That summer, my younger brother and I biked a mile from our house to the railroad tracks every day, where we’d built a hidden fort between the boulders and slabs of rock, making a roof out of leafy branches. Only two boys in the neighborhood knew about our secret refuge, and the four of us squeezed into our cramped quarters, chins resting on bent knees, listening for the train whistle. Even with our hands covering our ears, the train grew louder and louder as it approached, clackety-clackety-clackety, the din finally overpowering, and then quieter and quieter as it moved on, heading West from New Jersey, maybe all the way to California. When I learned about the Doppler effect later, I thought of us in our fort, sunlight filtering through the thick canopy of branches above us, the thrilling racket of the rattling train as the sound waxed and then waned. I don’t know what happened to the other two boys, whom I barely recall. My brother has passed on, an early death from cancer, a loss I still haven’t come to terms with. “So how’s it going,” he’d say in our rare conversations on the phone, his focus always on the present, gaze averted from the past. I wish I’d asked him whether he remembered the light-filled moments in our flight from the darkness at home. I’ve been in California now for many years, my memories growing fainter as that summer recedes in the distance. I remember this: copper pennies we left on the tracks, flattened beyond recognition. How they glistened in the sun.