The final scene in the movie Gravity has always stuck with me. It’s beautiful: after 90 minutes of nail-biting space hullabaloo, viewers watch Sandra Bullock’s character swim out from the underwater wreckage of a spacecraft and gratifyingly tread up to the surface. It’s a long-awaited denouement, the moment when she finally reaches home. When her head rises from the water, you can hear mosquitoes and see the outlines of mountains in the distance. Her gargantuan breaths feel like a chorus of voices proclaiming the magnificence of earth and everything in it.