Weird physics question

[the_tyrant]

I was sitting there, and i just had a weird idea
imagine 2 points a and b
the distance between a and b takes light 1 minute(or any amount of time) to travel
there is a tense piece of string connecting point a and b
hypothetically, if a light was shined from point a to point b and that the string was pulled at point a at the same time, what would we felt at point b first?
the light or the pull on the string?

or a better restatement would be, does light travel faster, or does a piece of mass travel faster?:hmmm:

edit: Rephrasing the question: solid mass vs light, what would be felt on the other side faster?

[Spike88]

I'm pretty sure the string will not travel at the speed of light, unless it has Star Wars light-speed drives :P.


Also if it takes 1 minute for the light to travel, the string will most likely fall limp before it can even reach the end. Unless it was in a vacuum, but even then light travels fastest.


Edit: And thinking about it. Nothing can go the speed of light(besides Light) anyways.

[TLAM Strike]

Edit: And thinking about it. Nothing can go the speed of light(besides Light) anyways.

Nothing can accelerate faster than light. Objects already moving faster than light can exist.

[Gargamel]

Two ways to look at it:

1) Like sound under water, the energy in the string has a speed through a medium. It is slower than light. Hence we will see the light first.

or

2) The string can be considered a solid object when stretched to its maximum, ie no more stretch is possible. So when one end is pulled, the other end immediately moves too, and is therefore 'faster' than light. But this is not truly going faster than light, as nothing is moving from end to another, it's just an object beginning to move.

[Buddahaid]

Two ways to look at it:

1) Like sound under water, the energy in the string has a speed through a medium. It is slower than light. Hence we will see the light first.

or

2) The string can be considered a solid object when stretched to its maximum, ie no more stretch is possible. So when one end is pulled, the other end immediately moves too, and is therefore 'faster' than light. But this is not truly going faster than light, as nothing is moving from end to another, it's just an object beginning to move.

Ah, but the cause and effect is then instantanious and faster than light. FTL communication via the cans and string?
:DL

[Gargamel]

Ah, but the cause and effect is then instantanious and faster than light. FTL communication via the cans and string?
:DL

No, because then you are in situation 1, where energy is traveling along the string in a wave.

What is 'possible', though, is to build a 'stick' of great length, but it's internal components must be completely static, and then you could kind of swing it back and forth and do a morse code over great distances. But there are two problems with this:

1) For this to be faster and more practical than light speed transmissions, ie radio waves and the like, the 'stick' would have to be of immense length. Off the top of my head, the minimum would have to be something like the distance from Jupiter to the sun, or Earth if you like, around 5-6 AU (500,000,000 miles or so). This alone makes it impractical to build and maintain, let alone finding the energy to move such a mass, and then stop it after only a few inches of movement.

2) Even the electron bonds of the component molecules are not static, and have some give to them. Thus you would get some accordion type effect within it's structure. Thus, it would not be a solid object, but a string transmitting waves.

This type of transmission could only be of the morse code type, 1's and 0's, complex data streams would be practically impossible.

Nothing is technically moving faster that light, aside from the information contained in a forward/back position.

[Buddahaid]

1 and 0 makes for binary language. It's then a question of frequency for the very long string.

[Gargamel]

Nothing can accelerate faster than light. Objects already moving faster than light can exist.

Close, but nothing can accelerate to the speed of light. Using relativity, it requires an infinite amount of energy (more than is in the known universe) to accelerate an object to the speed of light. The faster you go, the more mass an object has, requiring more energy to go faster.

An object already going light speed, could in theory stay at that speed if they don't encounter any drag. In that same theory, objects could go faster than the speed of light, IF they began that way. But where would such objects come from?

[Gargamel]

1 and 0 makes for binary language. It's then a question of frequency for the very long string.

Yup. The object isn't moving very far or very fast, it's just moving it's other end a little bit, but very very far away.

But the practical aspect is, the higher the frequency, the more energy is needed to reverse the object for the next datum to be sent. But then your starting to break other laws of physics by trying to find enough energy to do that. Ie, can't find enough energy.

But, if you could make this object almost massless, then you could have a high enough frequency to transmit a good bit of data.

[Buddahaid]

A pure energy string of limitless length vibrating at less than the speed of light. I'll hold my breath.

[Castout]

There's no weird questions only weird answers :O:

[Castout]

2) The string can be considered a solid object when stretched to its maximum, ie no more stretch is possible. So when one end is pulled, the other end immediately moves too, and is therefore 'faster' than light. But this is not truly going faster than light, as nothing is moving from end to another, it's just an object beginning to move.

That . . . .assuming both started at the same time.

[UnderseaLcpl]

Nothing can accelerate faster than light. Objects already moving faster than light can exist.

Granted, I'm no expert on physics, but I disagree - at least until you can explain it.

The way it was explained to me is that objects travelling at relativistic speeds undergo corresponding shifts in mass (as gargamel states), as well as relative time and dimension. Even if you somehow had two particles of anything approaching each other at the speed of light, their speed, in any frame of reference, even when added together, is still c.

--------------------------------------------

As far as the string question goes, the answer is, quite definitevely, that the light would reach its destination long before the molecules in the string resonated from one end to the other. Atoms have mass, and the distance atoms in anything must travel before repelling each other (once energy is imparted) is quite far in terms of scale.

The effect of plucking a string, no matter how taut, would still require the acceleration of every atom, and the force transmitted would decrease with distance travelled, so the light would get there first.

[Buddahaid]

If the signal was a wave. I'm saying what of a hypothetical string that has no mass, and no elasticity, and is moved as one massless length allowing binary language over limitless distance. No mass requires a pure energy object of some form that is imune to time.

Not for me to to proof! :shucks:

[Aramike]

I was sitting there, and i just had a weird idea
imagine 2 points a and b
the distance between a and b takes light 1 minute(or any amount of time) to travel
there is a tense piece of string connecting point a and b
hypothetically, if a light was shined from point a to point b and that the string was pulled at point a at the same time, what would we felt at point b first?
the light or the pull on the string?

or a better restatement would be, does light travel faster, or does a piece of mass travel faster?:hmmm:Concurring with an earlier answer, the string would be felt first.

The difference is simple: light would have to travel the distance that the string as already traveled.

[Raptor1]

Granted, I'm no expert on physics, but I disagree - at least until you can explain it.

The way it was explained to me is that objects travelling at relativistic speeds undergo corresponding shifts in mass (as gargamel states), as well as relative time and dimension. Even if you somehow had two particles of anything approaching each other at the speed of light, their speed, in any frame of reference, even when added together, is still c.


It would be impossible for ordinary matter to travel at speeds greater than light speed, because the energy required to accelerate anything with mass to c is infinite. However, there are (theoretical) particles that always travel faster than light, and would similarly require an infinite amount of energy to slow down to light speed.

[TLAM Strike]

Granted, I'm no expert on physics, but I disagree - at least until you can explain it.

Just google 'Tachyons'

I'll leave it at that because everything beyond that makes my head hurt.

[Herr-Berbunch]

Edit: And thinking about it. Nothing can go the speed of light(besides Light) anyways.

Dark can travel at the speed of light! Everybody seems to miss this part out. :know:

[Diopos]

Forces "propagate", too.
Absolute "inelastic" bodies which allow instant force propagation are fictional objects as much as Newton's "point masses" (where all mass of an object is condidered to be confined in a dimentionless point).

In the OP light would reach point B before it felt points A pull.

At least I think it would...

.

[Diopos]

...
An object already going light speed, could in theory stay at that speed if they don't encounter any drag. In that same theory, objects could go faster than the speed of light, IF they began that way. But where would such objects come from?

The future ? :hmmm:

:doh:

.

[tater]

For a vibration in the string, the speed depends on the mass and tension on the string (it's a transverse wave). It will be less than c.

For a pull, the string will stretch, and then the wave propagates like sound (longitudinal wave) and will move at the speed of sound in the media.

BTW, doesn't matter if you replace the string with a neutronium rod. Still takes time (more than light) to propagate.

[the_tyrant]

For a vibration in the string, the speed depends on the mass and tension on the string (it's a transverse wave). It will be less than c.

For a pull, the string will stretch, and then the wave propagates like sound (longitudinal wave) and will move at the speed of sound in the media.

thanks:salute:

[TLAM Strike]

The future ? :hmmm:

:doh:

.

Actually you are right. As I understand it Tachyons travel back in time as they travel faster than c.

[Diopos]

Actually you are right. As I understand it Tachyons travel back in time as they travel faster than c.

I know. I was born in 2055. !

:D

.

[Aramike]

It should be noted that tachyons themselves are highly speculative, theorized particles.

[Raptor1]

It should be noted that tachyons themselves are highly speculative, theorized particles.

Of course, but I think the point was that relativity doesn't actually forbid something from going over the speed of light, you just can't accelerate anything to the speed of light in the first place.

[Gargamel]

BTW, doesn't matter if you replace the string with a neutronium rod. Still takes time (more than light) to propagate.

But thats not the point, the hypothetical string has no stretch and is completely static. A stick with infinite length, no stretch, and no flex, the moment one end is moved, the other moves too.

[frau kaleun]

Actually you are right. As I understand it Tachyons travel back in time as they travel faster than c.

Yes, and the term itself derives from the word "tacky," which means both "sticky to the touch" and "tasteless." As tachyons move backwards through time they stick to whatever bits of the past they can find, rendering those items garish and unfashionable to the eyes of the present.

Those of you who are old enough to have a picture of yourself in a plaid polyester leisure suit or gold lamé parachute pants will know what I'm talking about. :yep:

[Diopos]

But thats not the point, the hypothetical string has no stretch and is completely static. A stick with infinite length, no stretch, and no flex, the moment one end is moved, the other moves too.

Relativistic length contraction: Link (http://en.wikipedia.org/wiki/Length_contraction)
Or to put simple, in the end, light always wins! :yep:

Until the next theory is discovered ... :hmmm:

,

[Gargamel]

Relativistic length contraction: Link (http://en.wikipedia.org/wiki/Length_contraction)
Or to put simple, in the end, light always wins! :yep:

Until the next theory is discovered ... :hmmm:

,

From your Link:

This contraction (more formally called Lorentz contraction or Lorentz–Fitzgerald (http://en.wikipedia.org/wiki/George_FitzGerald) contraction) is usually only noticeable at a substantial fraction of the speed of light (http://en.wikipedia.org/wiki/Speed_of_light);...........At a speed of 13,400,000 m/s (30 million mph (http://en.wikipedia.org/wiki/Mph)), the length is 99.9% of the length at rest; at a speed of 42,300,000 m/s (95 million mph), the length is still 99%

Since we are dealing with speeds of no more than that of pushing a pencil, lengthwise, across a table, this theory has no application in this scenario.

[Aramike]

Of course, but I think the point was that relativity doesn't actually forbid something from going over the speed of light, you just can't accelerate anything to the speed of light in the first place.That's true for anything with information or mass. However, we can routinely violate c regarding massless particles and radiation.

[Diopos]

From your Link:



Since we are dealing with speeds of no more than that of pushing a pencil, lengthwise, across a table, this theory has no application in this scenario.

In the link (http://en.wikipedia.org/wiki/Length_contraction#See_also), paragraph "Paradoxes" as regard to the concept of rigid bodies.

.

[TarJak]

I may be wrong, but the string in the OP exists at both points a and b at the same time. Depending on the relativity of the observer, the light will either arrive before, after or at exactly the same time as the string movement is felt. It's all relative.:D

[Raptor1]

That's true for anything with information or mass. However, we can routinely violate c regarding massless particles and radiation.

Ordinary massless particles can routinly go faster than light in a vacuum?

[DarkFish]

http://files.sharenator.com/1285635395271_Physics_troll-s774x459-98034-580.jpg
http://www.sharenator.com/Physics_troll/
;)

[Aramike]

Ordinary massless particles can routinly go faster than light in a vacuum?I didn't say ordinary...

Was referring to phase velocities (and not in vacuum) and subatomic polarity shifting.

[Gargamel]

In the link (http://en.wikipedia.org/wiki/Length_contraction#See_also), paragraph "Paradoxes" as regard to the concept of rigid bodies.

.

All of the paradox's refer to objects that are undergoing length contractions. Our 'stick' is not moving fast enough to undergo this phenomenon.