Life’s up and downs may seem as inevitable as gravity, but somehow 2020 feels worse than usual. If gravity were just a little stronger in our own three-dimensional world, the curvature of spacetime would be greater, and matter could more easily collapse in on itself. This arrangement would make stars, galaxies and planets extremely diminutive, compared with the ones in our reality. If gravity were weaker, Earth would be gigantic, and it might be oddly shaped like some asteroids—or a potato. Although we would still have the spacetime curvature noted in Einstein’s general theory of relativity, such curvature would no longer produce gravitational forces.