Super Slo Mo Slinky Demonstrates Why a Pole Push Won't Go Faster Than Light.

reply to post by Biigs

The wave is the first electron moving to the next atom and the electron knocked off the atom goes to the next one and so on till it gets to the end after many many electrons have swapped to the next atom. The speed of the wave, i would guess is some where in the neighborhood of the speed of light.

But I don't exactly think it works by each electron knocking the next one forward. The electrical potential exerts some sort of force on all the electrons at the same time... or something like that.

The only thing which might be able to travel faster than the speed of light, would be changing a gravity field - would that be instantly detected a light year away or not?

That's an open question really. We were discussing it along with other related topics just the other day in this thread:
Quantum interaction: 10,000 times faster than light

How does one reconcile the fact that in the first video the bottom of the slinky starts to rotate well before the wave gets to the end so there is some information that is propagating ahead of the wave. The bottom of the slinky is not exactly still and the closer the wave seems to get, the faster the rotation is.

Bear with me... I am still on my first pot of coffee...

Originally posted by Korg Trinity


If you were to build a pole of immense strength, of the most densest of materials you could make an object from. Then if you were to make this pole very very long, say from here to say one light year away.
What would happen if you pushed one end of the pole, in your mind’s eye the other end of the pole would also move as you pushed, this way you could send information faster than light….

WRONG….

The reason this doesn’t work is due to the fact that information in the traditional sense does not travel faster than light. So when you push at one end of the pole, the information has to travel down the pole and you get something called a compression wave down the pole, if you like when you push the pole what you are doing is sending a wave down the pole to the other end.

No No No, I'm not buying that. You could make this pole 10 light years across and the Only thing that will effect the speed is the speed in which the pole is pushed. Size matters not. Your not sending information, you pushing a physical object. There is No wave. There is No wave compression.

Imagine a pencil on the table. If you push it, are you creating a wave and directing it to move along the pencil to the other end before the pencil moves? No your not.You are moving the entire structure through space at the same time.

So, yes, your first paragraph is indeed wrong (or right rather) , but wrong (or right rather) or the wrong reasons.Your slinky in contrast is not a ridged object but one which is springy. The kinetic energy from the top part being dropped HAS to take some time to reach the lower part of the slinky - otherwise, gravity could not take over - that lower part in fact has not been "released" until this happens - it's still being held up by the energy in the springs above it until they collapse . If the slinky were a pole...

reply to post by JohnPhoenix


No Trinity is correct, there's so much mass in a pole which is a light year long that it's impossible to push all of the mass at once, even if it was just an atom thick. The pole must compress because the force applied simply cannot push the huge amount of mass in front, and a compression wave would travel though it.

Originally posted by JohnPhoenix

Imagine a pencil on the table. If you push it, are you creating a wave and directing it to move along the pencil to the other end before the pencil moves? No your not.You are moving the entire structure through space at the same time.

Just because you cant notice it, does not mean that compression wave isnt there. It travels extremely fast, varies depending on the material the pole is constructed from.

All matter compresses and until you can make a pole out of something thats not matter, you wont be able to ever transmit information faster than light.

Would you guys listen to yourselves? Your creating an imaginary object that cannot possibly exist and your telling me, it is impossible to push this imaginary object with sufficient imaginary force to move it.

Besides, I don't think you saw the rest of my post. I have a problem with his slinky metaphor.

WHY would you even have to push the pole? You don't. This pole could be moving under it's own power just floating through space - you know once you set an object in motion it will stay in motion unless acted on by an equal or greater force - why then would this pole still have this compression wave? I don't think it would. I think it's an unproven theory - and a bad one at that.

You guys maintain you would not be moving the object faster than light ( i never had a problem with that part) So lets say this pole is 1 light year long, and you pushed it or set it in motion, 3 light years ago... so what happens to your compression wave? Surely it's not still traveling to the end of the pole when the pole started moving 2 light years ago...

isnt the bottom of the slinky falling, its just that the tension from the coils above it is keeping it in the air kinda like the two forces cancelling each other out. until the majority of the slinky hits the bottom of the slinky adding extra weight and at the same time reducing the force holding that was holding the bottom up.

i dont know the interaction rates between molecules but i imagine they would be instantaneous or at least at the speed of light.

reply to post by JohnPhoenix

This pole could be moving under it's own power just floating through space - you know once you set an object in motion it will stay in motion unless acted on by an equal or greater force - why then would this pole still have this compression wave? I don't think it would.

Yes but the point is to transfer information faster than light, and if it's moving on its own then that's not possible. Of course you can get the whole thing moving through space, but that achieves nothing useful.

You can transmit information (in this case the push or twist of a pole) faster than the speed of light IF the material had atoms that actually touched each other - this is impossible in our universe.

Since matter has "spaces" between atoms and the forces keeping the material together electromagnetic, anything you do to one end of the pole has to skip from atom to atom all the way down the pole to the other end, this will always be slower than the speed of light, which is the limit of the electromagnetic force. At best you could get the info as fast as the speed of light, but faster than light while you are in this universe using real matter, cant be done.

Originally posted by JohnPhoenix
Would you guys listen to yourselves? Your creating an imaginary object that cannot possibly exist and your telling me, it is impossible to push this imaginary object with sufficient imaginary force to move it.

Besides, I don't think you saw the rest of my post. I have a problem with his slinky metaphor.

WHY would you even have to push the pole? You don't. This pole could be moving under it's own power just floating through space - you know once you set an object in motion it will stay in motion unless acted on by an equal or greater force - why then would this pole still have this compression wave? I don't think it would. I think it's an unproven theory - and a bad one at that.

You guys maintain you would not be moving the object faster than light ( i never had a problem with that part) So lets say this pole is 1 light year long, and you pushed it or set it in motion, 3 light years ago... so what happens to your compression wave? Surely it's not still traveling to the end of the pole when the pole started moving 2 light years ago...

edit on 1-4-2013 by JohnPhoenix because: adition

(A light year is a measure of distance not time.)

The compression wave is moving at the speed of sound, because that's what sound is.

The speed of sound in steel is 6100 m/s, so to propagate a compression wave 1 light year (9.46 x 10^15 m) takes just under 50,000 years. So if you started pressing at the beginning of human civilization you'd be 1/5th of the way done by now.

Originally posted by ChaoticOrder
reply to post by JohnPhoenix

 

No Trinity is correct, there's so much mass in a pole which is a light year long that it's impossible to push all of the mass at once, even if it was just an atom thick. The pole must compress because the force applied simply cannot push the huge amount of mass in front, and a compression wave would travel though it.

This is a true fact, but it doesn't rely on an extremely massive pole, it happens with any solid material.

Originally posted by Korg Trinity

Originally posted by jiggerj
reply to post by Korg Trinity

 

Hmmm, if you push one one end of a pole a lightyear long, would the energy you put into it just be absorbed by the pole and never reach the other end?

I'm thinking shock absorbers on a car. You hit a pothole, the shock absorbers take in this energy, and then where does that energy go from there?

"for every action there is always an equal and opposite reaction" - Newtons Law of Motion.

In the case of the shock absorber, what you have is a cushioning effect, but the actual energy is stored in the spring, then released once more. The energy is not absorbed, just redirected.

Korg.

Actually this is not the case. If this was the case, the car would continue to bounce up and down forever after you hit the bump. What is happening is that there is a damping effect, which is converting the energy into heat.

Originally posted by pheonix358
There are two forces at work. The bottom of the slinky is held in place by the top of the slinky. When you release the top, the bottom is still held by the 'springiness' of the rest. As the top falls it releases the 'springiness is elasticity) as it falls.

An infinitely dense pole would have no elasticity and thus may move instantly in you example.

P

That's the way I see it too..! If you don't compress but stay rigid, any part of the length of the pole is moot, it's the distance moved that would count. Say the distance moved is one foot, if you move the one foot however fast, that translates to one foot at the other end moving the same speed in that one foot.

Originally posted by Biigs
You can transmit information (in this case the push or twist of a pole) faster than the speed of light IF ...

No you can't.

**

We already know that LS is the upper limit of how to transfer information (at least according to our current status quo of science) - even through a vacuum or a electric wire etc.

NOW...in your example you actually add another hurdle, you turn it into a physical experiment where a force would have to travel "physically" through/along the pole...and claim that it would somehow enable to beat the limit of LS.

If anything, LOGIC says that sending a pushing force through the pole would require MUCH MORE TIME than sending a beam of light through the vacuum of space.

reply to post by flexy123


Try again please. Granted that the outcome is debatable, but you do not understand the question being asked. It is not a pulse, it is the whole pole being moved.

Of course it will not work in the real universe but the theory of the question is quite valid. We just can not build the infinitely dense pole we require and if we could we would never move it because its mass would also be infinite.

May I suggest you examine the question some more.

P

Originally posted by Korg Trinity

If you were to build a pole of immense strength, of the most densest of materials you could make an object from. Then if you were to make this pole very very long, say from here to say one light year away.
What would happen if you pushed one end of the pole, in your mind’s eye the other end of the pole would also move as you pushed, this way you could send information faster than light….

WRONG….

I believe the reason the pole can not transmit information faster than the speed of light is because the motion propagates through the material at the speed of sound for that material. So if we were to say that the density of the pole is infinite, then the speed of sound travelling through the material would be equal to the speed of light. If that were the case then the motion would reach the other end of the pole in one year. If the pole is less than infinitely dense, it would happen slower.

I realize this is pretty much what the op is saying, I just wanted to point out the speed of sound part.

Ok, but you had stated a material of the densest material so how about instead of dangling a slinky, hang a broom stick over the ledge of a building. I THINK when you let go of the broom stick, whatever happens to the "user" end will immediately do the same to the opposite end.

Originally posted by pheonix358
reply to post by flexy123

 

Try again please. Granted that the outcome is debatable, but you do not understand the question being asked. It is not a pulse, it is the whole pole being moved.

Of course it will not work in the real universe but the theory of the question is quite valid. We just can not build the infinitely dense pole we require and if we could we would never move it because its mass would also be infinite.

May I suggest you examine the question some more.

P

You obviously don't understand

Even if we would be ABLE to build this perfect pole with all the atoms lined up, we wouldn't be able to do it.
UNLESS - you are the first person on Earth who proved Einstein wrong with a rather simple thought experiment.

LS is either the upper speed limit of any event/information or it isn't. If LS is the limit, then also the "perfect pole" cannot make information traverse faster, even if the perfect pole is only a thought experiment. Doesn't matter. You either stick to relativity or you don't. You cannot say LS is the upper limit of any information's speed and then come up with an exception scenario where it wouldn't apply

EDIT: Feel free tho to demonstrate/proof that it works, assuming we have a "really long" pole with all atoms lined up. If you manage to do it, I'd also recommend filing for a patent QUICKLY and I'd personally recommend you for the noble prize in physics

You don't need a long pole for the experiment. In fact, an object of ANY size and shape will work. Distance over time calculation doesn't require any crazy engineering or long poles. It's only math.

Hell, even a single tron would work for the measurement.

C is not constant though. That has been demonstrated. en.wikipedia.org...

So you have to specify the conditions under which you measure C, and what specific value you are claiming a signal cannot exceed.

hate to burst your bubble but the slinky does fall with gravity at the same time the collapse is happening, it just a trick of the eye coupled with the slow motion camera. He does actually state this is happening in the first video in a round about way when he explains the purpose of the red circle in the animation. If you watch this red circle which you could consider to be gravity, you can see it moving down with the slinky before the collapse reaches it. If you look even closer and pick a point of reference on the wall of the building you will see the bottom end of the slinky move past that point meaning gravity does indeed effect the whole slinky.

Sorry if you weren't implying this just thought I would make that perfectly clear for everyone.