Why do things attract or repulse?

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Offline J Rahman

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Why do things attract or repulse?
« on: 07/09/2009 07:05:29 »
Force, as I see from a child's point of view, is merely a pull or push. Hence, it seems that if I need to pull or push a body, I must get hold of it. I mean to say that if I want to pull a body, I first must grab it and then give it a pull, or if want to push a body I must have to strike it with some object (say, my hand). But in any case, I cannot exert a force on a body unless I touch it.

But, as seen in most of the natural forces such as forces of electricity, magnetism and gravitation, a body exerts a force on another body without feeling the need of getting into touch, quite similar to how magicians do.

How does nature manage to do such a great trick? I think my question is about the root cause behind the forces of nature. Newton says that mass is the factor responsible for his gravitational force. But what is the great deal there? I see, as I said earlier, any mass does not seem to exert a force unless it touches the other mass. But in reality, such conditions do not apply, but why? I just want to get a simple explanation.

Magnetism, on the other hand, shows some fuzzy phenomena that confuses me more than I need. If I suppose that there is some invisible factor responsible for the natural forces, then the factor must be true for all cases ie. it should be impartial so as to produce an effect in each and every particles of the universe. I don't understand why magnets are partial to magnetic particles only.

Probably, you all might find various misconceptions in this post and it is possible for I'm merely a high school student. Please clarify my conceptions and let this force-problem be resloved.
J Rahman,
Highschool Student,
Assam, India.
Ph. +91 95779 44185
(Visit my blog here and also find me on Facebook)


Offline graham.d

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Why do things attract or repulse?
« Reply #1 on: 07/09/2009 12:52:52 »
To be truthful the nature of forces is not fully understood. Maths and physics can predict effects, but it is hard to say that this corresponds to true understanding. What you regard as simple "touching" is also exerting a force at a distance too, even though the distance may be very small in this case. This is because matter is not "solid" at an atomic and/or subatomic level and there are more forces at work than the gravitational or electromagnetic ones you mention.

In general the problem, as with many modern physics issues, is that the world in much more complex than our brains have been structured to cope with. There are no survival imperatives that would mean our brain has to cope with a world of more than 3 dimensions or speeds beyond that which we would experience in everyday life. There would have been no value in knowing that at sub-atomic levels the rules we can deduce of how large objects behave will no longer work. Understanding such things, in any deep sense, is only really judgeable by how well your intuition can predict behaviour. There are few that would claim to be proficient at such an activity and the maths can be quite hard to fathom too.

There are different ways to look at forces too. A quantum physicist may wish to consider a force as an exchange of particles where a electromagnetics expert may wish to consider force as a "field" or a cosmologist as merely a curvature of 4 dimensional space-time. Nobody has really been able to unify these different conceptual views of (different) forces in one workable theory yet, though there are some contenders.

This maybe a glimpse of the sort of problems in understanding forces in any deep and consistent way but I hope will stimulate your interest, even if not satisfying your curiosity. I expect many here would be happy here to answer more specific questions, as would I, but your very general questions are quite hard to address.


Offline lightarrow

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Why do things attract or repulse?
« Reply #2 on: 07/09/2009 12:57:59 »
We are more prone to believe in forces as being generated by contact between bodies, because this is our past sensorial experience; if we had been trained with magnets when we were little, we wouldn't think in this way.

Contact between bodies is not actually a simpler description; think what *actually* means "contact": atoms interact at some (very little) distance through electromagnetic forces... there is no "contact".

Edit: graham.d has beated me so my answer is quite a subset of his...
« Last Edit: 07/09/2009 13:02:35 by lightarrow »