astrophysicist, who pointed out what felt possible and what was too much of a stretch. It was a fascinating experience, to think about art and science, and the ways in which they do and don’t line up.

Julia’s neighbors have very different responses to the unfolding catastrophe, including those who stick to the 24-hour clock and those who don’t.

This was another outgrowth of my desire to make it seem real. People of different ages and backgrounds do have different reactions to the same event. The clock-timers and the real-timers seemed like realistically different perspectives. Julia is aware of all the people in her cul-de-sac, which is very suburban. You know what your neighbors are up to—or you think you do. I knew Julia would be especially aware of who was going off the clock.

Did writing this book affect your optimism or pessimism about the current state of our world?

If I read a scary story in the newspaper, I find I’m haunted by it. This book grew out of my own quickness to fear, but the premise doesn’t reflect pessimism so much as a concern I have about our welfare in general.