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-   -   Significance of Gravitational force (http://www.physicsforums.com/showthread.php?t=651007)

paras02 Nov10-12 02:30 AM

Significance of Gravitational force
 
Hello friends !
I got confused in the point that how can a body exert a gravitational force on other body without coming in its physical contact ? Also please explain its mechanism or significance of gravitational force ?

tiny-tim Nov10-12 10:48 AM

welcome to pf!
 
hello paras02! welcome to pf! :smile:

in newtonian physics: same way an electric charge can exert a force on another charge without contact by a field

in einsteinian physics: there is no force, there is only the "warped" geometry of space-time :wink:

paras02 Nov11-12 03:59 AM

Re: Significance of Gravitational force
 
Sorry I am unable to understand the answer given by you. Kindly clarify the question in more simple words.

ImaLooser Nov11-12 04:02 AM

Re: Significance of Gravitational force
 
Quote:

Quote by paras02 (Post 4154327)
Sorry I am unable to understand the answer given by you. Kindly clarify the question in more simple words.

The simplest answer is "we don't know." We don't know why. What physicists have are equations that enables them/us to predict what matter will do.

paras02 Nov11-12 04:10 AM

Re: Significance of Gravitational force
 
you may be corect but I am still not satisfied

Vanadium 50 Nov11-12 05:14 AM

Re: Significance of Gravitational force
 
OK, so you're not satisfied. Sorry about that.

mfb Nov11-12 09:24 AM

Re: Significance of Gravitational force
 
Physics is not about "why", it describes "how". Sometimes, the level of "how" is so deep that it looks like a reason, but it is just a more fundamental description how.
"Why" is something for philosophy.

grzz Nov11-12 09:42 AM

Re: Significance of Gravitational force
 
Faraday pictured a way how to visualise 'action at a distance' by using the idea of a 'field'.

paras02 Nov15-12 01:29 AM

Re: Significance of Gravitational force
 
sorry ! but science is based on proofs not on facts

harrylin Nov15-12 04:50 AM

Re: Significance of Gravitational force
 
Quote:

Quote by paras02 (Post 4152902)
[..] how can a body exert a gravitational force on other body without coming in its physical contact ? Also please explain its mechanism or significance of gravitational force ?

Quote:

Quote by tiny-tim (Post 4153277)
[..] in newtonian physics: same way an electric charge can exert a force on another charge without contact … by a field

in einsteinian physics: there is no force, there is only the "warped" geometry of space-time :wink:

That is in fact Einsteinian mathematics. Just as in Newtonian physics, in Einsteinian physics the effect is described with a gravitational field. That implies that something physical exists in vacuum that mediates the effect. However, we still don't know much about its "mechanism" (perhaps something for the Quantum forum?).

As this is the classical forum, do you want to know "classical" explanations such as by Newton?

Drakkith Nov15-12 05:02 AM

Re: Significance of Gravitational force
 
Quote:

Quote by paras02 (Post 4160174)
sorry ! but science is based on proofs not on facts

No, the only proofs that exist are mathematical proofs. I like wikipedia's definition of a fact:

A fact (derived from the Latin factum, see below) is something that has really occurred or is actually the case. The usual test for a statement of fact is verifiability, that is whether it can be proven to correspond to experience. Standard reference works are often used to check facts. Scientific facts are verified by repeatable experiments.

Science is based on empirical evidence being gathered and explained using models, which are themselves based on scientific theories. A scientific theory is:

"a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment."[1][2] Scientists create scientific theories from hypotheses that have been corroborated through the scientific method, then gather evidence to test their accuracy. As with all forms of scientific knowledge, scientific theories are inductive in nature and do not make apodictic propositions; instead, they aim for predictive and explanatory force.

For example we explain gravity in classical physics as a force, where the magnitude of the force is based on a mathematical formula. This has been verified as being accurate to a very high degree, and only General Relativity is able to predict things more accurately, which is why it is now considered the modern theory of gravity. The fact that gravity acts at a distance, while surprising to many, is nothing special. ALL forces act through a distance. Nothing ever actually "touches" anything else the way you imagine it when you get down to the very small scale of atoms and molecules. Atoms and molecules themselves are not even solid objects. (In the normal everyday sense of "solid" that most people think of)

ImaLooser Nov15-12 09:52 PM

Re: Significance of Gravitational force
 
Quote:

Quote by paras02 (Post 4160174)
sorry ! but science is based on proofs not on facts

Science is based on facts. Mathematical relations that have been proved under certain assumptions may be used. But scientists can't prove that those assumptions are correct.

So natural science can never really prove anything. It's pragmatic: things are used because they work, or not used because they don't work.

Nstraw Nov16-12 03:24 AM

Quote:

Quote by Drakkith (Post 4160310)
No, the only proofs that exist are mathematical proofs. I like wikipedia's definition of a fact:

A fact (derived from the Latin factum, see below) is something that has really occurred or is actually the case. The usual test for a statement of fact is verifiability, that is whether it can be proven to correspond to experience. Standard reference works are often used to check facts. Scientific facts are verified by repeatable experiments.

Science is based on empirical evidence being gathered and explained using models, which are themselves based on scientific theories. A scientific theory is:

"a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment."[1][2] Scientists create scientific theories from hypotheses that have been corroborated through the scientific method, then gather evidence to test their accuracy. As with all forms of scientific knowledge, scientific theories are inductive in nature and do not make apodictic propositions; instead, they aim for predictive and explanatory force.

For example we explain gravity in classical physics as a force, where the magnitude of the force is based on a mathematical formula. This has been verified as being accurate to a very high degree, and only General Relativity is able to predict things more accurately, which is why it is now considered the modern theory of gravity. The fact that gravity acts at a distance, while surprising to many, is nothing special. ALL forces act through a distance. Nothing ever actually "touches" anything else the way you imagine it when you get down to the very small scale of atoms and molecules. Atoms and molecules themselves are not even solid objects. (In the normal everyday sense of "solid" that most people think of)

i agree

paras02 Nov16-12 09:36 AM

Re: Significance of Gravitational force
 
Thank you guys


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