Gravity is the warping of spacetime by mass or energy. A mass like the Earth warps spacetime so that the shortest path, the “path of least resistance,” for inertial movement is towards the Earth’s center.
Using instruments like the Hubble Space Telescope, it’s possible to literally see the warping of spacetime by very massive objects like galaxies and huge conglomerations of dark matter. When you’re looking at a very distant object and there’s a large mass along your line of site, it warps spacetime to produce a visual effect known as gravitational lensing. Here’s a schematic diagram showing how it works.
In Annie Hall, young Woody Allen explains to his doctor that he won’t do his homework because the universe is expanding, so what’s the point? His mother exasperatedly tells him, “You’re here in Brooklyn. Brooklyn is not expanding!”
I post this because I’ve been reading Coming Of Age In The Milky Way by Tim Ferris, as good a summary of the state of cosmology between two covers as a person could ask for. Thinking about the horrifying enormousness and ancientness of the universe might have depressed Woody Allen, but it has a paradoxically calming effect on me. Reading books like Ferris’ is my favorite form of meditation.
Life appeared very early in the planet’s history, earlier than you might have naively guessed. But then for billions of years, it existed only as simple single cells floating in the ocean or sitting in cracks in the rocks. Big complex creatures visible to the naked eye didn’t appear until the planet was two-thirds of the way to its present age. The first insects didn’t appear until nine-tenths of the way to the present, and humans didn’t show up until ninety-nine percent of the way.
Our creation stories start with the assumption that we’re the most important thing in the world, the reason for everything else’s being. The story that science tells relegates us to the periphery. Life has mostly been smaller and simpler than us. I think it’s important to recognize that we might very easily wipe ourselves out, and the microbes will barely have noticed we were even here.
The sun was on my mind today anyway, it being so nice and cloudless outside. But days like today also cause me anxiety. I’m a fair-haired sunburn-prone type, and my dad died from skin cancer, a combination of Scandinavian genes and long hours as a young guy on a ladder helping Grandpa paint houses, plus many more hours on boats and beaches with no sunblock. I stick to the shade, wear hats and generally play it very safe, but still, I feel some dread about the amount of radiation I’m getting from the great thermonuclear reactor in the sky.
My dread does have an upside. It’s fueled a lot of fascination. The sun is a bottomless source of interest if you’re a science geek like me. Continue reading →