Lan Todak

Matter creates gravity

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Not just mass, energy also.

Matter and energy bend spacetime, and in spacetime, objects take the shortest path in spacetime, which because of the its curvature move in curved trajectories. We experience this as gravity.

When you are new to this topic, this article might be a good introduction.

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Moderator Note

Moved to relativity

 

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3 hours ago, Lan Todak said:

How?

As Eise says, mass/energy bends space, and that is what we perceive as gravity. We don't know why mass/energy does this. We know that it does, and have a well-supported theory on what happens as a result.

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2 minutes ago, Lan Todak said:

I know... but empty space is alive

Not by the definition used in science. What do YOU mean by "alive"?

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3 hours ago, Lan Todak said:

I know... but empty space is alive

?

Gravity is spacetime geometry.

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10 hours ago, Phi for All said:

Not by the definition used in science. What do YOU mean by "alive"?

I mean empty space has unique properties and account to  97% total energy of our universe. matter can not simply bend empty space. 99.9999999% energy of a matter resides in empty space too.     

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OK let's clarify something here. First consider the following definitions.

Mass is resistance to inertia change

Energy the ability to perform work.

Spacetime a geometric model system with 3 spatial dimensions with 1 time dimension.  In physics dimension is an independent variable or value that can change without affecting any other mathematical object.

So how does mass curve spacetime. Well GR models bodies in free fall that is without any force applied. Time is given units of length and can be called an interval. This is done by setting c which is constant to all observers and adding a unit of time. So the time coordinate is given units of length by ct.

[latex] (t,x,y,z)=(ct,x,y,z)=(x^1,x^2x^3x,x^4)[/latex] the last is in four momentum form for convenience as its useful to model a particle trajectory along the x axis.

Now what is spacetime curvature. Well space is just volume... (Very important ) it isn't a stretchable bendable fabric...

Those are just analogy descriptive. 

What spacetime truly means by curvature is the worldline paths for light it us the null geodesic. 

If you shoot two laser beams in flat spacetime those beams stay parallel. If spacetime is curved then the beams converge for positive curvature and spread apart for negative curvature.

 This is a consequence of how the mass term affects the time it takes for a particle to go from emitter to observer. That whole resistance to inertia. 

So let's drop two objects toward a planet. You have the usual Centre of mass. As the objects free fall they do not stay parallel. They will converge upon one another as they approach the center of mass.

That what is really meant by curvature the free fall paths are curved. Not the volume of space.

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15 hours ago, Mordred said:

OK let's clarify something here. First consider the following definitions.

Mass is resistance to inertia change

Energy the ability to perform work.

Spacetime a geometric model system with 3 spatial dimensions with 1 time dimension.  In physics dimension is an independent variable or value that can change without affecting any other mathematical object.

So how does mass curve spacetime. Well GR models bodies in free fall that is without any force applied. Time is given units of length and can be called an interval. This is done by setting c which is constant to all observers and adding a unit of time. So the time coordinate is given units of length by ct.

(t,x,y,z)=(ct,x,y,z)=(x1,x2x3x,x4) the last is in four momentum form for convenience as its useful to model a particle trajectory along the x axis.

Now what is spacetime curvature. Well space is just volume... (Very important ) it isn't a stretchable bendable fabric...

Those are just analogy descriptive. 

What spacetime truly means by curvature is the worldline paths for light it us the null geodesic. 

If you shoot two laser beams in flat spacetime those beams stay parallel. If spacetime is curved then the beams converge for positive curvature and spread apart for negative curvature.

 This is a consequence of how the mass term affects the time it takes for a particle to go from emitter to observer. That whole resistance to inertia. 

So let's drop two objects toward a planet. You have the usual Centre of mass. As the objects free fall they do not stay parallel. They will converge upon one another as they approach the center of mass.

That what is really meant by curvature the free fall paths are curved. Not the volume of space.

Do you mean in 4 dimensional space?... in 3d, space distorted whenever object passing by like when black hole is passing over galaxy. At least we can clearly see distortion in 3d. A mass can really curve space... i am just asking how... in quantum level.   

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Posted (edited)

In QFT treatment through the principle of least action. You can work through the Eueler Langrene equations that correlate the kinetic energy of the particle to the chosen path probability with the fields potential energy. Feymann has a good starting beginner's lecture.

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.feynmanlectures.caltech.edu/II_19.html&ved=2ahUKEwj7pa__0_bjAhXpiVQKHZgNBJAQFjABegQIDhAG&usg=AOvVaw1AQkf2xpc5d5gpPkpVjEqu

The definitions above apply in all physics treatments so set them to memory.

Though mass may be replaced by coupling constants in different field treatments.

The SM models 18 parameters are all various coupling constants. 10 are Yukawa couplings 2 are the Higgs. I'd have to double check the others 

Edited by Mordred

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