The Fabric of Space-time
Image: What happens to light as it passes through a point of space-time in where mass has been applied, as well as why objects in space orbit the way they do (planets, galaxies, clusters, etc.)
Also known as the Space-time Continuum, I’ve always been fascinated about the very space that holds the planet we live on, stars we see at night, solar system we observe, and supernovas we stargaze on telescopes. In astronomy you hear the term space-time get used a lot and I thought I’d highlight key features that describe what this fabric is. I find it odd that not that many people stop to think what holds us up, how are we suspended in space-time? Well, technically we’re not suspended. We’re constantly moving, constantly orbiting. And it’s not just Earth and the solar system joining in on this cosmic dance, you can include star clusters, galaxies, super clusters and even Blackholes, just about everything in our Universe. Keep in mind that even as you read this post, our solar system is orbiting the Milky Way galaxy, traveling at roughly 220 kilometers a second!
What is Space-time?
Einstein visualized gravity as a manifestation of the curvature of space-time - the three space dimensions and a fourth time dimension. Most of us cannot visualize a curvature of four dimensional space-time, so visualize a curved two dimensional rubber sheet. Placing a mass on the rubber sheet curves it downward like space-time curves in the presence of a mass. On such a rubber sheet a small mass can circle around the curvature produced by a large mass, just as planets orbit the Sun. Or a mass can roll straight downward just as an object falls to the Earth. Space-time being the very “material” these events and masses take place on.
Einstein explained gravity as a result of the curvature of space-time near the presence of a mass. The differences between general relativity and Newton’s law of gravity only become noticeable when the gravitational force is very strong.
Einstein’s general theory of relativity is one of the crowning intellectual achievements of the 20th century and led to such predictions as black holes, gravitational lenses, and the expanding universe. So far it has passed every experimental test with flying colors.
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