〈 Berger | Dillon 〉

what’s the shape, or “curvature,” of the Universe? our Universe is special— it has a v specific amount of energy allowing it to expand FOREVER as a FLAT Universe. to picture this, imagine shining 2 lasers into space. here, they’ll continue in parallel, never meeting or diverging.

our Universe didn’t have to be this way. it could’ve had a large enough energy density that space itself would collapse in on itself in the Big Crunch. if you shone lasers in this Universe, the light rays would meet before meeting back where they started—just like a sphere.

our Universe could’ve been negatively curved if it had a low enough energy density. this open Universe would look like a 4-D saddle, expanding forever.

in more technical terms, astronomers measure a value called the density Ω. if Ω>1, we’d live in a spherical geometry. if Ω<1, we’d live in a negatively curved, hyperbolic geometry. if Ω=1 (and it VERY nearly does!!), we’d live in a flat universe. And we do. This is home.