Question

How does a force act on an object without the source making any contact with that object?(I am talking about non-contact, action-at-a-distance forces like gravity and electricity)

Answer 1

through fields.

Answer 2

Well that's what I pretty much don't understand. How can fields causes forces?

Answer 3

it causes potential ... and objects move from higher potential to lower potential.

Answer 4

That's a great point. Thanks.

Answer 5

Not really sure ... variables make things too complicated on physics.

Answer 6

I've read that Michael Faraday introduced electric field. That means Coulomb had failed to account for the origin of the electric force! Similarly Newton was unable to explain the origin of his gravitational force. People in coulomb's time must have been amazed to see that a force can be caused without really making contact(it would have seemed like magic!).

You've got a point, but the concept of electric potential can come only after you introduce the concept of an electric field(potential is a property of a field).

Was electric field introduced to explain electric force? Is electric force the result of superposition of fields?

Answer 7

To be honest, i never understood these things. If you are looking for details then it is believed due to interaction or exchange of particles. There are 4 interactions known, they are here
http://en.wikipedia.org/wiki/Fundamental_interaction
Every force <-- mechanical or non mechanical (magnetic) are result of these force.

I seriously don't understand a thing.

Answer 8

sorry about earlier answer ... I had been thinking mathematically. LOL

Answer 9

It says that photons cause the force between electrical forces. How?

Answer 10

when charge is accelerated, then electromagnetic radiations are emitted.

Answer 11

Oh. Even I don't understand these! lol
Particles like these were discovered much after Michael Faraday's work. If Michael had an explanation, why can't we? :P
You're consider the effect before the cause! For the charge to be accelerated, a force must act on it.

Answer 12

ExperimentX, you surely deserve a medal for your work. But due to this new system, I've to wait for others to answer too -_-

Answer 13

I am not after the medals. Seriously, I would love to understand these things.

Answer 14

Right, me too.
If anyone can put Faraday's soul into his/her's, please explain how an electric force can act without contact!

Answer 15

Even I have been curious about it. And honestly, I don't understand this interaction and most of the scientist don't get it either. But there are several theories on it. I think one theory suggests exchange of particles; the quark particles. Like for gravity, there must be a particle called gluon (maybe I'm not sure and the particle accelerators are for finding such particles only, I think not sure again :/ ). Then there is theoretical Higgs-Boson particle, it only exists theoretically. The scientists at CERN are trying to disprove/prove its existence through their Large Hadron Collider. I think the existence of the particle establishes why mass exists or something like that. I am not sure about this, not sure at all, as all this information has been acquired through some random articles and documentaries. So you will need to research a lot on this topic yourself. And also this is a very interesting field to research in, maybe you can research on this someday. Goodluck.

Google is the best tool to search on these topics.

Answer 16

Let us forget modern Physics for a while. Faraday must have accounted this force due to the concept of the electric field that he introduced. How do you think interaction of different fields can produce a force?

Answer 17

Maybe everyone me, you and all particles modify the fabric of space-time around them. I don't think we can visualize this but maybe. Hmm and then due to such modifications of the space-time fabric, forces act on objects.

Answer 18

every electric charged particle develops an electric field around itself where its presence can be felt(exerting a force on any particle which comes into this field) so ur question basically asks how the forces were developed as explained previously by experimentx it is due to this field(represented by electric line of force) that difference IN ELECTRIC potential develops and we know that everything from a water stored at a height falls down due to this potential difference developed(previously in 11th we were like oh the gravity===graviational force is the one behind the flow) but now what causes this force of attraction causing the water to flow from aheight? the potential energy it had also known to us beautifully as the graviational potentail developed at that height(-GMm/r) is the one responsible for thie creation/working/running of this graviational force and other forces

p.s: i am comfortable using the word garvity(just entered 12th nah?) but yes the same happens w electric charges...the only difference here being that the potential energy possesed by the electrons/charged particles is not by virtue of position......

Answer 19

And if you're trying to put yourself in Faraday's position then it may not work. Not everyone knows what they are doing. They just assume stuff and then do it. Maybe. Like Einstein, Bohr before forming their theories both of them assumed or introduced postulates. Like in case of General Relativity Einstein simply assumed nothing can go faster than the light itself, but it may bot be true and same is the case with Bohr's theories. Again, I am not sure like always.

Answer 20

I hope you get my point, the point I am trying to make here. Faraday was a brilliant scientist, my physics teacher told me, he didn't even used to have experiment records; all in the head. But like other brilliant physicists it is highly possible that he didn't knew the complete truth, he simply assumed stuff like others did.

Answer 21

@Jemurray3 @nikvist @JamesJ

Answer 22

arent forces reactionary? repulsion and attractions are forces that need no physical contact. But as far as what the casues of those forces are, i aint got a clue

Answer 23

from what ive come across; all the models try to best explain how forces interact as opposed to what actually creates them.

Gravity effects things, what creates gravity? stuff like that ... in my opinion

Answer 24

it is hypothesized to be graviton <--- a massless chargeless some kind of particle which hasn't been able to detected yet.
But someday I will catch a handful and show everyone "hey buddy this is graviton"

Answer 25

@salini,I think that is an effect of force, not a cause. Yes, I just entered class 12.
@Ishaan94, Yes, you got that right! I was indeed trying to put myself in Faraday's position. Maybe you're right, he might have just assumed that fields superpose to cause force, and proceeded with his experiments. But he was a brilliant experimentalist indeed.
@amistre64, yes forces do not depend on contact. We know that, and take that for granted. That's what I am putting the 'why' after.
It's very non-intuitive that a force can act without contact. You can make someone feel hurt by slapping him, but can you make him feel pain without touching him? Nature shows that electric force can indeed do that(the nature of gravity is still controversial). But why/how?

Answer 26

the last domino falls without the first one ever touching it .... provided youve got more than 2 dominos of course, domini? dominea?

Answer 27

an eqrthquake miles away at see can destroy a harbor town without ever touching it

Answer 28

keys on the keyboard can be typed without ever pressing them too apparently lol

Answer 29

That's because of gravity, a still controversial concept. (Newton said it was a force but couldn't explain it's cause, while Eienstein said it was a result of curvature of space.
An earthquake creates seismic waves, which travel through the earth's crust. It does disturb everything in it's path. It's a contact force.
When we type, aren't our fingers and the keys in contact?
I think an electric field is more than just a space around a charge. Maybe I could imagine it like a spherical halo around a charge. When two halos collide, BAM! A FORCE!

Answer 30

this might provide some insight on electromagnetism
http://en.wikipedia.org/wiki/Maxwell's_equations

Answer 31

@Ishaan94, I've thought of a way Michael could have thought of electric field - philosophically.
Suppose a boy is trying to hit a street dog with a piece of stone. You go immediately and request not to hit the animal. You explain to the little boy that animals are living beings just like us, so they would feel the same pain on being hurt that we would. On saying these things, the boy throws away the stone and walks away.
You stopped the boy without touching him. Rather, you created an 'influence' on him, and that influence did the same thing that would have happened if you had tried to hit the boy - he would've not hurt the dog. So, you created a force without contact, and that can be done only when you can create a field where you can 'influence' other objects.

Answer 32

Yes but the question still is, what makes the object influence or create such a feild to influence other objects. I mean there could have been no interaction at all.

Answer 33

Hello everybody :) I am never around here anymore, so I just now got notified about this conversation. It's a very interesting one, so I'll toss in my two cents for what it's worth.

In the 19th century, when the laws of electricity and magnetism were being formulated, it was discovered that a charged object experiences a force if another charged object is nearby. The force was determined to be proportional to the two charges and inversely proportional to the square of the distance between them, a fact which is now called Coulomb's law. However, the mechanism by which this influence was transmitted was not known at all.

Physicists are generally uncomfortable with the idea of "force-at-a-distance". It is and was, for many reasons, an unappealing concept. Instead, the idea of the electric field was introduced. Field, in this context, should be defined as no more than "a quantity defined at every point in space (except the locations of point charges, but forget that for the moment)". That's it: just a *quantity*. In the case of the electric field, that quantity was a a vector; the force per unit charge that a charged object would feel if placed in that exact spot.

With the definition of the electric field, the mechanism then went like this: 1) A charged object creates this entity called an electric field, that exists at every point in space. 2) That electric field exerts a force on any other charged objects nearby. This eliminated the need for action-at-a-distance by making the field the mediator of the force.

Though I cannot profess to be an expert on modern particle physics, the general idea is that those fields are manifestations of the influences of force-mediating particles, and are not continuous entities (as in the classical picture described above) but, on the quantum scale, discrete and lumpy. It's not like throwing a bowling ball back and forth, though, as such interactions can be attractive as well, but finding an analogous interaction on the macroscopic scale is useless and futile, as such particles to not behave according to our everyday experience.

Finally, I should mention that in reality there is no such THING as a contact force. The reason I'm not falling through the chair on which I am sitting at the moment is because the electrons on the outer surface of my body are being repelled by the electrons on the outer surface of the chair. It is electrostatic forces that TRULY govern what we naively think of as "contact" forces. These forces are all but invisible until the distance between two objects becomes very very tiny because we are neutral ON THE WHOLE but since the electrons live outside their nuclei, on that tiny tiny scale objects seem negatively charged to one another and repel. Once you realize that "why don't charged objects behave like blocks on inclines and baseballs and grapes" doesn't actually make sense because EVERYTHING behaves in this mysterious and esoteric way, accepting Coulomb's law for its minimalist nature may be a little easier to swallow :)

Answer 34

there are many virtual particles called antiparticles like quarks ,positron etc that are responsible for such fields
!!

Answer 35

Anti-matter is a different concept think. Wikipedia says that photons are responsible for electromagnetic fields.

Answer 36

With respect, khanitha, that sentence looks as though you wrote random words related to modern physics on a dartboard, put on a blindfold, and then mentioned the ones that you hit. Antiparticles and virtual particles are not the same thing, quarks and leptons (leptons include the electron and its respective antiparticle, the positron) do not mediate forces, and lastly (this last bit is actually a subtle point) the force carriers, including the photon, are NOT responsible for electromagnetic fields. They REPLACE electromagnetic fields (which are continuous) in the quantum mechanical picture. We still talk about electromagnetic fields because they are infinitely easier to calculate with and still give the right answer on classical scales, much the same way Newton's law of gravity is still applied rather than dragging out the full machinery of general relativity to calculate planetary orbits and whatnot.

Answer 37

just read stephen hawking;'s The theory of everything.,,,it is mentioned there about the field that is created by virtual particles.thats why i mentioned it !!