eli5 How does gravity work? Where does it come from?


eli5 How does gravity work? Where does it come from?

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as far as we understand now, it’s just a fundamental property of the universe. It doesn’t come from anywhere else, it just is. If you can find out what causes gravity to exist, cone collect your nobel prize.

More specifically, what’s fundamental is that mass warps spacetime. Gravity isn’t a *force* so much as the natural consequence of objects moving in curved space. No one has any answer why mass curves spacetime beyond “it juat does”.

Basic model of gravity was explained to me when I was a kid with a towel and basically any item.

Stretch out a towel and hold it by its corners until it’s almost even. Then drop something heavy-ish onto the towel.

The towel is no longer even and there’s a ring around the item that “drags down” the towel. That is a representation of gravity. Put another item next to the first item on the towel. If the items are close enough, the heavier item might pull the lighter item into its indent. Thats a basic model of how gravity interacts between two objects.

Gravity is the curvature of spacetime caused by mass. Think of it like a person sitting in the middle of a trampoline.

There are 4 fundamental forces in nature: weak nuclear force, strong nuclear force, electromagnetic force and gravity.

Physicist still don’t exactly know where gravity comes from. All we know, it’s that it’s the weakest of all four.

According to Einstein, gravity is a distortion space time around heavy objects which is why it attracts other bodies (think of it like a bowing ball on a trampoline and how it bends it)

But where exactly this force comes from, as far as I know, is still a mystery.

We don’t know. All we really have are mathematical models that predict the behavior of gravity to a degree well enough for all current applications. Current theories describe mass to curve spacetime, but we have no idea why that happens.



this video always stuck with me

We don’t exactly know where it comes from.

We know it works at large scales by warping space and time.

We can predict how it works at large scales using Einstein’s equations, but that doesn’t mean that these equations explain how gravity works on its most fundamental level, what causes it or how it is related to fields, elementary particles and so on.

My explanation is a bad, but alternative explanation than the common theory. 🙂

I did once rad a theory about time and gravity being two direction of the same thing. Meaning, if you think of time as driving toward the east and gravity as driving north. Meaning, if you move faster in time do you have less gravity and if you are heavy do you move slower trough time. This should be called gravitational time.

It explains it a bit like if you start to turn around yourself with your arm out to the sides, and you turn faster and faster will your arms feel like they get pulled away from you (centrifugal force) the same should be happening with time vs gravity.

Space time exists like a giant trampoline. Everything is on it.

Heavy things warp it, like a bowling ball sitting in the middle.

this causes other things to roll towards it. that’s gravity, the fact things get pulled in and heavier/closer = more pull etc

so gravity is just observing that dip in the trampoline and its effect.

[There is a theory](https://en.wikipedia.org/wiki/Entropic_gravity) that or universe is actually 2D, it just looks 3D, and that the 2D waves somehow decay or spread out which in the 3D version looks like stuff clumps together.

That theory is probably just sci-fi, though. The real answer is nobody knows – it just is.

People keep saying, “We don’t know where gravity comes from,” but we totally do. If you adhere to Newtonian physics, then sure, there’s no explanation for the source of gravity. But Relativity makes it clear that Newtonian physics is merely a fairly good explanation of how gravity behaves, not an accurate explanation of what it IS.

So in short, gravity is not a force. It’s not even a *thing.* Gravity is a *shape.* We human beings think of shapes as three dimensional, but actual shapes are four-dimensional because they exist in spacetime, not just in space. When we ask where gravity “comes from,” it’s like pointing at a circle and asking, “Where does *roundness* come from?” The fact that gravity seems to *act* is due to the fact that every object in the universe is in motion through spacetime. So what seems stationary to us, because the Earth is our frame of reference instead of an inertial frame of reference, are really just other things following the same path through spacetime as we are. What we perceive as the action of gravity is really our inertia following the curvature of the spacetime around us.

It’s very hard to let go of the idea that everything around us is stationary and that we’re moving through time, but that’s what prevents us from experiencing gravity for what it actually is. We evolved to perceive it as something completely different from reality.