Transmitting Information Faster than C

[In My Memory]

I discussed this a little with YT on the SFN chatroom, and I want to know why information cant be transmitted any faster than C. I dont know if there if "information" has a special meaning in physics, so I'm going to use it as a synonym for language and communication. Specifically, I want to know if its possible to send Morse Code from point A to point B faster than 300,000 km/s.

 

I've heard of ways where objects can travel "faster" than C in a trivial sense, for instance if you wave a beam across the sky you could observe the reflected laser dot trace the surface of the moon faster than C. I've been interested in the way the contact point between the blades on a pair of scissors can hypothetically travel faster than C, like this:

 

 

The black dot marks the contact point between the blades, and you can see that the contact point travels along the blades with exponentially increasing speed. With sufficiently long blades moving at a very fast speed, I dont find it hard at all to concieve that the contact point of the blades exceeds C. So whats to prevent someone from transmitting Morse Code information faster than C?

[YT2095]

the blades will curve and the energy used to close them will need to increase beyond that which is possible.

if it has mass, it Cannot exceed C.

consider this also, as the angle (in red) becomes more acute the less force will be applied to make it move forwards, or rather the same force will apply, but not enough to keep it accelerating.

 

a bit like the old "two infinately long parralel lines will eventualy meet" idea, it simply wouldn`t work.

[woelen]

In practice indeed the blades will curve, but even if if this does not occur, then it still will become impossible. If the blades become very very long, then the end points of the blades will move with a speed closer and closer to C. The energy to accelerate them will grow and grow with increasing speed and an infinite amount of energy is needed to reach the speed C.

 

Imagine a simpler system. You have a long stick and you move it around at finite angular velocity (rotational speed), e.g. one turn per second. The end point then moves along a circle, with a speed, equal to 2*pi*R m/s, where R is the length of the stick.

Suppose you have an infinitely stiff and very long and very light stick made of the newest and coolest SciFi materials available from StarWar's chemical engineers. The stick only weighs 1 kilo, it has a length of 100000 km, and a thickness of 1 cm. Now you want to rotate this. If you manage to rotate this stick at 1 rotation per second, then the other end will move with a speed of 2*pi*100000 km/s, which is well over the speed of light. But you will feel that it is incredibly difficult to rotate the stick. The theory of relativity tells that when a mass is moving faster, then its apparent mass increases. The mass near the remote end of the stick goes very fast, even at moderate speed of rotation, and its apparent mass increases. At the speed of light, the apparent mass is infinite, and hence, the force (and also energy), needed to accelerate the mass to the speed of light will be infinite. If you were very patient and applied a rotational constant torque at the stick, then you would see that the end point approaches the speed of light, but it will never reach the speed of light. You can approach it as close as you want (given sufficient time and energy), but you will never actually reach it.

 

All this can be described very nicely by mathematical equations, but I will save you the math. It is not easy to perform the math, but sure it can be done.

 

To give you an idea of the strength of this effect:

 

A mass of 1 kilo, moving at 10000 km/s has an apparent mass of 1.00056 kilo. Even at that tremendous speed the effect only is marginal.

A mass of 1 kilo, moving at 100000 km/s (1/3 of the speed of light) has an apparent mass of 1.06 kilo.

A mass of 1 kilo, moving at 200000 km/s has an apparent mass of 1.42 kilo.

 

Even at 90% of the speed of light the effect is not that strong. The mass then would appear as 2.3 kilo. But from that point it quickly goes up, when approaching C.

 

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

 

There seems to be one way to influence particles over long distances, instantly, but this cannot be exploited to pass information over long distances. It has to do with quantum mechanics. When two particles are created and these two have a certain amount of energy together, and they move apart from each other, then when one of the particles is "fixed" in some way (e.g. its velocity), by measuring it, then the other particle also is "fixed", such that the initial energy requirement is fullfilled.

 

This experiment was performed by Alain Aspect, A French physicist. This is a very nice achievement, but it cannot be used to transfer information instantaneously over long distances.

 

http://en.wikipedia.org/wiki/Alain_Aspect

[Phi for All]

Specifically, I want to know if its possible to send Morse Code from point A to point B faster than 300,000 km/s.

I remember hearing a hypothesis that gravity may pass through all points in the universe (and other possible universes) simultaneously. Could GR be used to transmit a Morse Code message faster than C?

[In My Memory]

woelen,

In practice indeed the blades will curve, but even if if this does not occur, then it still will become impossible. If the blades become very very long, then the end points of the blades will move with a speed closer and closer to C. The energy to accelerate them will grow and grow with increasing speed and an infinite amount of energy is needed to reach the speed C.

I dont actually think thats a genuine limitation, because the end points can actually move very slowly, but the contact point between the blades will move much faster.

 

Imagine the following, we construct a pair of blades 5000 m long, where the back ends of the blades are level, and the front ends of the blades are seperated by 1 m:

 ___________________5000 m_____________________________
/                                                      \

                                           ----------- }
                                -----------            }
                     -----------                       } 1 m
          -----------                                  }
-*---------                                             }
-*-------------------------------------------------------
^
|
Contact point

Its probably not very easy to see with ASCII art, but if you close the blades (the ends move a total of 1 m), the contact point travels 5000 m. So if the blades close at 1 m/s, then the contact point moves along the blades at an average speed of 5000 m/s. You never have to worry about the end points of the blades moving anywhere close to C at all

[YT2095]

lemme see if I got this straight, you`re on about this ""Contact point"" are you thinking of 2 objects meeting on collision, both at just over half C?

[In My Memory]

YT,

lemme see if I got this straight, you`re on about this ""Contact point"" are you thinking of 2 objects meeting on collision, both at just over half C?

Not exactly. I'm talking about the place where two blades come into contact with one another, when they swing across each other like scissors.

 

I think everyone else had the idea that I was asking whether a blade could be swung so fast its end point exceeds C, but thats not what I was talking about in the first place. I'm only talking about the place where the blades come into contact, as indicated by the nifty animation from the opening post

[YT2095]

so for instance the both blades open at 90 degrees start point, to close to 0 degrees.

both blade tips moving at just over half C relative to an imaginary line drawn at 45 degrees exactly in the middle of their start angle.

so relative to this line, both at say 60% C, the Net speed of meeting at the tip would be 120% C.

 

yes?

[In My Memory]

YT,

so for instance the both blades open at 90 degrees start point' date=' to close to 0 degrees.

both blade tips moving at just over half C relative to an imaginary line drawn at 45 degrees exactly in the middle of their start angle.

so relative to this line, both at say 60% C, the Net speed of meeting at the tip would be 120% C.

 

yes?[/quote']

I dont think you understand that I'm not trying to make the tip of the blades move faster than C, or even the combined speed of the blades.

 

Heres what I'm talking about:

 

 

That contact point moves up and down the blades when you open or close the scissors, and it moves much much faster than the blades themselves because it has to travel along the whole length of the blades in the time it takes to close or open the scissors. A pair of 300 km long scissors, that are only opened 1 m, the scissor blades move 1 m to close, but the contact point moves 300 km in the same time. If you closed those blades very very fast, and also made the blades much much longer, then the contact point can travel along the length of the blades faster than C without any problem.

[Royston]

The trouble is the contact point doesn't finish the journey until the end points have met. So if hypothetically you had two beams of light, and you sent a message by crossing the two beams at the speed of light, the message won't get there before the two ends have met.

 

Although the contact is travelling a farther distance, than the accumalated distance between the two beams, it's not actually travelling faster than the speed of light....otherwise it would get there before the beams meet at the end.

 

Is that right ?

[insane_alien]

again it would be limited to just below c since the force applied to the pivot to close the blades travels at the speed of light, if you had blades 1 light year long then the tips would feel no effect until 1 year after the blades started closing so the time taken to close the blades woul be just greater than 1 year.

 

if the speed of light was not a limit then this could be done

[YT2095]

A pair of 300 km long scissors' date=' that are only opened 1 m, the scissor blades move 1 m to close, but the contact point moves 300 km in the same time. If you closed those blades very very fast, and also made the blades much much longer, then the contact point can travel along the length of the blades faster than C without any problem.[/quote']

 

no it can`t.

[Cap'n Refsmmat]

This has been discussed before.

[woelen]

IMM, now I understand what you mean with your scissors experiment of thought. However, the closing of the scissors is created by means of atomic interactions. Even if you have an insanely stiff set of scissors, the forces still have to interact by means of atoms. Atom A pushes atom B, which pushes atom C, and so on. These pushes, however, are due to electrostatic forces from the electrons "orbiting" the atoms. These forces are wavelike and of electromagnetic nature, which does not go faster than light.

 

Even if the scissors were made of pure neutronium, then the forces probably would not be of an electromagnetic nature, but they would be of the type, which are active in the nuclei of atoms. But these forces also are wavelike and cannot go faster than light.

[abskebabs]

How about if you have 2 quantum particles that are entangled and coupled to the same wavefunction? When a property of one of them is measured, the wavefunction collapses, and the 2nd one instantly is endowed with the corresponding property. This property is nonlocal, and although there is no real "transmission" of information, the time it takes for the information to be known is not limited to the time it takes for light to travel the distance between the particles. In this sense, the interaction is instantaneous. Could this be used to transmit information instantaneously? Are they planning on using this in the development of quantum computing.

 

P.S sorry woelen, I should have read your post, you've already mentioned this... but I'm not fully convinced that this couldn't work.

[Cap'n Refsmmat]

How about if you have 2 quantum particles that are entangled and coupled to the same wavefunction? When a property of one of them is measured, the wavefunction collapses, and the 2nd one instantly is endowed with the corresponding property. This property is nonlocal, and although there is no real "transmission" of information, the time it takes for the information to be known is not limited to the time it takes for light to travel the distance between the particles. In this sense, the interaction is instantaneous. Could this be used to transmit information instantaneously? Are they planning on using this in the development of quantum computing.

No, it cannot be used to transmit information. Measuring the properties of one of the atoms does not transmit any usable information - you cannot tell the person with the other atom "if the spin is in this direction, I'm sending the letter A" because you cannot manipulate the atom and have that information transmitted to the atom at the other end. All you can do is measure its properties.

[bascule]

I remember hearing a hypothesis that gravity may pass through all points in the universe (and other possible universes) simultaneously. Could GR be used to transmit a Morse Code message faster than C?

 

I was interested in gravity wave communication for a long time (it was what the bass player for Iron Butterfly was working on before he mysteriously disappeared, *gasp*!)

 

But I believe GR predicts that gravity propagates at c, and this has been confirmed experimentally, although I believe the results of that experiment are still in question.

[ecoli]

I was interested in gravity wave communication for a long time (it was what the bass player for Iron Butterfly was working on before he mysteriously disappeared, *gasp*!)

 

love that band

[swansont]

The two blades need not be connected. As such, there is no causal relationship between the position of two, so there is no limit to how fast the contact point (or apparent contact point) can move.

 

It's similar to a light beam from a source rotating at [math]\omega[/math]. The speed of the projected beam is [math]\omega r[/math], so if you are far enough away, this can exceed c. But there is no information contained there, and the photons do not have a causal relationship.

 

It is always possible for two (or a series of) unrelated events to be temporally separated by less than t = d/c

[Rocket Man]

i read somewhere that a bunch of uni students designed some weird ceramic that a particular audio signal could have portions of the harmonics accellerated FTL over a distance of 5 or so atoms, i think this was a theoretical model like a simulation, so either the maths need rewriting, or something weird is going on.

 

i also read that quantum entaglement can be detected and an experiment was sucessfully performed using the collapse of entangled electrons to transmit enough information for a simple bank transaction instantly over any(?) distance.

[5614]

could have portions of the harmonics accellerated FTL over a distance of 5 or so atoms

Could be something called anomalous dispersion which is not actually FTL although it can look it at first sight, when you look more deeply at what is happening it is not.

 

i also read that quantum entaglement can be detected and an experiment was sucessfully performed using the collapse of entangled electrons to transmit enough information for a simple bank transaction instantly over any(?) distance.

Quantum entanglement can and has been used to transmit information, however not faster than c.

[Cap'n Refsmmat]

Quantum entanglement can and has been used to transmit information, however not[/u'] faster than c.

This is not true, except in the case of quantum teleportation.

http://en.wikipedia.org/wiki/Quantum_entanglement

[doG]

Imagine a much simpler mechanism, a long crystalline pole, effectively incompressible. When you push one one end of the pole the whole thing moves. Now imagine there is a button at the other end of the pole that is operated when you push on the pole, i.e. you push on one end and simultaneously the button is operated at the other end. If this pole is 300km long how long will it take for the information to push the button be propagated from one end of the pole to the other since the button is effectively pushed at the time time that you input the energy to push it at the opposite end?

[5614]

Cap'n... yer I know, my bad!

 

doG firstly you cannot have a pole that is infinitely dense. Therefore it will compress. The reason for this is that the reason when you push one end of the pole the other moves is because the electron clouds surrounding the nucleus repel each other. This is an electrostatic force which is mediated by photons. It works at the speed of light.

 

Consequently your "push" travels through the rod at the speed of light. It is therefore not faster than light.

[doG]

Consequently your "push" travels through the rod at the speed of light.

So, you claim that it moves through the rod at the speed of light regardless of the material, huh? That sounds like a claim that we know all there is to know about any and all materials....