Superluminal Tennis Balls

[BPHgravity]

Lets say I make a conduit that is the length that light takes to travel in a minute. I then stuff it full of tennis balls so there are no gaps and all the balls are touching each other.

 

I then push on the first ball. Instantaneously, the end ball falls out of the conduit. Is this not faster than light motion?

 

I understand that each ball only moves the length of one ball, but all balls move together at the same time. Lets say someone is on the end of the conduit and waiting for you to perform the action. You shine a light towards the observer, but the ball would fall out before the light gets to their eye?

 

I am sure this is not the first time you have seen or heard this question, so I imagine there some sort of theory or mechanical explanation that is evading my thought process on this idea.

 

[JaKiri]

Barring any actual physical (as in of physics) disagreement, I'd comment with a materials science based one;

 

All structures compress.

 

The time delay from them compressing would be more than enough for the light to travel.

 

No matter how rigid the structure, there is always some give.

 

ps. More physicsy explanations later!

[blike]

I posted a similar question once which involved a long stick that would take light a few seconds to transverse. If we shook the stick at one end, wouldn't the other end move instantaneously?

 

I would assume that the speed at which the energy travels through the balls has a limit at C, and hence the last ball would never fall out before the light reached you. It might seem wierd to think of it like that, because the motion seems instantaneous in our minds.

 

I'm sure someone can explain better than me, but thats the basic gist of it.

[JaKiri]

Here you go then:

 

The balls interact through electromagnetic repulsion. That's what creates the illusion of solidity.

 

The carrier particle of EM-repulsion is (You guessed it!) light.

 

Which travels at the speed of light.

 

TADAA.

[BPHgravity]

Okay, I think I see what you are saying. Lets take Blike's example then. Lets say I have a giant spinning wheel a light minute across.

 

I am in space, so I can easily turn it. I give it a spin and appearantly the motion of the wheel a light minute away is instantaneous.

 

Does this eliminate EM-repulsion considering it is now a single body?

[JaKiri]

Originally posted by BPHgravity

Does this eliminate EM-repulsion?

 

You don't see what I'm saying.

 

All the interactions that can possibly take place do so at the speed of light.

 

The only way the next particle can know the one before it is moving is by it having a different electromagnetic field around it, wihch will change, as I have said before, at the speed of light.

 

All the carrier particles travel at c, or are theorised to at least.

 

That's why the possibility of gravitational interactions at superluminal speeds is rather perilous to Relativity, because that the speed of gravity is c is a basic idea in general, and it removes the information limit in special.

[blike]

Originally posted by BPHgravity

Does this eliminate EM-repulsion considering it is now a single body?

 

MrL's talking about EM-repulsion on the atomic level. In other words the only way one atom of an object knows what the atom's around it are doing is through their electromagnetic field. Electromagnetic fields travel at the speed of light.

 

When you move shake the stick (or spin the wheel), the reason the atoms at the other end of the stick move is because of the changing electromagnetic fields from one atom to the next. Its a chain reaction moving down the stick. EM-fields interact at speeds of C. So essentially you have a speed limit on how fast the wave of motion can travel down the stick. This motion seems like it would be instantaneous because of the short distances with which we usually interact. But if we were to measure very precisely even the shaking of a stick or spining of our car tires, it wouldn't be quite instantaneous.

 

Have you ever held one end of a rope up in the air, then suddenly pulled it down and watched the subsequent wave of motion? Thats what it would look like on a large scale.

[blike]

But what if we stretched a fundamental particle out and did it

 

hehe

[BPHgravity]

Originally posted by blike

Have you ever held one end of a rope up in the air, then suddenly pulled it down and watched the subsequent wave of motion? Thats what it would look like on a large scale.

 

No, but I have slurped a long noodle into my mouth and saw what you are describing!!

 

Thanks, this was great information! I now have a good basis and working model of how electricity works, which is the real question behind the question.

 

When EMF is applied, the electrons start to flow because of EM-repulsion. The electrons don't really move all that fast or far, but the carrier particles are at near or at the speed of light and this is the particle responsible for electrical energy. Sound okay or is electricty a different concept?

[JaKiri]

Oh, the electrons move exceptionally fast, just not all that much in a set direction.

 

ps. Fundamental particles have volume now?

[blike]

Originally posted by BPHgravity

No, but I have slurped a long noodle into my mouth and saw what you are describing!!

 

When EMF is applied, the electrons start to flow because of EM-repulsion. The electrons don't really move all that fast or far, but the carrier particles are at near or at the speed of light and this is the particle responsible for electrical energy. Sound okay or is electricty a different concept?

 

Haha, I'm sure you've done the rope thing. Like cracking a whip except with a long piece of rope.

 

I don't know too much about the physical processes of electricity, but I'll take a stab at the general principle behind it.

 

There aren't really "carrier particles". Its the EM field between the electrons. Imagine all the atoms in a copper wire lined up. The electrons around the atoms would be like the tennis balls in your thought experiment. While the FLOW of electrons from one atom to the next is rather slow, when one of them changes position, it effects electrons all the way down the wire at near the speed of light, because of the electromagnetic fields between them interact with each other at the speed of light.

[greg1917]

electrons themselves move through a conductor very slowly. as metals exist as a large positive lattice 'swimming' in a sea of delocalised electrons, the electrons cannot move in a straight line through the conductor anyway. they move in a zig zag pattern, colliding with atoms. the drift speed is somewhere near a quarter of a mm per second for a wire of radius 1 mm and a current of 10A.

[blike]

oh, and I stand corrected on a previous comment i made.

 

From another thread MrL mentions:

 

"The carrier particles exist for the four basic forces, which are:

 

The Electromagnetic

The Weak Nuclear Force

The Strong Nuclear Force

Gravity."

 

and then here I said "There aren't really "carrier particles"."

 

oops

[M-CaTZ]

YO I HEARD TENNIS BALLS. WHO WANTS TO PLAY