Is Gravity acting upwards or downwards?

[Redbeard The Pink]

This may be totally wrong and just confuse things further, but I'm throwing it out there anyway. Someone smarter than me can correct me if I'm wrong.

An object's gravitational field is less a function of matter and more a function of space-time. Objects with mass warp space-time just by being in it.

This "slants" ALL of space-time toward the object in such a way that other objects will be inclined to "roll" toward it. If all objects in the Universe suddenly lost their motion and momentum, they would immediately start rolling toward each other until everything kind of crashed in on itself somewhere in the middle.

There's an experiment on YouTube I saw a science class doing where they stretch out a piece of lycra and place various round objects on it to see the patterns they make as they roll. With the right combination of weights and objects, they could create complex orbit patterns where two marbles (for instance) would orbit each other closely while simultaneously orbiting a much larger object. It's a pretty cool demonstration of the principle I'm describing. Basically, gravity isn't exactly pushing or pulling one way or another. It's more like we're resting on a table where EVERY object on the table tilts the whole table in toward itself. Only we're not resting, we're hurtling outward at high speeds.

I have to stress that this is my limited, layman's understanding of how this happens. It probably makes no sense to anyone but me.

[Alex K]

This may be totally wrong and just confuse things further, but I'm throwing it out there anyway. Someone smarter than me can correct me if I'm wrong.

An object's gravitational field is less a function of matter and more a function of space-time. Objects with mass warp space-time just by being in it.

I'm not claiming to be smarter than you. I just had some classes on relativity

According to the Einstein field equation, the presence of mass and energy of an object warps the spacetime. So in a sense both is true, it is a function of matter, and it warps the space-time

This "slants" ALL of space-time toward the object in such a way that other objects will be inclined to "roll" toward it.

You could say that, yes

If all objects in the Universe suddenly lost their motion and momentum, they would immediately start rolling toward each other until everything kind of crashed in on itself somewhere in the middle.

Now, the cosmological expansion of the universe which I think you are alluding to, is (according to its description via general relativity) not so much the movement of objects through space (they could be at rest, even), but the rescaling of space itself between the objects (the shrinking of all measuring rods, if you will).

There's an experiment on YouTube I saw a science class doing where they stretch out a piece of lycra and place various round objects on it to see the patterns they make as they roll. With the right combination of weights and objects, they could create complex orbit patterns where two marbles (for instance) would orbit each other closely while simultaneously orbiting a much larger object. It's a pretty cool demonstration of the principle I'm describing. Basically, gravity isn't exactly pushing or pulling one way or another. It's more like we're resting on a table where EVERY object on the table tilts the whole table in toward itself. Only we're not resting, we're hurtling outward at high speeds.

You probably mean something like that, no?


It's a pretty demonstration, and a little bit analogous to spacetime, but not really - the demo itself needs gravity to act downwards, so it's not really a demonstration of how the warping of spacetime generates gravity, but circular and therefore a very incomplete one at best: This type of demo can't really work because it has no way of showing the warping of time, but only space, and the warping of time and spice (*) jointly into each other is the essential effect which gives you gravitational acceleration (getting movement over time from gravity is due to space and time mixing, if that makes sense).

Here is a relatively (pun intended) accurate illustration of how gravitational acceleration is generated from space-time-curvature

https://www.youtube.com/watch?v=DdC0QN6f3G4

I have to stress that this is my limited, layman's understanding of how this happens. It probably makes no sense to anyone but me.

(*) unintended Dune joke

[Redbeard The Pink]

Yeah, that's the one. It makes a good visual demonstration, but you're absolutely right about it being an incomplete model. I just like how neatly it demonstrates the general idea of gravitational fields.

[IATIA]

Actually, if one considers the gravitational pull of the cannon ball and the bullet, the cannon ball must fall faster, albeit a negligible difference in that experiment.

Although not if you drop them next to each other, at the same time from the same height

Vectors.    I think there should still be a difference, albeit even more negligible.  Even if only 10E-1000, it is still different.

[IATIA]

---

This may be totally wrong and just confuse things further, but I'm throwing it out there anyway. Someone smarter than me can correct me if I'm wrong.

An object's gravitational field is less a function of matter and more a function of space-time. Objects with mass warp space-time just by being in it.

This "slants" ALL of space-time toward the object in such a way that other objects will be inclined to "roll" toward it. If all objects in the Universe suddenly lost their motion and momentum, they would immediately start rolling toward each other until everything kind of crashed in on itself somewhere in the middle.

There's an experiment on YouTube I saw a science class doing where they stretch out a piece of lycra and place various round objects on it to see the patterns they make as they roll. With the right combination of weights and objects, they could create complex orbit patterns where two marbles (for instance) would orbit each other closely while simultaneously orbiting a much larger object. It's a pretty cool demonstration of the principle I'm describing. Basically, gravity isn't exactly pushing or pulling one way or another. It's more like we're resting on a table where EVERY object on the table tilts the whole table in toward itself. Only we're not resting, we're hurtling outward at high speeds.

I have to stress that this is my limited, layman's understanding of how this happens. It probably makes no sense to anyone but me.

---

I always found the rubber sheet thing very confusing. Basically, the 'warping' of space-time by matter cannot really be displayed as such. I thought that maybe it could be shown better with a three-dimensional Euclidian grid then just pick a point and pull everything to it. I have tried on a couple of occasions to do that in a 3-D modeling program, but I am not very good at 3-D modeling. All I have is Bryce 3D.

Back to gravity. In reality, if something is in freefall, it is stationary with respect to space-time and that is the natural state of anything. All other forces disrupt this natural state. In effect, we are hurtling outward from the earth at 32ft/s/s with respect to space-time.

And to the OP, IMHO, we are being pushed toward the earth rather than pulled toward the earth. Just like a vacuum, you do not get sucked into space, you get pushed.

[Jenny A]

Just a second, let me clarify everything for you with my superior physics:

Bla bla geodesics bla bla bla spacetime bla

Can I have your babies? 

No, I don't really want anymore babies, and you have one of your own to diaper and I sure don't want to diaper any new ones. 

But you make me laugh like no one else here.

[Thumpalumpacus]

I don't really understand how you came to the conclusion you came to.

A push is an action in which the body causing the pushing moves the object it is pushing away from it.
A pull is an action in which the body causing the pulling moves the object toward it.

Neither of those definitions has anything to do with acceleration, or with anything but the object causing the action and the object being acted on.  That is, the comparison itself of how object A interacts with the earth to how object B interacts with the earth, tells us nothing about the nature of the force being applied to it.  Only the description of the interaction between object A and the earth tells us the nature of the force being applied to object A from the Earth.

Wait, are you saying that physical relationships are relative?

Perish the thought!

[Pyrrho]

---

This may be totally wrong and just confuse things further, but I'm throwing it out there anyway. Someone smarter than me can correct me if I'm wrong.

An object's gravitational field is less a function of matter and more a function of space-time. Objects with mass warp space-time just by being in it.

This "slants" ALL of space-time toward the object in such a way that other objects will be inclined to "roll" toward it. If all objects in the Universe suddenly lost their motion and momentum, they would immediately start rolling toward each other until everything kind of crashed in on itself somewhere in the middle.

There's an experiment on YouTube I saw a science class doing where they stretch out a piece of lycra and place various round objects on it to see the patterns they make as they roll. With the right combination of weights and objects, they could create complex orbit patterns where two marbles (for instance) would orbit each other closely while simultaneously orbiting a much larger object. It's a pretty cool demonstration of the principle I'm describing. Basically, gravity isn't exactly pushing or pulling one way or another. It's more like we're resting on a table where EVERY object on the table tilts the whole table in toward itself. Only we're not resting, we're hurtling outward at high speeds.

I have to stress that this is my limited, layman's understanding of how this happens. It probably makes no sense to anyone but me.

---

I always found the rubber sheet thing very confusing.  Basically,  the 'warping' of space-time by matter cannot really be displayed as such.  I thought that maybe it could be shown better with a three-dimensional Euclidian grid then just pick a point and pull everything to it.  I have tried on a couple of occasions to do that in a 3-D modeling program, but I am not very good at 3-D modeling.  All I have is Bryce 3D.

Back to gravity.  In reality, if something is in freefall, it is stationary with respect to space-time and that is the natural state of anything.  All other forces disrupt this natural state.  In effect, we are hurtling outward from the earth at 32ft/s/s with respect to space-time.

And to the OP, IMHO, we are being pushed toward the earth rather than pulled toward the earth.  Just like a vacuum, you do not get sucked into space, you get pushed.

You only get pushed into the vacuum of space if you are in an atmosphere.  It is the atmosphere that pushes you, not the empty space.

[ErGingerbreadMandude]

Just a second, let me clarify everything for you with my superior physics:

Bla bla geodesics bla bla bla spacetime bla

Can I have your babies? 

No, I don't really want anymore babies, and you have one of your own to diaper and I sure don't want to diaper any new ones. 

But you make me laugh like no one else here.

Go Alex,Go Alex,  

He is witty,
he is gritty,
and he is from,
lord knows what city,
let me give you some news,
he got all the right physics,
so fucking smart he's
solving physics at night times.

[ErGingerbreadMandude]

---

This may be totally wrong and just confuse things further, but I'm throwing it out there anyway. Someone smarter than me can correct me if I'm wrong.

An object's gravitational field is less a function of matter and more a function of space-time. Objects with mass warp space-time just by being in it.

This "slants" ALL of space-time toward the object in such a way that other objects will be inclined to "roll" toward it. If all objects in the Universe suddenly lost their motion and momentum, they would immediately start rolling toward each other until everything kind of crashed in on itself somewhere in the middle.

There's an experiment on YouTube I saw a science class doing where they stretch out a piece of lycra and place various round objects on it to see the patterns they make as they roll. With the right combination of weights and objects, they could create complex orbit patterns where two marbles (for instance) would orbit each other closely while simultaneously orbiting a much larger object. It's a pretty cool demonstration of the principle I'm describing. Basically, gravity isn't exactly pushing or pulling one way or another. It's more like we're resting on a table where EVERY object on the table tilts the whole table in toward itself. Only we're not resting, we're hurtling outward at high speeds.

I have to stress that this is my limited, layman's understanding of how this happens. It probably makes no sense to anyone but me.

---

I always found the rubber sheet thing very confusing.  Basically,  the 'warping' of space-time by matter cannot really be displayed as such.  I thought that maybe it could be shown better with a three-dimensional Euclidian grid then just pick a point and pull everything to it.  I have tried on a couple of occasions to do that in a 3-D modeling program, but I am not very good at 3-D modeling.  All I have is Bryce 3D.

Back to gravity.  In reality, if something is in freefall, it is stationary with respect to space-time and that is the natural state of anything.  All other forces disrupt this natural state.  In effect, we are hurtling outward from the earth at 32ft/s/s with respect to space-time.

And to the OP, IMHO, we are being pushed toward the earth rather than pulled toward the earth.  Just like a vacuum, you do not get sucked into space, you get pushed.

You're probably going to find me disturbingly stupid when you find out that i was saying that we weren't being pushed of pulled towards the earth but away from the earth.
Yup,i said that we were being pushed away from earth.

I thought like that only because i visualized gravity as a streched rubber sheet,when i put two objects on top of it the heavier object would come down faster than the lighter object.According to that scenario,if two objects were to be pushed on to the rubber sheet and then released the rubber sheet would push the lighter object faster than the heavier object,so i figured if gravity might've been pulling or pushing stuff toward the earth lighter objects would fall faster than heavier objects but that's not the case so i thought maybe gravity is pushing stuff away from the earth,like a rubber sheet,Argh,i don't even know anymore.I'm going to college and listen to stuff i already know so that i can feel smarter again,goddammit.