Okonomiyaki_lover t1_je8hhs1 wrote on March 30, 2023 at 4:23 AM

Reply to comment by tmoore82 in Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science by AutoModerator

Spacetime is just the grid we exist on. Every object can have an x, y, z, and time coordinate to describe its location in the universe. While all mass warps space time, very massive objects produce enough warp to be easily seen.

The earth would fly off in a straight line if the sun disappeared. But the sun warps spacetime so the earth orbits this warped part of spacetime.

Spacetime is everywhere (except maybe inside the event horizon of a black hole). Even where matter is. If you had an x/y plane and put a point on it. That point is not separate from the grid.

tmoore82 t1_jebq2hf wrote on March 30, 2023 at 9:12 PM

>If you had an x/y plane and put a point on it. That point is not separate from the grid.

This is part of what I'm struggling with. I'm a mass. If it's just me and spacetime, I'm warping spacetime... around me?

Okonomiyaki_lover t1_jebszo2 wrote on March 30, 2023 at 9:32 PM

The usual example is like standing on a trampoline or something. You put a dent right under your feet. The further away from you on the trampoline, the flatter the surface becomes. It's pretty much the same but in 3 dimensions instead of 2. You do warp spacetime but you're _very_ small and not very dense so you don't cause any amount of warping that matters.

tmoore82 t1_jeby4dz wrote on March 30, 2023 at 10:06 PM

I think that the translation from 2 to 3 dimensions is what gets me. The trampoline example makes sense. But when I try to go 3D, I can only imagine it like a pool, where I'm displacing something else. But another response said that matter doesn't displace spacetime. And you said that a dot on the grid isn't separate from the grid.

I spacetime more like a magnetic field? Defining contours and routes, as well as permeating things that are in its influence?

Okonomiyaki_lover t1_jec0bbn wrote on March 30, 2023 at 10:21 PM

Spacetime is the trampoline. The universe is the trampoline. All you do is move through it like you would move over a trampoline.