narwhol - 16 October 2007 07:54 PM

No.  How could there be a delay?  I know I said sideways motion, but I just meant translational motion.  If you chose to call two of the faces of the long edge of the pencil fron and back, the up and down movement would now be a sideways movement.  What I meant was translating the pencil as a whole object from one place to another as opposed to particles within it transmitting energy as a longitudinal wave, which is lossy and slow.

Aren’t we translating the pencil as a whole object by applying a force only at one end?  We don’t get to push sideways on the pencil evenly along its length.  That would be cheating since the distance of the communication then becomes zero.

No, George would have communicated his thoughts to earth from the sun, whichever form of runes he sticks down on the paper.

Anyway, off to bed now so will continue this on thursday (won’t be around tomorrow evening)

narwhol - 16 October 2007 08:15 PM

No, George would have communicated his thoughts to earth from the sun, whichever form of runes he sticks down on the paper.

This was great, Narwhol! Thanks!

narwhol - 16 October 2007 06:54 PM

provided sufficient work is done to move the pencil from George’s end and the ends are fixed as mentioned before, the only thing that possibly can result from this is that the whole pencil is translated in the direction of the force, including the unperturbed position about which any fexural vibration is occuring.  Thus, the whole thing, which is staying together as one piece can only move in the direction of the force and since the other end is fixed wrt any flexural red herrings you’ve introduced, it moves with George’s end, without delay.

Again, since the information about the movement between the atoms of the material is transmitted by photons, which themselves move at the speed of light, I don’t see how this can occur “without delay”. Also I am wondering how what you claim can possibly be true, when it is patently obvious that one can move one end of a long steel bar from side to side without the far end moving at all. (The bridge movie makes this entirely clear). The bar flexes, because it is not perfectly rigid.

narwhol - 16 October 2007 06:54 PM

The exchange particles are continually being produced and resonating, and only over infinitessimally distances and are there throughout, rather than acting sequentially or within any time lag. because they are simultaneous.  If they weren’t you’d have one half of the pencil leaving the other half behind.  Can you not see that that is ludicrous?

This isn’t well explained at all. You will have to explain why and how the photon exchanges occur simultaneously along the entire length of the material, rather than being emitted and absorbed by each molecule in sequence.

And nobody is claiming that the pencil moves by halves; this is a straw man argument. The claim is that each molecule in the pencil moves the ones next to it; the procedure is done by the electromagnetic interactions between the particles and is not simultaneous.

As for “ludicrous”, it is ludicrous that one could move a 93 million mile long pole instantaneously. I am always prepared to be convinced; physics is definitely very strange and at times entirely counterintuitive, but you’ll need to do a heck of a lot better than that to convince me. In particular, I’d like some outside confirmation—that is, credible websites that cite the relevant theory and data.

It seems to me that we are discussing the subject of the velocity of elastic deformation in a solid.

We’re discussing deformation because in moving the pencil (or long metal rod, which makes more sense) back and forth, we are deforming it in either direction. Now, according to the online Physics forum HERE, the maximum speed of this deformation is defined as the speed of sound. It isn’t anywhere close to the speed of light, much less instantaneous.

For a moment I thought I found another way of delivering the message instantly. It’s called quantum entanglement, where something that happens to a particle in one place (sun) can be instantly reflected by one that is billions of miles away (Earth). Unfortunatelly, “quantum entanglement does not enable the transmission of classical information faster than the speed of light."* Too bad. Oh well, the pencil has to work! :grin: 

*Wikipedia

Right. There is no way to transmit information faster than light. This has been drummed into my head by any number of eminent physicists. This is the basic reason not to accept narwhol’s description of the phenomena here.

Just to repeat: we’re talking about moving a rod 93 million miles long and maybe a half-inch in diameter instantaneously, along its entire length. One couldn’t even move a rod half a mile long in this fashion: it would bend elastically close to the initial point of motion, and the bend would create a wave of motion down the rod. Further, the mass and hence inertia of a rod this size would be enormous. Moving one end back and forth would have no effect whatever very far from the point of origin.

Forget about the pencil, the rod, the bridge, or any such a unit, Doug. Let’s stay on Earth for a change. The circumference of Earth is about 40,000 km. The speed of light is about 300,000 km/s. In one second, the light can travel around Earth about 7.5 times. Now, imagine a line of billiard balls wrapped around Earth, say, 15 times (just to make the numbers even). It would take light two seconds to go around Earth 15 times. But if I pushed the first billiard ball (they are all aligned and touching each other perfectly — they are not attached to each other!) the ball at the other end of this chain (again, since the ball are not attached to each other “chain” might not be the right word here) would move simultaneously.  Why wouldn’t it? As you can see, in this case we don’t need to worry about any banding, or the mass of the moving object. And if you need to object to my experiment because of friction, imagine that instead of pushing billiard balls, I am using Harry Potter’s Quidditch balls that are floating in a vaccum.

Same issue. The motion would be transferred by compression of each ball against the next, and would travel in a wave. And it wouldn’t travel very far at all, since again, you’re talking about an enormous inertial mass of billiard balls. Likely the force you applied would be lost to heat energy within a few hundred yards.

I’m not buying any of this “instantaneous motion” stuff without some independent evidence from a very credible source.

Here is Lawrence Krauss’s . Would he answer? I am scared to try it…

You’re welcome to try, as far as I’m concerned. I tried something similar awhile ago with Victor Stenger, and I think the issues got garbled.

Would somebody here, please, help me to translate my original “pencil dilemma” question to proper English before I send it?

It seems plenty understandable as it is. Same with your billiard ball example. But you may be dealing with a very busy physicist who reads a line or two and answers the wrong thing. No way to get around that possibility, unfortunately ...

I’d suggest also sending along a URL of the thread so he can respond in it if he wants.