Still faster than light?

[Vikrant94]

Hi, I was reading the thread previously posted on faster than light, I don't know why it's been locked. I didn't understand this myself. What does it mean to say there seem to be ways for something to go faster than light... but not convey information?

What about this arrangement: Consider two rods, intersecting at their midpoint, making an angle \theta0with each other. If one rod is held fixed along the x-axis, and other rod moves down with a constant speed v0 (less than c) speed (without changing its slope), we find that the point where they meet moves with a speed v=v0[b/h] (see figure), which can be adjusted arbitrarily, until v is more than c. Can't we transfer information this way?

Also.. isn't something to be considered about the nature of the rods in these cases? For example, imagine two people, P and Q, standing 1 kilometer apart. A rigid rod, 1 km long, connects them. P fires a signal (at c) towards Q. If he nudges this ideal rigid rod, Q will feel the nudge immediately, thus knowing a signal has been sent, before the signal arrives! I think what is overlooked is that anything is made up of atoms, held together by various forces, so there is always a time delay in "maintaining rigidity", that is, moving a long rod at one end means for some time, its length will change, or the information will be transferred through some sort of wave, whose speed must be <= c. But this length need not be 1 km, it could be the width of a proton even, which is another way of showing maybe the invalidity of the rigid particle nature of any elementary particle?

[A.T.]

What about this arrangement: Consider two rods, intersecting at their midpoint, making an angle \theta0with each other. If one rod is held fixed along the x-axis, and other rod moves down with a constant speed v0 (less than c) speed (without changing its slope), we find that the point where they meet moves with a speed v=v0[b/h] (see figure), which can be adjusted arbitrarily, until v is more than c. Can't we transfer information this way?

No


I think what is overlooked is that anything is made up of atoms, held together by various forces, so there is always a time delay in "maintaining rigidity",
Yes, there are no perfectly rigid bodies. The information will travel at the speed of sound for the given material.

[DaleSpam]

What does it mean to say there seem to be ways for something to go faster than light... but not convey information? As JesseM said in the other thread, no thing goes faster than light in any known FTL scenarios. A laser dot may sweep from point A to point B FTL, but the photons in the laser all traveled at c, and the dot cannot be used to transmit information from A to B.

[San K]

Hi, I was reading the thread previously posted on faster than light, I don't know why it's been locked. I didn't understand this myself. What does it mean to say there seem to be ways for something to go faster than light... but not convey information?

What about this arrangement: Consider two rods, intersecting at their midpoint, making an angle \theta0with each other. If one rod is held fixed along the x-axis, and other rod moves down with a constant speed v0 (less than c) speed (without changing its slope), we find that the point where they meet moves with a speed v=v0[b/h] (see figure), which can be adjusted arbitrarily, until v is more than c. Can't we transfer information this way?

Also.. isn't something to be considered about the nature of the rods in these cases? For example, imagine two people, P and Q, standing 1 kilometer apart. A rigid rod, 1 km long, connects them. P fires a signal (at c) towards Q. If he nudges this ideal rigid rod, Q will feel the nudge immediately, thus knowing a signal has been sent, before the signal arrives! I think what is overlooked is that anything is made up of atoms, held together by various forces, so there is always a time delay in "maintaining rigidity", that is, moving a long rod at one end means for some time, its length will change, or the information will be transferred through some sort of wave, whose speed must be <= c. But this length need not be 1 km, it could be the width of a proton even, which is another way of showing maybe the invalidity of the rigid particle nature of any elementary particle?

as mentioned previously....the information across the rod will move much slower than the speed of light....from atom to atom in the rod....

however somethings do seem to move faster than light. for example:

law of conservation of momentum, properties such as spins/polarizations etc....and that too between very small particles...such as photons, electrons etc

however the above cannot be used to transmit information....

[Naty1]

I didn't understand this myself. What does it mean to say there seem to be ways for something to go faster than light... but not convey information?

I'm not sure it IS "understandable"....any more than that light is the fastest anything can go.
I still can't "understand" that everybody measures the same speed for light...seems crazy, and it IS crazy...yet correct.

And after fruitless attempts to circumvent this limit, eventually we conclude "ok, its a fact",
When scientists try experiments, say trying to take advantage of the laser dot Dalespam described "moving faster than light" they eventually come to the conclusion that none of the components (photons, electromagnetic waves, etc) are themselves move FTL. The dot flashes first in one spot and a moment later in another at FTL speed, yet you can't send a signal along the beam and move it from A to B FTL....

Nick Herbert has an inexpensive softcover book FASTER THAN LIGHT, Superluminal loopholes in Physics.....I did not find it especially insightful, but he has dozens of apparent exceptions to FTL and "explains" them away,,,,like the laser dot....