Faster than the speed of light

[Cosmos2001]

Well, I’m aware that the subject of Relativity is very complicated and non-intuitive; I will take time to get full understanding of all its nuances.
Recovering:

“No. Anything with no mass travels AT the speed of light. E.g. light.” – K^2
“Regardless, the photon moves at c and only c. Photons do not experience time.” – DaveC426913
“As I mentioned earlier, the individual photons still travel at c.” – Danger
“In medium, the actual photons still travel at the speed of light.” – K^2
“Nothing can locally travel faster than light” – Miguel Alcubierre

Presuming “nothing can move faster than light” is a true fact “fully supported by current and past experiments and observations”.

Hypothesis:
Having an array of dipoles, floating in the deep space, producing spaced-apart phase-shifted oscillations, generating strong/energetic “moving electrodynamic wave packet” along the array length, where the velocity of the “moving wave packet” is given by v=Lf (ref.: multiphase linear motors), where v is the velocity, L is the array length, and f is frequency.
If (f > c/L) then (v>c) and (∆v=v-c)

Keeping energy flow enough to keep acceleration (∆v/∆t):
E=½m(∆v)²

If “Nothing can move faster than light” then, applying enough energy flow, will (∆v=v-c) be converted effectively into acceleration contrary to direction of the “moving wave packet”? How much percent (0%-100%) is the chance of it being true?

 

[Dale]

Hypothesis:
Having an array of dipoles, floating in the deep space, producing spaced-apart phase-shifted oscillations, generating strong/energetic “moving electrodynamic wave packet” along the array length, where the velocity of the “moving wave packet” is given by v=Lf (ref.: multiphase linear motors), where v is the velocity, L is the array length, and f is frequency.
If (f > c/L) then (v>c) and (∆v=v-c)

Sure, nothing is wrong with this. In this case v is the phase velocity of the wave, which is not limited to c and does not violate SR in any way as no matter, energy, or information is traveling faster than c.

Keeping energy flow enough to keep acceleration (∆v/∆t):

What is being accelerated here? The phase velocity is not the velocity of any object and so it doesn't need any time to accelerate.

 

[Cosmos2001]

Sure, nothing is wrong with this. In this case v is the phase velocity of the wave, which is not limited to c and does not violate SR in any way as no matter, energy, or information is traveling faster than c.

What is being accelerated here? The phase velocity is not the velocity of any object and so it doesn't need any time to accelerate.

In an initial case, v is more the velocity of the “moving electrodynamic wave packet” that is being generated by the array of dipoles that is adjustable v=Lf (ref.: multiphase linear motors)

The array of dipoles is that which have mass and is to be accelerated. I was anticipating the overall energy requirement.

I think we can have two cases:

1. conventional “moving wave packet” propagating in the outer space having no matter, energy, or information traveling faster than c;
2. forced “moving electrodynamic wave packet” along the array length, receiving enough flow of energy for keeping (v>>c) , in this case, we can have strongly forced energy moving along the array length faster than c, but if the array of dipoles moves to the opposite direction, then the whole conjunct will have nothing faster than c.

Before the “moving wave packet” propagating away from the array of dipoles, will the extra energy be converted into acceleration propelling the array of dipoles to the opposite direction?

Obs: In this case, the array of dipoles is floating in the deep space. Another case is the array fixed inside a container in which net propagation of energy to dipoles would be blocked by stationary waves. I think if the array is floating in the deep space, without stationary waves surrounding it, it will have facilitated the propagation of energy to dipoles.

 

[Dale]

The array of dipoles is that which have mass and is to be accelerated. I was anticipating the overall energy requirement.

I thought the dipoles were just generating the wave with phase velocity v>c. If the dipoles are being accelerated then what is doing the accelerating? Your setup is not very clear.

In any case, dipoles work according to Maxwell's equations so you will never get a group velocity >c or any material object traveling with v>c.

 

[Phrak]

Infinity is not a number - that's why it is undefined.

It is defined in Infinitesimal Calculus.

...The infinitesimal calculus does a better job of making sense of Δy/Δx where Δx --> 0, than any other calculus of which I am aware.

 

[Phrak]

"Nothing travels at greater than the speed of light" is just street language. Ignore it.

There's plenty of stuff that locally propagates at great then c. In fact most stuff does have this greater-than-c attribute in various incarnations. What's the point of this, Cosmos; what is driving you?

I get the impression that you are dissatisfied with conventional wisdom in the claim that massive stuff must propagate at less than c. In fact, I think you take this as a challenge. This I like. Am I in error in any of this?

 

[Cosmos2001]

I thought the dipoles were just generating the wave with phase velocity v>c. If the dipoles are being accelerated then what is doing the accelerating? Your setup is not very clear.

In any case, dipoles work according to Maxwell's equations so you will never get a group velocity >c or any material object traveling with v>c.

I’m sorry; it is difficult to me to express it in a clearer form.
Now, I’m not trying to violate “nothing can move faster than light”; I’m trying to use it as support.

The energy in each dipole will never travel faster than c, but the overall energy moving along the array length will be forced (v>c), however, in the surrounding medium the speed is limited to c. To prevent speed violation; the array of dipoles will be forced to move to the opposite direction, doing (v=c), evicting energy flow faster than c.

If an object is traveling at low speed, vacuum doesn’t offer both support and resistance to change velocity. If the object is traveling close to c, it will offer resistance. The idea here is to take advantage of the resistance transforming it into support for initial acceleration of massive objects. Is it possible?

 

[epenguin]

I am surprised this thread reaches 4 pages without a mention of tachyons, particles with the remarkable properties: 1. Even I have heard of them 2. They can only travel faster than light - it takes infinite energy to slow them down to that speed. They achieve this remarkable property by their mass being an imaginary number.

Like all the most elite particles they are not actually known to exist. They seem to have been played with as an idea over the years. I suspect and would like to think this play is not entirely futile.

At the risk of being thought to have suffered an infantile regression, if they existed would we see them? Would they see us? Couldn't they exist in an incommunicado copresent parallel universe and mightn't they be worlds of positrons and antiprotons and this SOLVE THE PROBLEM OF BARYON NUMBER ASYMMETRY? Where do you get application forms for Nobel Prizes?:shy:

Anyway there is a Wikipedia article about them http://en.wikipedia.org/wiki/Tachyon - I found it quite difficult, but this one http://en.wikipedia.org/wiki/Tachyons_in_fiction was easier. It is based on the following fundamental principle: "it can impart a science-fictional "sound" even if the subject in question has no particular relation to superluminal travel (a form of technobabble, akin to positronic brain)."

 

[Dale]

The energy in each dipole will never travel faster than c, but the overall energy moving along the array length will be forced (v>c),

No, only the phase velocity will be >c. Energy does not move at the phase velocity.

however, in the surrounding medium the speed is limited to c. To prevent speed violation; the array of dipoles will be forced to move to the opposite direction, doing (v=c), evicting energy flow faster than c.

I don't know how you arrive at this conclusion. The array of dipoles won't move at all, dipole radiation is symmetric.

If an object is traveling at low speed, vacuum doesn’t offer both support and resistance to change velocity. If the object is traveling close to c, it will offer resistance. The idea here is to take advantage of the resistance transforming it into support for initial acceleration of massive objects. Is it possible?

Not even remotely. Lots of experiments have been done with phase velocities >c. The kind of propulsion you envision doesn't exist. There is no "traction" from phase velocities like you are supposing. In fact, there is no physical significance to phase velocities >c at all any more than there is a physical significance to the velocity of the "dot" from a laser pointer.

 

[Cosmos2001]

No, only the phase velocity will be >c. Energy does not move at the phase velocity.

I don't know how you arrive at this conclusion. The array of dipoles won't move at all, dipole radiation is symmetric.

Not even remotely. Lots of experiments have been done with phase velocities >c. The kind of propulsion you envision doesn't exist. There is no "traction" from phase velocities like you are supposing. In fact, there is no physical significance to phase velocities >c at all any more than there is a physical significance to the velocity of the "dot" from a laser pointer.

In a multiphasic linear motor, if (v<c), energy move at the phase velocity, it is hard to refute this; I think is a true fact for (v<c) because without this the linear motor would not work.
My hypothesis is, if (v>c), the energy will move forcedly at the phase velocity, facing relativistic resistance.

It is only a hypothesis.
Always seeing it as a multiphasic linear motor: if (v<c) then energy will flow along it in a non-forced way because it will not face relativistic resistance, energy will be dissipated into outgoing multiphasic waves increasing their amplitude. If (v>c) then energy will face relativistic resistance in order to be dissipated into the outgoing multiphasic waves, relativistic resistance will become a hypothetical relativistic support.

DaleSpam, I have no problem with you proving I’m wrong, if you can I’m grateful to you, but I felt I’m failing in describing my point of view.

Well, I know that “lots of experiments have been done with phase velocities >c”, but I’m not finding out one using an array of dipoles.
Please, could you give some clue to finding it?

 

[Dale]

In a multiphasic linear motor, if (v<c), energy move at the phase velocity, it is hard to refute this; I think is a true fact for (v<c) because without this the linear motor would not work.

An array of dipoles is not a multiphase linear motor. A linear motor needs a primary and a secondary, not just one of the two. The energy moves from the primary to the secondary at the speed of light, not at the phase velocity.

My hypothesis is, if (v>c), the energy will move forcedly at the phase velocity, facing relativistic resistance.

It is only a hypothesis.
Always seeing it as a multiphasic linear motor: if (v<c) then energy will flow along it in a non-forced way because it will not face relativistic resistance, energy will be dissipated into outgoing multiphasic waves increasing their amplitude. If (v>c) then energy will face relativistic resistance in order to be dissipated into the outgoing multiphasic waves, relativistic resistance will become a hypothetical relativistic support.

No. If v>c then you will just have an ineffective transfer of energy from the primary to the secondary. Most of the energy will just be radiated away or dissipated as heat.

DaleSpam, I have no problem with you proving I’m wrong, if you can I’m grateful to you, but I felt I’m failing in describing my point of view.

Well, I know that “lots of experiments have been done with phase velocities >c”, but I’m not finding out one using an array of dipoles.
Please, could you give some clue to finding it?

Just Google "phased array" and "phase velocity" to see what is there. I think you need to learn some basic EM concepts before worrying too much about the experimental details and relativistic effects. Specifically you should learn about motors and dipole antennas.

 

[Cosmos2001]

An array of dipoles is not a multiphase linear motor. A linear motor needs a primary and a secondary, not just one of the two. The energy moves from the primary to the secondary at the speed of light, not at the phase velocity.

No. If v>c then you will just have an ineffective transfer of energy from the primary to the secondary. Most of the energy will just be radiated away or dissipated as heat.

Just Google "phased array" and "phase velocity" to see what is there. I think you need to learn some basic EM concepts before worrying too much about the experimental details and relativistic effects. Specifically you should learn about motors and dipole antennas.

DaleSpam, frankly, you are impossible. I know an array of dipoles is not equal to a multiphase linear motor, but they are similar in some aspects. I know energy moves from the primary to the secondary at the speed of light, but the velocity of moving electric/magnetic fields can be adjustable (v=Lf).

I have failed completely in describing my point of view.
I’m giving up this topic.
You win!
Anyway, thank you for your suggestions; I will google them.

 

[Dale]

I know energy moves from the primary to the secondary at the speed of light, but the velocity of moving electric/magnetic fields can be adjustable (v=Lf).

The phase velocity of the fields is adjustable. No energy transfer occurs at the phase velocity.

I have failed completely in describing my point of view.

You have successfully described your belief that by making a wave with a phase velocity >c you will encounter some sort of relativistic resistance which will give your dipole array some support. It is wrong, but you have successfully described it.

 

[QuantumJG]

Is it possible to go faster than the speed of light? And why do some scientists say you can't?
Thanks -_-!

My knowledge of relativity is pretty basic. The fact is that you cannot go faster than c or 299,792,458m/s.

A cool phenomena is Cherenkov radiation. It is similar to a sonic boom but with light. A body of mass cannot travel at c, but when light travels in a medium other than a vacuum, it will travel at <c. A particle can now potentially travel faster than that light and it will emit radiation as a result. A cool example is the blue glow in reactors.

 

[MattRob]

Actually, you can fairly simply travel faster than 299,792,458 m/s from your own perspective due to time dilation as you approach the speed of light. However, from a stationary perspective, you will never see anyone else go at that speed.

Okay, I don't understand something. So Photons don't have any mass? How do they exert force when they hit an object, then. Isn't that something mass does? It seems more like photons have some, just an incredibly tiny amount of mass.

Also, don't photons travel faster than c? Okay, a light wave travels at c, but because it travels in a wave, it isn't traveling in a straight line. So if it were to travel in a straight line, it would go above c. I think I've read about an experiment to do with this somewhere, where the scientists ultimately decided that it does travel faster than c but doesn't carry any information. This is something I've never really understood. How is it that something can travel faster than c but truly not carry any information?...

So, in my imaginary lab, I've got this device that can send out these straight-path photons that don't carry any information but travel faster than c. At the other end of the lab, there's a special computer I've made. The computer will start "recording" when it receives 5 photons in a string, each 1 nanosecond apart. After that, every nanosecond, if it doesn't receive a photon, it will make a 0. If it does receive a photon, it makes a 1. And so my other device is made to emit the photons at 1 nanosecond intervals so that the 1s and 0s end up creating the data. Viola, the fact that it exists at all is information. So if anything can travel faster than c, then it carries information.

Two other things, Quantum entanglement and quantum tunneling. I can sort of understand that entanglement doesn't carry information because it's randomized. But randomization is really a fancy way of saying we don't know the factors. So if they could be discovered, or the randomization somehow controlled, then couldn't entangled particles transfer information FTL?

And now Quantum tunneling. I haven't heard any reason why it wouldn't work as FTL.

 

[Dale]

Actually, you can fairly simply travel faster than 299,792,458 m/s from your own perspective due to time dilation as you approach the speed of light.

Usually "your own perspective" means "in a reference frame where you are at rest", in which case your velocity is 0 by definition.

Okay, I don't understand something. So Photons don't have any mass? How do they exert force when they hit an object, then. Isn't that something mass does?

No, that is something momentum does. Photons have momentum.

Also, don't photons travel faster than c? Okay, a light wave travels at c, but because it travels in a wave, it isn't traveling in a straight line. So if it were to travel in a straight line, it would go above c.

I think you need to learn a bit more about Maxwell's equations. A light wave is not some piece of matter which undulates like a snake to go forward. It is an electromagnetic field which varies from place to place.

I think I've read about an experiment to do with this somewhere, where the scientists ultimately decided that it does travel faster than c but doesn't carry any information. This is something I've never really understood. How is it that something can travel faster than c but truly not carry any information?...

Can you cite the experiment in question?

 

[Cosmos2001]

No, that is something momentum does. Photons have momentum.

Photon can behave as either particle or wave.
It exerts a force when it hit an object, losing energy after that. Could it be because one of the wave half-cycle is mediating interaction between the interstellar medium and the object?

 

[Dale]

Could it be because one of the wave half-cycle is mediating interaction between the interstellar medium and the object?

I don't know what this means.

 

[DaveC426913]

I don't know what this means.

Cosmos plays pretty fast and loose with terms.

 

[Cosmos2001]

Cosmos plays pretty fast and loose with terms.

Photon doesn’t have any mass, but it has momentum.
Momentum is the product of the mass and velocity (p=mv)
It seems contradictory.
Is there an explanation for this, such as an interaction with something else?

 

[DaveC426913]

Photon doesn’t have any mass, but it has momentum.
Momentum is the product of the mass and velocity (p=mv)

That is the classical definition of momentum.

 

[Dale]

Photon doesn’t have any mass, but it has momentum.
Momentum is the product of the mass and velocity (p=mv)
It seems contradictory.
Is there an explanation for this, such as an interaction with something else?

Sure there is an explanation. That definition of momentum is only approximate and only applies for particles with v<<c.

In a more modern understanding momentum is the conserved quantity corresponding to spatial-translation symmetry. Thus a field can also have momentum provided that its Lagrangian is invariant wrt spatial translations. You should read up on Noether's theorem.

 

[MattRob]

Usually "your own perspective" means "in a reference frame where you are at rest", in which case your velocity is 0 by definition.

Look, I'll do it now mathematically. If observer is traveling at .9c, then he is traveling at 269,813,212 m/s.

Now to calculate time dilation using the Lorentz equation (Sorry, don't know how to use the fancy math fonts):
L = c / sqrt( c^2 - v^2 )

L = 299,792,458 / sqrt( 299,792,458^2 - 269,813,212^2 )
L = 299,792,458 / sqrt( 89,875,517,873,681,764 - 72,799,169,369,756,944 )
L = 299,792,458 / sqrt( 17,076,348,503,924,820 )
L = 299,792,458 / 130,676,503
L = ~2.294

For every 2.294 seconds of stationary observer time, 1 second of traveling observer time passes. Now, time dilation is accounted for the velocity of the observer, since speed is distance over time. I'll be using the reciprocal, since in this case time is passing at a slower rate for the traveler, while using the raw non-reciprocal would result in the opposite effect.
1/~2.294 = 0.43588989486853601900818999255813

269,813,212 meters / 1 second
Now, correcting for time dilation
269,813,212 meters / 0.43588989486853601900818999255813 second

618,993,959 meters / second

Much faster than 299,792,458 meters a second. From your own perspective, anyways. That is to say, a stationary object will fly by at 618,993,959 meters a second, and you will travel 4 Ly in 1.937 years.

No, that is something momentum does. Photons have momentum.

And momentum is proportional to mass. And yes, photons do have mass as a matter of fact. E=mc^2, the equation doesn't mean there's a relationship in-between mass and energy, it means mass is energy. "Is", being another word for "equal to".

I think you need to learn a bit more about Maxwell's equations. A light wave is not some piece of matter which undulates like a snake to go forward. It is an electromagnetic field which varies from place to place.

In it's spare time it will sometimes act like a particle, too. Just has a darned habit of not deciding which one to be.

Can you cite the experiment in question?

That's the darned thing about hearing something interesting somewhere, it's always heck trying to find it again. I think it was to do with early radar experiments, but I'll try to find this and come back to it.

 

[Oudeis Eimi]

And momentum is proportional to mass. And yes, photons do have mass as a matter of fact. E=mc^2, see the "="? It means "equals". The equation doesn't mean there's a relationship in-between mass and energy, it means mass is energy.

Most everything in the above paragraph is wrong.

 

[Dale]

Look, I'll do it now mathematically. If observer is traveling at .9c, then he is traveling at 269,813,212 m/s.

Now to calculate time dilation using the Lorentz equation (Sorry, don't know how to use the fancy math fonts):
L = c / sqrt( c^2 - v^2 )

Sure, but in what way is that the observer's own perspective? From the observer's own perspective he is at rest and his clocks are not time dilated.

And momentum is proportional to mass. And yes, photons do have mass as a matter of fact. E=mc^2, the equation doesn't mean there's a relationship in-between mass and energy, it means mass is energy. "Is", being another word for "equal to".

There are two distinct concepts of "mass" in special relativity. One is called "relativistic mass", that is the mass you are referring to, it is the "mass" that increases as a particle's speed increases. The other is called "invariant mass" or "rest mass", that is the mass that people are referring to when they say that a photon has no mass. In modern physics the unqualified term "mass" usually refers to "invariant mass" and when someone wants to refer to the relativistic mass they generally add the qualifier in order to avoid confusion. The use of relativistic mass is deprecated by most modern physicists.

 

[MattRob]

Sure, but in what way is that the observer's own perspective? From the observer's own perspective he is at rest and his clocks are not time dilated.

No, but by receiving a data stream and referencing it with his own information he can know that he is, in fact, not at rest, and that his clocks are dilated in reference to a stationary observer. (Or, at least the communications facility back on Earth.)

This is really somewhat besides the point though, I'm pretty sure I've made myself clear. It is in fact from his own perspective, as from a stationary observers' perspective, he is traveling at .9c, and not 618,993,959 m/s.

There are two distinct concepts of "mass" in special relativity. One is called "relativistic mass", that is the mass you are referring to, it is the "mass" that increases as a particle's speed increases. The other is called "invariant mass" or "rest mass", that is the mass that people are referring to when they say that a photon has no mass. In modern physics the unqualified term "mass" usually refers to "invariant mass" and when someone wants to refer to the relativistic mass they generally add the qualifier in order to avoid confusion. The use of relativistic mass is deprecated by most modern physicists.

Okay, I'll take that.

But the point of conversation is FTL travel, from a stationary observer's point of view, by finding some loophole in physics. So, to return to that point...

"Two other things, Quantum entanglement and quantum tunneling. I can sort of understand that entanglement doesn't carry information because it's randomized. But randomization is really a fancy way of saying we don't know the factors. So if they could be discovered, or the randomization somehow controlled, then couldn't entangled particles transfer information FTL?

And now Quantum tunneling. I haven't heard any reason why it wouldn't work as FTL."

 

[Dale]

he is, in fact, not at rest

What does this mean? Are you under the mistaken impression that whether or not something is moving has some sort of frame-independent meaning? If not, then what do you mean by "in fact"?

A person is at rest or moving relative to a given frame of reference. In the observer's own frame he is at rest and in any other frame he is moving. There is no coordinate independent sense in which he is "in fact" not at rest.

It is in fact from his own perspective, as from a stationary observers' perspective, he is traveling at .9c, and not 618,993,959 m/s.

He is at rest (0c) from his own perspective, by definition. He is traveling at .9c from someone else's perspective. There is no inertial frame in which he is traveling at any v>c.

randomization is really a fancy way of saying we don't know the factors. So if they could be discovered, or the randomization somehow controlled, then couldn't entangled particles transfer information FTL?

Yes, if the laws of physics that we are currently using turn out to be incorrect then it is certainly possible that they might be incorrect in such a way as to allow FTL communication. But then we would be talking about science fiction rather than science.

 

[John232]

Seems to me that the science fiction of FTL travel has already started because of cosmic background radiation showing that the universe expanded FTL. If galaxies can travel FTL with the expansion of space then any type of velocity addition done on them would be false because there is no limit of the rate of speed between them becuase a majority of their motion is defined by the expansion of space itself.

 

[MattRob]

He is at rest (0c) from his own perspective, by definition. He is traveling at .9c from someone else's perspective. There is no inertial frame in which he is traveling at any v>c.

No, but as he reaches .9c from a stationary viewpoint (stationary being an observer set on the surface of any planet, as the velocity of any nearby various body in their orbits is inconsequential relative to relativistic velocities), he will traverse 618,993,959 meters of distance in-between two stationary points every second.

I guess I was wrong to assume I was understood when I meant "at rest" to mean the velocity of any nearby common celestial bodies, the difference in-between which velocities is inconsequential in comparison to the observer's own velocity.

To get it in another time, if he is to leave Earth for Proxima Centauri, which is 4.4 Ly away, at .9c, he will arrive about 1.9 years later from his own perspective, for an average speed of 618,993,959 m/s, which is greater than the given value of c, 299,792,458 m/s. I did the math in my earlier post. However, because of this same time dilation, light will appear to move at 687,723,898.652 m/s, so though the observer strictly isn't going faster than light, he is going faster than 299,792,458 m/s.

Yes, if the laws of physics that we are currently using turn out to be incorrect then it is certainly possible that they might be incorrect in such a way as to allow FTL communication. But then we would be talking about science fiction rather than science.

I always thought the purpose of a hypothesis was to put established science to the test. Seeing as we've never achieved FTL before, at least not to my knowledge, an FTL thread is nothing but a hypothesis, which doesn't necessarily conflict existing science, as much as add to it.

With an attitude of, "if it's not something already established, it's science fiction", with an implied meaning that we can only use established facts, then no hypothesis could be made at all, and science would come to a screeching halt.

It's good to have imagination and come up with new ideas, that's the only way science can progress. The important thing is to test them adequately and correctly, not to not come up with them at all! Scientific advancement only comes through new, wild ideas, like the "strange" idea that the speed of light isn't additive to the velocity of the emitter!

EDIT: Heck, Isaac Newton's idea that gravity works by the inverse of the square was formulated then put away for years because he considered it too outlandish. We're only lucky enough to have discovered it because years later by an astounding coincidence a friend of his asked that exact question.

Anyways, not to assume that the current scientific understanding is wrong, but what is the current scientific understanding on the subject of quantum entanglement and it's use as FTL communication? Was I right that current understanding is that it can't carry information due to randomization?

Or, for that matter, I still have no response to Quantum tunneling as a method of FTL travel.

 

[John232]

We could only hope that science fiction writers do not come up with viable technology in their stories or it could lead to the biggest detourent to scientific progress.

 

[Dale]

I always thought the purpose of a hypothesis was to put established science to the test. ...

With an attitude of, "if it's not something already established, it's science fiction", with an implied meaning that we can only use established facts, then no hypothesis could be made at all, and science would come to a screeching halt.

You are not proposing a hypothesis, you are simply speculating. There is a huge difference. A hypothesis is a quantitative prediction about the measured outcome of a specific experiment. That is why what you were proposing was science fiction, not science.

It's good to have imagination and come up with new ideas, that's the only way science can progress. The important thing is to test them adequately and correctly, not to not come up with them at all!

Sure, and that is the purpose of scientific journals and scientific conferences. That is not the purpose of this site. This site is for learning mainstream physics, not for advancing the state of the art. Please review the rules on overly speculative posts which you agreed to when you signed up.

 

[MattRob]

Sure, and that is the purpose of scientific journals and scientific conferences. That is not the purpose of this site. This site is for learning mainstream physics, not for advancing the state of the art. Please review the rules on overly speculative posts which you agreed to when you signed up.

Wow. Nothing I've said so far is overly speculative. I'm only asking questions to the current state of science. Here's my current unanswered question:
"Anyways, not to assume that the current scientific understanding is wrong, but what is the current scientific understanding on the subject of quantum entanglement and it's use as FTL communication? Was I right that current understanding is that it can't carry information due to randomization?

Or, for that matter, I still have no response to Quantum tunneling as a method of FTL travel."

Breaking 299,792,458 m/s through time dilation is not overly speculative. It's current science. I'm asking the current state of science in regards to certain processes in their use of FTL travel, such as quantum entanglement and tunneling.
In current mainstream physics, is it possible to use Quantum entanglement and tunneling for FTL travel/communications?

 

[Dale]

Seems to me that the science fiction of FTL travel has already started because of cosmic background radiation showing that the universe expanded FTL. If galaxies can travel FTL with the expansion of space then any type of velocity addition done on them would be false because there is no limit of the rate of speed between them becuase a majority of their motion is defined by the expansion of space itself.

Don't take that too seriously. In curved spacetime the relative velocity of distant objects is mathematically ill-defined.

 

[Dale]

Nothing I've said so far is overly speculative.

You don't consider this overly speculative?:

But randomization is really a fancy way of saying we don't know the factors. So if they could be discovered, or the randomization somehow controlled, then couldn't entangled particles transfer information FTL?

I'm only asking questions to the current state of science

According to the current state of physics there are no tachyons yet discovered nor have any wormholes been discovered. In principle wormholes are not forbidden by GR, I don't know if tachyons are forbidden by the standard model.

 

[MattRob]

Not really, It was a way of asking what the problem is with entangled particles as FTL.

 

[Dale]

Entangled particles don't travel FTL and they don't transmit information FTL. What do you think is FTL about them?

To understand why they don't transmit information let's propose an entangled comm system and see what would happen. Observers A and B have a whole pile of entangled particles which are each entangled for their polarization state. A tries to send a message to B. First A measures a few hundred particles. B measures the entangled particles and gets a 50/50 random distribution. Then A doesn't measure the next few hundred. B measures the entangled particles and gets a 50/50 random distribution. Then A measures a subset of the next few hundred. B measures the entangled particles and gets a 50/50 random distribution.

Nothing that A does changes what B measures. When A and B later reunite they find that all of the particles that A measured are exactly anti-correlated with the particles that B measured, but B has no way of distinguishing the particles that A measured from the ones he didn't.

 

[darkhorror]

To get it in another time, if he is to leave Earth for Proxima Centauri, which is 4.4 Ly away, at .9c, he will arrive about 1.9 years later from his own perspective, for an average speed of 618,993,959 m/s, which is greater than the given value of c, 299,792,458 m/s. I did the math in my earlier post. However, because of this same time dilation, light will appear to move at 687,723,898.652 m/s, so though the observer strictly isn't going faster than light, he is going faster than 299,792,458 m/s.

Your just mixing and matching frames of reference. You use the time in the traveling frame of reference and the distance in the Earth's frame. This doesn't make any sense. How about answering these questions.

So how far did the ship travel?
How long did it take?

 

[DaveC426913]

However, because of this same time dilation, light will appear to move at 687,723,898.652 m/s

No, it will not. Light will still be measured to move at 300,000km/s.

What is true is that he will measure the distance to Centauri to be much shorter than he thought it was when he checked it on Earth.

 

[MattRob]

No, it will not. Light will still be measured to move at 300,000km/s.

What is true is that he will measure the distance to Centauri to be much shorter than he thought it was when he checked it on Earth.

Length contraction? I always thought the object accelerating experiences length contraction. So how does this work?

 

[Dale]

Length contraction? I always thought the object accelerating experiences length contraction. So how does this work?

The acceleration is not relevant, only the relative velocity and your velocity relative to yourself is always 0.

Nothing "experiences" length contraction, meaning that you never measure yourself to be length contracted. In your own frame you are never length contracted nor time dilated. It is always the moving clock or rod which is length contracted or time dilated in your frame.

 

[LBrandt]

You would never even expect to be length contracted or time-dilated in your own frame. How would that be possible? Even if you choose to consider this, what would be your standard of measurement? In your own frame, anything that you used to measure this would itself also be length contracted or time-dilated. As as example, if your own width were reduced to half its previous value, any ruler or measuring device would be reduced by the same factor. All values, including length and time are always normal in your own frame.

 

[MattRob]

That I understand. Except if you're contracted and you brought a ruler along, then wouldn't it make the rest of the universe seem to expand? Since because your ruler is shorter, it would take more copies of your ruler to reach from point A to point B, so wouldn't they seem farther apart instead of closer? That's what I meant.

Except now that you mention it, according to length contraction you should measure the distance in-between point A and point B to be contracted. But your own contracted length will make it seem just as much longer as it's contraction makes it seem shorter.

But, if you don't measure your own contraction at all not because of impossibility of measuring but because you don't actually contract from your own standpoint, and you contract from other viewpoints, then wouldn't you measure your own ship to be larger than a stationary observer would measure it? (Stationary being the velocity of adjacent celestial bodies),
i.e. your measurement says distance A is 2.2e50 shiplengths and a stationary observer sees distance A as being 6.6e50 shiplengths?

I'm sorry if the tone is coming off wrong, I'm not saying you're wrong, I'm just trying to understand how this works...

 

[LBrandt]

If you are in uniform motion relative to an observer, he will appear length contracted to you, and you will appear length contracted to him, but neither of you will consider yourselves to be length contracted.

 

[DaveC426913]

Your ruler, as with anything inside your spaceship, will be exactly as it has always been.

But the distance to Centauri will be dramatically shortened. Also, everything along your axis of movement will be flattened. i.e Centauri will appear as a flattish disc, rather than a sphere.

 

[MattRob]

So... Hypothetical question, then. Say there's a railroad crossing in North Carolina, and the train is somehow moving at relativistic speed along the rails. There's a car in N. Carolina about to cross the track. From the car's point of view, only going 25 mph, the train is contracted to a length of only a few feet, and is somewhere back in New Jersey, meaning the track ahead of them is clear and they can safely cross. (I know that's not far enough away, but for this point let's pretend New Jersey is a light-minute away).
However, from the train's point of view, because the distance from New Jersey to North Carolina is contracted, the front of the train is on the railroad crossing in N. Carolina when the car crosses.
But from the Car's point of view, because the train is contracted, the front of the train is somewhere in New Jersey.
So what happens to the car when it crosses?
From the train's point of view, it will smash into the train engine.
From the car's point of view, it will simply cross safely.

That's why I have such difficulty understanding length contraction as it is...

 

[Dale]

From what you describe here I think that your confusion is with the relativity of simultaneity, not length contraction.

 

[DaveC426913]

From what you describe here I think that your confusion is with the relativity of simultaneity, not length contraction.

Yeah, I started to describe why the length-contracted train was not still in New Jersey but realized my answer would only make it more confusing. I thought I'd leave it to someone who could be more eloquent and succinct.

MattRob, suffice to say, at least for now, that the front of the train is exactly where it is expected to be for the car river and the train engineer. So, car go boom.

The confusion comes when the car driver attempts to time when the caboose reaches the crossing. And timing events is where relativity gets tricky. You cannot assume that you simply "see" everything (such as the entire train). You must take into account distances and times when you examine properties about an object moving relative to you.

 

[vish_al210]

I don't think tha tlight travels but rather it propogates... by exchange of energy. If an object needs to move it needs to overcome a lot of factors, but if the light energy emitted by it or sound energy or heat energy emitted by it needs to propagate then it only needs to exchange the energy, but then the question is what about vacuum, well heat transfers through vacuum and so does light. but still it is transfer of energy... Hence they are much faster..
All equations, postulates and proofs are only extensions of what we can see, observe and understand. As we understand, observe, see more and more, equations change, exceptional cases are putforth and so on... so wait.. and the equations would change... someday when we understand and pick a different reference than C, things would change... equations would change, then that new reference would be the limit... remember at one point in time 'sky' was the limit...

 

[acarpenter]

the only thing that can travel at the speed of light, is something massless, eg a photon.

however what i fail to understand is that photons have a rest mass of zero. yet photons have to be in motion and cannon be at rest. photons not at rest have mass. so therefore how can a photon be traveling at the speed of light when surely it cannot be Massless??

 

[Dale]

It sounds like you may be confused by the various definitions of mass:
invariant mass: sqrt(E²/c⁴ - p²/c²)
rest mass: a less precise name for invariant mass
relativistic mass: E/c²