Speed of electricity

[RQ]

Electricity, after reaching its final point moves at an infinite (seemingly) speed if it's in a cable and it can be stored with 100% accuracy if there are no cut cables.

Split from: 4D existence by BobXP

[Keiji]

Electrons don't move infinitely fast.

[RQ]

Electrons don't, but electricity in a cable does.

Each electron pushes the next, so whether it is the electron that was pushing or the one that came out, it doesn't matter, so there you go infinity described by finite..ness.

This is why when you are talking to someone across the country, you don't talk, and then hear a pause, you talk and there's an immediate response Bob.

[Keiji]

This is why when you are talking to someone across the country, you don't talk, and then hear a pause, you talk and there's an immediate response Bob.

Electricity does NOT travel instantly! If it did, they would bump into each other infinite times in zero seconds, so if you were to switch a light on the whole wire would burn up, for instance, because of friction. Think before you post.

It does, however, travel very fast. Which is why "when you are talking to someone across the country, you don't talk, and then hear a pause, you talk and there's an immediate response".

[RQ]

It travels infinitely fast, because each electron can be traded for another one if it's all on the same frequency. Imagine this. There is a tube with balls, if I push one ball through the tube with balls towards you, your gonna see a ball coming towards you INSTANTANEOUSLY INFINITELY FAST, although it's not the same ball it's the same idea with the electrons, get it now, it's practically infinitely fast BOB.

[Keiji]

NO! That is not a proper analogy. ELECTRONS DO NOT OCCUPY MAXIMAL SPACE INSIDE METALS. THEY HAVE GAPS BETWEEN THEN AND HENCE DO NOT AFFECT THE OTHER END OF THE METAL INSTANTLY.

[pat]

Correct, bobxp. And, even if there were no gaps, the fastest the signal can possibly travel is the speed of light. Relativity says that the fastest that information can travel (barring quantum-entanglement scenarios that still puzzle people) is light speed.

[Keiji]

And, even if there were no gaps, the fastest the signal can possibly travel is the speed of light.

I disagree with that. Imagine a very long pole suspended in space, hundreds of miles long. If someone pushes one end of the pole, the other end moves instantly, right? Now, imagine a tube hundreds of miles long in space, with the whole tube filled with marbles the radius of the inside of the tube. If someone were to push the marble at one end, the marble at the other end would come out instantly, wouldn't it?

[pat]

I am not sure what relativity has to say about that sort of case. But, you're supposing that the impulse can move arbitrarily fast or that the rod is arbitrarily rigid. I'm sure that neither is the case in reality... but I'm not sure how the theory goes....

[Keiji]

Since each marble forces the one in front of it to move, then theoretically each one should move at exactly the same time.

[jinydu]

I'm quite sure its the second assumption that is incorrect. Rigid bodies (push one end, the other end moves instantaneously) are not allowed in Special Relativity. Any such body would allow instantaneous communication.

[RQ]

Yes they do, electrons are right next to each other in an electrical pulse, and yes when you push something that pushes something else is pushes it instanteneously fast, whether or not it's the same electron, it moves instantaneously fast because in electricity they move along the metal in a cable one behind the other. It violates no law, and it's technically not faster than light, but practically it is infinite speed, and that's why bobxp when you talk to someone from LA to New York there is 0 pause.

[Keiji]

Yes they do, electrons are right next to each other in an electrical pulse

THEY DO NOT. GO READ A BOOK ON ELECTRICITY NOW.

[jinydu]

yes when you push something that pushes something else is pushes it instanteneously fast

That is exactly what a rigid body is. If you push one side of it, the push reaches the other side instantaneously. As mentioned previously, Special Relativity forbids faster than light communication. Your claim that electrical pulses move instataneously would allow instantaneously (which is obviously much faster than light speed) communication, since electrical pulses can be used as a form of communication. To see why instantaneous communication creates problems, think about the following situation:

Think of two spaceships in space, moving relatively to one another. At some particular time, the ships are very close together (so that the time it takes to send a light pulse from one ship to another is negligible). There's nothing in Special Relativity that places any limit to how close they can get. Taking advantage of this situation, both ships decide to synchronise their clocks. For simplicity, let's say they both set their clocks to 0 at the moment when they are very close to each other. Since they are both (to as good a degree of approximation as you wish) at the same place at the same time, Special Relativity assures us that there will be no problem with this. No problems so far.

But the ships are moving relative to each other, so they won't stay close for long. We can look at the situation from Ship A's frame of reference. From that point of view, Ship A is stationary, while Ship B is moving. Thus, according to the Time Dilation formula, Ship A will claim that its clocks are running normally, while Ship B's clocks should be running slower than normal. Similarly, Ship B will claim that its clocks are running normally, while Ship A's clocks should be running slower than normal. Still no problem here.

Now, let's introduce your proposal for instantaneous communication. Let's say that Ship A and Ship B are connected by a (very long) electric wire. Some time after the ships passed very close to each other, Ship A wants to know what time it is on Ship B's clock. Using the electric wire, Ship A sends a message saying "What time is it on your clock?" Since you claim that the pulse moves infinitely fast, the message arrives at Ship B's clock instantaneously. Also, because of the instantaneous communication, Ship B's reply arrives instantaneously. Just as that person on Ship A sends the message, one of his crewmates checks the clock on Ship A. Then, he compares the that with the reply from Ship B. Then, he sends another message to Ship B, telling them which clock is faster (or equivalently, which clock reading has the higher value. If clock A reads 10 minutes, while clock B reads 7 minutes, then clock A is running faster). Let's say t(A) = The reading on Ship A, while t(B) = The reading on Ship B.
All this happens in an arbitrarily small amount of time, since the communication is instantaneous.

But now, we come to a problem. Remember that according to Special Relativity, Ship A will say that its clock is running normally, while Ship B's clock is running slowly. Thus, according to the people on Ship A, what should happen is t(A) > t(B). However, Ship B will say that its clock is running normally, while Ship A's clock is running slowly. Thus, according to the people on Ship B, what should happen is t(B) > t(A). We have a contradiction. One measurement cannot be greater than and less than another measurement. If it turns out that t(A) > t(B), people on Ship B will complain that the laws of physics have been violated. If instead t(B) > t(A), people on Ship A will complain that the laws of physics have been violated.

It turns out that this problem can be fixed if instantaneous communication is impossible. There must be some time delay in communications. If you work this situation out mathematically, using the equations of Special Relativity, you will find that there is no problem only if you assume that the fastest possible speed of communication is the speed of light.

As for communicating between LA and New York, the reason that you notice no delay is that the distance is so short. Remember, the speed of light is very fast. Thus, even when talking with someone on the other side of the world, the time delay is less than 0.05 seconds (you can try calculating for yourself. Time delay = Diameter of the Earth/Speed of light). This is too small for you to notice.

[RQ]

First of all Ship A won't claim anything against ship B if they are moving at the same speed, but I understand your point and point taken, yes there are gaps between the electrons as bobxp said, and the pauli exclusion principle disallows for particles to be very near each other, but nonetheless electricity in cables when running continuously, goes much faster than 123 meters/second.

However if we had a tube with actual balls, say 5, when you push a 6th ball through the tube, the relative speed of the balls is instantaneously fast, and there is no pauli exclusion principle in this, thus information can be passed infinitely fast if the balls are identical, and you are trying to see what the ball looked like.

Now the information you are talking about is a particle getting from one place to the other, that same particle, and none other because that's the particle that observably occupied that region in space at that interval in time.

[jinydu]

Actually, my previous post shows that any instantaneous communication is impossible, no matter how many particles it uses.

Your example of balls in a tube would still lead to the contradiction in my previous post. Ship A and Ship B could still use the tube to communicate instantaneously. According to what you claim, if someone on Ship A pushes on a ball at his end, the ball at Ship B's end will feel the push immediately, and vice versa. The crew on each ship could install something to keep the balls from falling out, allowing multiple messages to be sent. They could also install a sensor at each end, to detect the vibrations of the ball. Now all they need is a code, so the other side can decode the vibrations of the ball at their end. The Morse Code would do nicely (three short "ball pulses" is one letter, three long ball pulses is another letter, and so on). Using this form of communication, they could then bring about the contradiction. This problem doesn't arise in real life because balls are made of protons, neutrons and electrons, which are governed by the exclusion principle.

Thus, by information communication, I mean something broader than just moving one particle from one place to another, since there are other means of communication. Actually, I mean anything that can be theoretically used to send a message.

However, there are some things that can travel faster than light. It is possible, so long as either 1) There is no way communication can take place or 2) The overall speed of information transfer is not faster than light. Here is one example:

Shine a flashlight on Pluto (the planet). Wave your finger in front of the flashlight. The shadow your finger casts on Pluto should move faster than the speed of light (if not, just shine the flashlight on a planet in another solar system). You may think this provides a means for faster than light communication, since you could clearly communicate a message just by varying the shape of the shadow, if you've agreed on a code before-hand. However, closer examination shows that the communication is in fact slower than the speed of light. This is because it takes time for the light (or lack of light, which is a shadow) to move from the flashlight to Pluto.

[Keiji]

The Morse Code would do nicely (three short "ball pulses" is one letter, three long ball pulses is another letter, and so on).

No, it would be better to use ASCII, and sample at a certain rate. Of course, the problem is that time dilation would change the sampling rates.

[jinydu]

In any case, the main point is that instantaneous communication would be possible if instantaneous were possible. Since instantaneous communication is impossible, therefore instantaneous ball pulses are impossible.

[Geosphere]

Maybe not as impossible as we think:
http://news.bbc.co.uk/2/hi/science/nature/3576594.stm

[PWrong]

Forgetting about relativity for a moment, forces don't transmit instantaneously.

1. When you push something, the force acting is actually a kind of electromagnetism. Electromagnetism, like all forces, is not instantaneous.

2. The balls can't be infinitely close together. When you push the first ball, it has to move foward slightly before it can impose a force on the next ball. The same applies to the molecules inside the balls.

3. Even if we assume that the balls are infinitely close together, they must have some degree of elasticity. Even if made of steel, each ball will be compressed by the force, which takes time.

However, there are some things that can travel faster than light. It is possible, so long as either 1) There is no way communication can take place or 2) The overall speed of information transfer is not faster than light.

That's no longer entirely true. A team of quantum physicists in Singapore developed a system just this year that allows money to be transferred faster than light by quantum entanglement. Ironically, the mayor used the technology to send them more funding. Unfortunately, I can't find this article on the net, but there are a few others about quantum entanglement around.

I have no idea what happens if you quantum-teleport information across spaceships.

[jinydu]

Well, ok. Instantaneous communication is impossible according to Special Relativity. Einstein dismissed the idea as "spooky action at a distance".

The conflict between using quantum entanglement for instantaneous communication and special relativity is still a hot area of debate right now. If we accept that instantaneous communication is possible, then one of the two postulates of special relativity is wrong. Thus, either the speed of light is not always constant (which means we can throw away all of the equations of special relativity) or not all non-acceleration frames of reference are equally valid (there is a universal frame of reference that can decide whether Ship A or Ship B is moving). Both of these possibilities are highly distasteful to most physicists (and myself).

As a point of consolation, some physicists believe they can fix the problem. For more information (and another demonstration of why instantaneous communication has problems with special relativity), see http://fergusmurray.members.beeb.net/Causality.html .

Edit by BobXP: Fixed your link.

[RQ]

The idea with balls is not communication, and yes electrons are at less than the speed of light, but certainly faster than 123 meters/second because of this, that is what I meant.

Shadow is the absence of light, which is not really "something" that travels faster than light even if it did, and that still wouldn't be instantaneous communication, but communication at the speed of light.
Gravity was thought to have infinite reach, yet recent data says it doesn't
The only true information, or so to speak, is the increase of the volume of the universe which increases about 5-10% every year or something like that. Hawking says that this might travel faster than light, but that obviously cannot be true, since galaxies are in a fixed state on their spot or in fixed movement around a spot, meaning if the universe expands, they will not be left behind, but rather expand with it, and since galaxies are made up of matter, they cannot travel faster than light, so Hawking was wrong.

By the way Chronicles of Riddick is a very good science fiction movie, and in it is a perfect example of time dilation (The guys in the Helign empire say that a comet precedes the World Destroyers, which is actually them warping through space at near the speed of light, and since time dilation it takes them thousands of years to reach the people of Helion, while it takes the World Destroyers several hours or so.)

[SavageBarnes]

Imagine a very long pole suspended in space, hundreds of miles long. If someone pushes one end of the pole, the other end moves instantly, right?

Wrong. Say you have a pole that is ten seconds long (it's length is the distance light travels in ten seconds). If you start revolving one end of the pole, the other end will respond ten seconds later.

[Keiji]

But, that is only because you SEE it happening 10 seconds later.

[jinydu]

Well, there's no way the other end can move instantly, if Special Relativity is right; because it could be used as a means of communication.

In fact, the push will take time to move along the pole because the pole is not a rigid body. In fact, if you look at the pole using a VERY powerful microscope, you would see that it is mostly empty space, with some atoms here and there. It takes time for an atom to transmit the force from the push to the next atom. On the atomic scale, the force is in fact electromagnetic, and I learned in Physics class that electromagnetic forces are transmitted by photons, which of course travel at the speed of light.

[RQ]

an atom pushing an atom is the same as two balls pushed by a hand through the tube. If there is no instantaneous communication there, then how do black holes get crushed to a point? That is infinitely small, and since there is communication after a black hole explodes and the particles are tracable back to their original sources, then isn't that an example of infinite communication.

[knigitz]

You guys are forgetting a key part in this whole tube of balls theory.

If you had a tube two lightyears long, and push a ball from one end the ball on the other end will move instantly, but the amount of kinetic energy needed would be extreme. Infinite kinetic energy? No sir, just enough to move whatever mass is in between the origin and the destination. The balls themselves would not move at a faster than speed light, but the kinetic energy would travel that far.

This does not disprove faster than light travel is not possible, as nothing traveled faster than light. The kinetic energy traveled from each ball seperately, not from one end to the other. Also, the balls themselves moved at such a small distance and speed.

However, the ball on the other end, if viewed by a telescope, would seem to move two years later. As that is the amount of time it would take for the light to hit off that end of the tube and come back to you. This however, is perception and not reality.

Just because light can only travel so fast, does not limit other things from getting to the destination faster. I have never believed in the "you cannot go faster than light" theory, and I never will. Afterall, what's one more kick right before you reach the barrier? It would take an extreme amount of energy to travel that fast, and a very strong ship. But I believe it's possible.

[jinydu]

If you claim that it is possible to send messages faster than the speed of light, how do you explain the problem raised by my post here?

That is exactly what a rigid body is. If you push one side of it, the push reaches the other side instantaneously. As mentioned previously, Special Relativity forbids faster than light communication. Your claim that electrical pulses move instataneously would allow instantaneously (which is obviously much faster than light speed) communication, since electrical pulses can be used as a form of communication. To see why instantaneous communication creates problems, think about the following situation:

Think of two spaceships in space, moving relatively to one another. At some particular time, the ships are very close together (so that the time it takes to send a light pulse from one ship to another is negligible). There's nothing in Special Relativity that places any limit to how close they can get. Taking advantage of this situation, both ships decide to synchronise their clocks. For simplicity, let's say they both set their clocks to 0 at the moment when they are very close to each other. Since they are both (to as good a degree of approximation as you wish) at the same place at the same time, Special Relativity assures us that there will be no problem with this. No problems so far.

But the ships are moving relative to each other, so they won't stay close for long. We can look at the situation from Ship A's frame of reference. From that point of view, Ship A is stationary, while Ship B is moving. Thus, according to the Time Dilation formula, Ship A will claim that its clocks are running normally, while Ship B's clocks should be running slower than normal. Similarly, Ship B will claim that its clocks are running normally, while Ship A's clocks should be running slower than normal. Still no problem here.

Now, let's introduce your proposal for instantaneous communication. Let's say that Ship A and Ship B are connected by a (very long) electric wire. Some time after the ships passed very close to each other, Ship A wants to know what time it is on Ship B's clock. Using the electric wire, Ship A sends a message saying "What time is it on your clock?" Since you claim that the pulse moves infinitely fast, the message arrives at Ship B's clock instantaneously. Also, because of the instantaneous communication, Ship B's reply arrives instantaneously. Just as that person on Ship A sends the message, one of his crewmates checks the clock on Ship A. Then, he compares the that with the reply from Ship B. Then, he sends another message to Ship B, telling them which clock is faster (or equivalently, which clock reading has the higher value. If clock A reads 10 minutes, while clock B reads 7 minutes, then clock A is running faster). Let's say t(A) = The reading on Ship A, while t(B) = The reading on Ship B.
All this happens in an arbitrarily small amount of time, since the communication is instantaneous.

But now, we come to a problem. Remember that according to Special Relativity, Ship A will say that its clock is running normally, while Ship B's clock is running slowly. Thus, according to the people on Ship A, what should happen is t(A) > t(B). However, Ship B will say that its clock is running normally, while Ship A's clock is running slowly. Thus, according to the people on Ship B, what should happen is t(B) > t(A). We have a contradiction. One measurement cannot be greater than and less than another measurement. If it turns out that t(A) > t(B), people on Ship B will complain that the laws of physics have been violated. If instead t(B) > t(A), people on Ship A will complain that the laws of physics have been violated.

It turns out that this problem can be fixed if instantaneous communication is impossible. There must be some time delay in communications. If you work this situation out mathematically, using the equations of Special Relativity, you will find that there is no problem only if you assume that the fastest possible speed of communication is the speed of light.

As for communicating between LA and New York, the reason that you notice no delay is that the distance is so short. Remember, the speed of light is very fast. Thus, even when talking with someone on the other side of the world, the time delay is less than 0.05 seconds (you can try calculating for yourself. Time delay = Diameter of the Earth/Speed of light). This is too small for you to notice.

Furthermore, why should the force from the push travel through a ball in zero time? In effect, you are assuming that the ball is a rigid body: Push one end, the other end moves instantly. What justifies this assumption?

[sup2069]

And, even if there were no gaps, the fastest the signal can possibly travel is the speed of light.

I disagree with that...imagine a tube hundreds of miles long in space, with the whole tube filled with marbles the radius of the inside of the tube. If someone were to push the marble at one end, the marble at the other end would come out instantly, wouldn't it?

No, that person would require infinite energy to accelerate the marbles to infinite speed.


Correct me if im wrong

[jinydu]

No, bobxp is not talking about accelerating the marbles to infinite speed. He's talking about sending a pulse through the marbles at infinite speed. In other words, you push the first marble, the first marble pushes the second marble, the second marble pushes the third marble, etc. Bobxp is claiming that the overall speed of the pulse is infinite.

However, I think that is impossible because marbles are not rigid bodies (see previous posts), and Special Relativity forbids instantaneous communication between distant places (see my previous post).