Madeline is in the swing, her face the picture of delight. “Mo, mo,” she cries and kicks her legs to show me that she wants me to push her higher and faster. I push, and push, and push with both hands. There is no thought in my head except for her joy. I’m completely present in this moment. It’s perfection. Madeline embodies the eternal now and she carries me with her, pulling me out of my worries and fears and plans.

But not forever: After a few minutes, my mind and eyes wander. I take in the whole busy playground, crowded with toddlers plunging headlong into adventure and their attendant adults shouting exhortations to be careful, offering snacks, or lost in the tiny offices they carry in their hands. It’s a gorgeous day. Sunny and blue and not too hot, a hint of fall in the breeze. And then my eye is caught by a much younger mom across the playground trying to convince her toddler that it’s time to go.

When Madeline graduates from high school, I will be 57. Jeez, I think, that mom will still be younger than I am now when her kid walks across that stage. If I live to be 85, Madeline will be 46 and maybe by then I’ll have some grandkids. In fact, I’m suddenly convinced of it. Between Madeline and her three-year-old brother Seamus and their 8-year-old sister Rosena, I will definitely live to see grandkids. I reassure myself for the millionth time that having kids in my late 30s was totally fine.

And then another thought comes to mind, the sort of thought that haunts the parents of this moment: When I’m 85, it will be 2059, and what will that look like? When my grandkids are my age now, it could be almost a new century. And what will our planet look like then? And I feel that little chill that must be increasingly commonplace among other parents of 2015.

And then I’m gone. You wouldn’t know it to look at me. After all, I’m still pushing the swing, still cooing and chatting with my buoyant 18-month-old daughter, but my mind is racing, my heart is pounding. This playground will not be here. This tranquil, stable, forever place wasn’t built to last 100 years, not on a planet like this one at this moment anyway.

I look around and I know. None of this—the municipal complex, the school across the street, the supermarket up the road—is built for 100 years, especially not this hundred years. It won’t last. And I can’t imagine a better future version of this either. What comes to mind instead are apocalyptic images, cheesy ones cribbed from The Walking Dead, that zombie series on AMC; The Day After, a 1980s made-for-TV dramatization of a nuclear attack on the United States; Cormac McCarthy’s haunting novel The Road; Brad Pitt’s grim but ultimately hopeful World War Z; and The Water Knife, a novel set in the western United States in an almost waterless near future.

They all rush into my head and bump up against the grainy black-and-white documentary footage of Hiroshima in 1945 that I saw way too young and will never forget. This place, this playground, empty, rusted, submerged in water, burned beyond recognition, covered in vines, overrun by trees. Empty. Gone.