At the Easter gathering this year there was a trampoline, and while the kids destroyed themselves on it, I stood at the edge with my coffee and watched the best physics demonstration money can buy.

One of the older kids sat down in the middle, making a deep dip in the fabric, and a smaller one rolled a ball from the edge. The ball curved, gracefully, inevitably, spiraling in toward the seated kid, and the small one shrieked with delight and did it again. And again. And I stood there thinking: that is it. That is the actual model, the one Einstein spent eight years finding, being demonstrated at a family lunch by people fully occupied with lamb.

Because here is what Einstein did in 1915, and no matter how many times I read it, the audacity still gets me. Newton had said gravity is a force, an invisible pull reaching across space, and for two centuries that worked beautifully, with one embarrassment nobody discussed: nothing explained how the pull was transmitted. Einstein's answer was that it is not transmitted, because it does not exist. Nothing pulls. Instead, mass bends the geometry it sits in, exactly like the kid dipping the trampoline. And everything else simply moves through that bent geometry in the straightest possible line, which, in a curved place, is a curve. The ball is not attracted to the kid. The ball is going as straight as the fabric allows, and the fabric routes it inward. The moon is not being reeled toward Earth on an invisible cable. The moon travels dead straight through a region that Earth has bent, and dead straight through bent space happens to be a circle around us, forever. John Wheeler compressed the whole theory into one line: "Spacetime tells matter how to move; matter tells spacetime how to curve."

We drove home the next day through the mountains, hairpin after hairpin, and the road did the thing mountain roads now do to me, it turned into the idea. Because notice what the road engineers did. They did not fight the mountain, no one bores a straight tunnel through every ridge. They read the terrain and laid the road along its shape, and the result, the curling, doubling-back, patient road, is not a compromised straight line. It is the correct straight line for that terrain. Every hairpin is honesty about the landscape.

And somewhere around the third hairpin, with the person I love asleep in the passenger seat and the valley going gold below, the year's gentlest thought arrived, and it has stayed.

I have spent a lot of my life confusing force with fate, believing that whatever kept curving my path must be some pull in me, some flaw with a grip. And I have spent real effort, years of it, trying to fly straighter by trying harder, which works exactly as well as a ball scolding itself for spiraling on a trampoline. But if Einstein is right, and the man has not lost yet, then paths are not about pulls. Paths are about terrain. A life that keeps curving the same way is moving through curved country, country shaped by old masses, and the way you change a trajectory is not force. It is geometry. Move the mass, and the road moves itself.

That is, I realize now, what these four years of quiet mornings and notebooks have actually been. Not pushing harder. Regrading the terrain, slowly, one entry at a time, so that the natural path, the lazy path, the path of a ball rolling honestly downhill, curves somewhere better than it used to.

The kids rolled the ball until dark, and it never once missed. Nothing pulls, and everything arrives. Geometry, patient as a grandmother, runs the whole sky.