The REAL source of Gravity might SURPRISE you...

hey crazies for 250 years we treated gravity as if it was a force like any other that model explained both falling on earth and orbits in space it seemed Universal but about a century ago we learned that model is wrong gravity is actually curvature of space-time and most of the gravity we experience on earth is curvature in time yes time can curve this episode was made possible by generous supporters on patreon to be fair I can understand if you're shocked or confused right now or golf you can probably picture some kind of space curvature it's not a huge stretch but time curvature what does that even mean it's a fair question so let's start with a simple experiment see we've got a tall building like really tall it's poking out into space we're ignoring any engineering difficulties just just go with it on the ground floor there's a photon launcher it sends out a photon every second on the top floor there's a photon timer it receives the photons and measures the time between them if we assume an absolute time frame for everyone and everything in the universe which is certainly what our intuitions tell us to do we'd expect the photon timer to receive a photon every second but that's not what happens the photon timer actually receives a photon every one point zero zero zero zero zero zero zero zero zero zero one seconds yes I know that's a hundredth of a nanosecond difference but it's still a difference that means clocks on the top floor of a building tick just a tiny bit faster than clocks on the ground floor when two independent clocks tick at different rates we call that time dilation I would have called the time variation instead cuz it isn't actually dilating but so be it the point is time passes at different rates in different places for example time passes more slowly the closer you are to the earth the earth causes it that's what time curvature looks like around the earth that's how it's perceived I know right time dilation is real and it matters our GPS network would fail rather quickly if we didn't account for it within a day of turning it on your location would have a seven-mile error but it gets even crazier than that the type of time dilation involved in that building experiment is called gravitational time dilation not because it comes from gravity but because it causes gravity I know that sounds weird but but hear me out just for a minute forget everything you know about gravity imagine it doesn't exist in that imaginary world there's no reason for this world to fall he just floats there that's Newton's laws at play no one balanced force means no acceleration no acceleration means if he wasn't already moving he's not gonna start now next let's say there's time dilation caused by the earth remember time passes at different rates in different places the heights of the clocks don't have to be that different though any difference will do so imagine we attach two clocks to a squirrel one on his head and one on his feet they should tick at different rates - the difference isn't that much in fact it's even smaller than it was for the building it's only an extra for one hundredths of a femtosecond at the head for every whole second - the feet but any difference will do no matter how small unfortunately watching clocks tick doesn't actually give us the right intuition let's try something a little different if we only consider the up-and-down direction that frees up the sideways direction for something else like time for example this is just a space versus time graph nothing too crazy we've been looking at graphs like that for hundreds of years to look for patterns in motion except the squirrel isn't moving remember we're still in that imaginary world with no force of gravity that means we expect this squirrel to be at the same height at all times he has no reason to fall to the ground or does he let's take everything we've learned so far and put it all together the squirrel is hovering above the earth and space but it's moving forward in time I mean everything is moving through time but we also know time flows at different rates in different places you could think of it like a flow gradient around the earth and what happens when there's a gradient stuff gradients are the reason that anything happens ever oh the squirrels head moves faster through time than his feet this gradually turns his motion arrow what we call the four velocity over time it points more and more toward the earth the squirrel falls to the ground simply because time dilation exists surprise we just predicted gravity this whole time we've been imagining a universe without a force of gravity but as long as time passes at different rates in different places things will fall anyway gravity exists even if we don't treat it as a force why does the squirrel fall because there's a flow gradient in time why does the moon orbit the earth because there's a flow gradient in time the weird universe we've been imagining is our universe whoa dude to be clear though it's not time itself that's flowing time doesn't do that and neither does space the flow you're seeing in this animation it's just there to give you intuition I've just replaced the ticking clocks with a bunch of imaginary point particles so wait what about point particles what about it if they feel gravity sure how do they feel that time gradient flow thingy they don't have any size well because calculus while we consider all these elementary particles to be points with no size we don't actually know that's true they're just smaller than we can measure but even if they are points with no size the math doesn't treat them that way if we shrink this world down to subatomic scales the two clocks get closer and closer but they're never at exactly the same place and they're never ticking at exactly the same rate there are always two clocks sometimes they're just infinitesimally close to each other so where does gravity come from it comes from time dilation that's the idea that time passes at different rates in different places large masses like the earth don't exert a force they just make time pass more slowly nearby them this creates a gradient in the flow of time which bends space-time paths gravity is just time curving into space time is more fundamental than gravity so got any questions about gravity please ask in the comments thanks for liking and sharing this video don't forget to subscribe if you'd like to keep up with us and until next time remember it's okay to be a little crazy several of you asked about electron orbits in the last video no electrons do not orbit in orbital is not an orbit it's a visual representation of the probabilistic existence of quantum particles anyway thanks for watching

Channel: The Science Asylum

Views: 1,556,243

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Id: F5PfjsPdBzg

Length: 7min 43sec (463 seconds)

Published: Sat Jun 13 2020