- #1

rspandher

**[SOLVED] gravitational attractions**

why matter like to attract. does matter repel other matter just as like charges do according to coloumb 's law. how do we know that matter attracts only and does not repel

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- Thread starter rspandher
- Start date

- #1

rspandher

why matter like to attract. does matter repel other matter just as like charges do according to coloumb 's law. how do we know that matter attracts only and does not repel

- #2

dr-dock

i can only say that no one can prove or deny the existance of negative mass. it's out of our experience.we just do not have enough evidence. but if negative mass exists then oposite masses do repel according to gravity law.Originally posted by rspandher

why matter like to attract. does matter repel other matter just as like charges do according to coloumb 's law. how do we know that matter attracts only and does not repel

- #3

pmb

Originally posted by dr-dock

i can only say that no one can prove or deny the existance of negative mass. it's out of our experience.we just do not have enough evidence. but if negative mass exists then oposite masses do repel according to gravity law.

I wouldn't go that far. The best explanation so far for the observed accelerarted expansion of the universe is gravitational repulsion. Einstein's equations allow for it and that's the way it appears to be.

Pmb

- #4

jammieg

after all it seems like nature is all about dichotomy for every negative there seems to be a positive so why not anti-gravity? Why don't the planets repel instead of only attract? I came up with a notion they might possibly explain this a year ago, but it works great in theory just

not so well mathematically.

Check out the topic "a physics expirement with magnets and a vote pole", and give it your guess, the results of the expirement don't really prove anything but may suprise a lot of people. Later,

I'll post what inference might be drawn from this expirement and it has implications on gravity.

- #5

LURCH

Science Advisor

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Originally posted by dr-dock

i can only say that no one can prove or deny the existance of negative mass. it's out of our experience.we just do not have enough evidence.

Not sure I agree, there. Maybe it's just a matter of semantics, though.

Although we currently lack any way of

In the same way, something that behaves in exactly the manner that negative energy is predicted to behave has been observed. To me, this constitutes compelling evidence (if not absolute proof) that negative energy does exist. One of these predicted behaviors is that negative energy is gravitationally repulsive.

- #6

russ_watters

Mentor

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Einstien showed that gravity is a result of massive objects bending space. The 2d analogy is a bowling ball on a trampoline. Put two next to each other and their combined warping of space (the trampoline) makes them attract. This also explains why light is affected even though it has no mass. It follows a straight path over the curved space.

- #7

pmb

Originally posted by russ_watters

Einstien showed that gravity is a result of massive objects bending space. The 2d analogy is a bowling ball on a trampoline. Put two next to each other and their combined warping of space (the trampoline) makes them attract. This also explains why light is affected even though it has no mass. It follows a straight path over the curved space.

That is not what Einstein showed. Einstein did show that gravity **can** curve spacetime. That doesn't mean that gravity **is** curved spacetime. In fact you can have gravity without spacetime curvature. Think of curvature as tidal forces. One does not say "gravity is tidal force" - the reason being is that tidal force is a *difference* in gravitational force. Hope that was clear.

Think of gravity as being of the same nature as a non-inertial frame - is the spacetime is curved the the equivalence is said to be "local" in that you can't transform the gravitational field away in a finite region.

Pmb

- #8

rspandher

- #9

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Place a bowling ball on a sheet and hold the corners tightly, so the sheet is suspended. Then place a tennis ball on the outside and watch it roll towards the bowling ball, or center of the sheet. This is, I think, a good example of how gravity works, the object distorts space-time and causes it to 'bend' and have 'ripples' in it. Now, there is no particle of such that is the agent of gravity, maybe the graviton, but there really isn't a means by which gravity works, on the distortion of space-time.

EDIT: Unless I'm wrong of course

If an object is moving like this:

------>

and there is an object down the way

----------->

O

and the gravitational field of that object is large enough to intersect with the course of the moving object, then the object will fall into its "ripple" and you will observe gravity, like so.

---------------

-------->O------->

EDIT: Unless I'm wrong of course

If an object is moving like this:

------>

and there is an object down the way

----------->

O

and the gravitational field of that object is large enough to intersect with the course of the moving object, then the object will fall into its "ripple" and you will observe gravity, like so.

---------------

-------->O------->

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