Look in the night sky and you can see forever—our past, our future. In centuries past, people looked up at the stars at this marsh, and in Munich, and in Mombasa, and in Machu Picchu, awed by the same moon, the same light of the Big Dipper, the same velvet blackness that cradles all.

It’s not yet time, on Valentine’s Day, for the marsh’s muskrats. They pair up around April. Males compete for real estate and mates. Monogamous muskrat couples establish territories that can be around 100 feet in diameter. They rarely leave their grounds. Lower-rung muskrats have to toddle off and find their own less desirable territories. Muskrat love is not always easy.

By Jonathan Shipley I’m writing these lines when it’s -8º outside. I just walked the marsh in the pre-dawn light. It was cold. Quite cold. Bundled up, though, I could make my way on the desolate trails: beneath the empty trees; alongside the frozen ponds; up the hillocks of prairies; down the frozen tumps; through the crystalline landscape towards the car; and back home. And, as I write this (warm now in a sweater, cozy now on the sofa), I think of how cold things can be and how warmth comes...