Are there particle's or masses that travel faster than light?

[falloutcast]

if it were possible to send a message or travel at speed's higher than light what would happen? i know that at the speed of light time would stop.but beyond...?

 

[Hans Dorn]

Messages already have been sent faster than light speed, by making use of the tunnel effect.

 

[ZapperZ]

Messages already have been sent faster than light speed, by making use of the tunnel effect.

This is not correct. There is still NO consensus that a tunneling signal travels faster than c. Please see:

H. Winful, PRL v.90, p.023901 (2003)
M. Buttiker and S. Washburn, Nature v.422, p.271 (2003)
H. Winful, Phys. Rep. v.436, p.1 (2006).

Zz.

 

[Shomy]

Messages already have been sent faster than light speed, by making use of the tunnel effect.

I thought that sending information faster than the speed of light was forbidden by special relativity

EDIT: But Tachyons (see http://en.wikipedia.org/wiki/Tachyons) can go faster than the speed of light, though they are highly hypothetical and controversial.

 

[falloutcast]

would there be consequences if faster than light were possible?

 

[Friesiangirl]

Don't the quantum computers send energy quicker than the speed of light via electron tunneling? I'm not sure if that counts as traveling.

Hayley

 

[falloutcast]

i found this on wiki,if you scroll down to "faster than light?". http://en.wikipedia.org/wiki/Propagator

 

[ZapperZ]

Please try not to use Wikipedia as a source, especially when you don't know the validity of the information that you are citing.

Zz.

 

[falloutcast]

i was asking if that article is reliable.

 

[Hans Dorn]

I'm a physics layman, so please bear with me...

I was under the impression that when a photon is created, it's wave function instantly fills the entire universe, i.e. there is a very small, but non-zero possibility of detecting it virtually anywhere.

Is this correct?

 

[falloutcast]

ok,i was watching a video if something were to exceed light speed,it would go back in time?!

 

[falloutcast]

Please try not to use Wikipedia as a source, especially when you don't know the validity of the information that you are citing.

Zz.

i read that a particle that is virtual is able to exceed light speed?

 

[Vanadium 50]

Falloutcast, we're trying to tell you that particles don't exceed the speed of light. So "what would happen if it could?" is like asking "if you could go north of the north pole what would be there?"

 

[ZapperZ]

I'm a physics layman, so please bear with me...

I was under the impression that when a photon is created, it's wave function instantly fills the entire universe, i.e. there is a very small, but non-zero possibility of detecting it virtually anywhere.

Is this correct?

This is a completely different subject and should not be discussed in this thread. You are asking about non-locality, where a particle's position is spread out over various locations. This is NOT the same as having a FTL movement! That is why I said this is a different subject.

Zz.

 

[ZapperZ]

There is ONE easy thing that we can do to settle this thread, and that is:

point out one verified and agreed-upon experiment in which a FTL message has been sent.

Don't use (i) tunneling signal, because of what I've mentioned above; don't use (ii) the NEC type experiment using anomalous dispersive media, because we had discussed this a gazillion times on here on why no part of that wave is moving faster than c; and (iii) don't use quantum entanglement, as in the Bell-type experiment, because one needs to look at the Quantum physics forum to figure out why it can't be done.

If we can't do this, then the OP has been answered, no?

Zz.

 

[Hans Dorn]

This is a completely different subject and should not be discussed in this thread. You are asking about non-locality, where a particle's position is spread out over various locations. This is NOT the same as having a FTL movement!
Zz.

Nonlocality leads to the possibility of FTL communication, though:

When you modulate a photon source with your message at location a, it is possible to pick up a strongly attenuated form of this signal at location b via the photon's wave functions.

If the creation of the wave function is instantaneous, then this type of communication is instantaneous, too.

Hence my question.

This is NOT the same as FTL movement.

This is OT w.r.t the thread title, but not w.r.t. the first post...

 

[JamesUniverse]

Yeah there have a particle that travel faster than a light which is ka-ki-yon I don't know if I spell it right or not, but I think not, but anyway this particle can not travel in a speed that lower than light year it can only travel in a speed that faster than light year. But this is just a theory can not be improve yet, but now scientists try figure it out right now.

 

[ZapperZ]

Nonlocality leads to the possibility of FTL communication, though:

But it doesn't lead to faster than light TRAVEL (as in the OP's question), because nothing is traveling.

Zz.

 

[ZapperZ]

Yeah there have a particle that travel faster than a light which is ka-ki-yon I don't know if I spell it right or not, but I think not, but anyway this particle can not travel in a speed that lower than light year it can only travel in a speed that faster than light year. But this is just a theory can not be improve yet, but now scientists try figure it out right now.

It's "tachyon", and this is hypothetical. If we want to deal with speculative, unverified particle, I can spew out several. Is this what we want, or do we want something that's verified, as per my question?

Zz.

 

[sanman]

Okay, so what about these vacuum fluctuations, which are said to be occurring at the sub-Planck scale. If we apply sub-Planck even to the time-axis, then doesn't this imply events which are occurring faster than light?

 

[03myersd]

If we take a photon and split it so that the two are entangled, then no matter what we do to one happens to the other INSTANTLY.

So you may think: "Hey I can send messages faster than light using this method."

But you can't. Think back to the whole wave particle duality thing. Its a wave until it is observed. Its the same with this basically. They appear to do it instantly as long as they are BOTH observed. But the only way we can do this is using traditional slower than light methods. Because of this communication using entangled photons or other faster than light methods are impossible, as they need slower than light methods to basically make them work.

 

[falloutcast]

can't a virtual particle's travel faster than light? or some connection between virtual particle's and and the idea of faster than light.

 

[WarPhalange]

Okay, so what about these vacuum fluctuations, which are said to be occurring at the sub-Planck scale. If we apply sub-Planck even to the time-axis, then doesn't this imply events which are occurring faster than light?

What does that even mean? What does "occurring faster than light" mean? I can flip 3 pancakes a minute, and that's faster than light can flip pancakes, but that's not what we care about, is it?

These supposed vacuum fluctuations create a particle-antiparticle pair. Light doesn't play a role in that. And they have to annihilate within a Planck second. Light doesn't play a roll in that, either.

 

[WarPhalange]

can't a virtual particle's travel faster than light? or some connection between virtual particle's and and the idea of faster than light.

No.

Virtual particles pretty much describe fields. Say you have a magnetic field. There is no particle per say that describes magnetic fields alone. But if say an electron went perpendicular into that field, it would have to start changing direction via F = qv x B, right? Well then you say virtual photons interacted with the electron.

 

[Hans Dorn]

If we take a photon and split it so that the two are entangled, then no matter what we do to one happens to the other INSTANTLY.

So you may think: "Hey I can send messages faster than light using this method."

But you can't.

I can't help but find this fact to be quite unfair :)

I fail to see why the double slit experiment with entangled photons can't be used as a communication device.

The setup is like this: One half (photon A) of a photon pair with entagled momentum is sent through a double slit and then detected (by detector A), while the other half (photon B) is captured by another detector (B).

Since detector B is able to determine his photon's momentum, and hence the momentum of the entangled photon A, detector A doesn't see an interference pattern.

This changes when you put a lens in the right place front of detector B that "maps" all B photons to the same spot, and makes their momentum indistinguishable.

With the lens in place, the pair's momentum is undecided, and detector A sees an interference pattern.

This setup seems to be able to transmit FTL messages. You have 2 easily distinguishable signals at detector A (absence/presence of interference) and can send these signals by placing/removing the lens at point B.

Can you give me some pointers to why this can't work?

 

[falloutcast]

is something traveling faster than light equivalent to something "going back in time"?

 

[Friesiangirl]

is something traveling faster than light equivalent to something "going back in time"?

I don't think so. I may be incorrect.

 

[pallidin]

I can't help but find this fact to be quite unfair :)

I fail to see why the double slit experiment with entangled photons can't be used as a communication device.

The setup is like this: One half (photon A) of a photon pair with entagled momentum is sent through a double slit and then detected (by detector A), while the other half (photon B) is captured by another detector (B).

Since detector B is able to determine his photon's momentum, and hence the momentum of the entangled photon A, detector A doesn't see an interference pattern.

This changes when you put a lens in the right place front of detector B that "maps" all B photons to the same spot, and makes their momentum indistinguishable.

With the lens in place, the pair's momentum is undecided, and detector A sees an interference pattern.

This setup seems to be able to transmit FTL messages. You have 2 easily distinguishable signals at detector A (absence/presence of interference) and can send these signals by placing/removing the lens at point B.

Can you give me some pointers to why this can't work?

I wonder if a "delayed choice quantum eraser" might shed some light on this. For example consider this text:

A delayed choice quantum eraser is a cross between a quantum eraser experiment and Wheeler's delayed choice experiment. This experiment has actually been performed and published by Yoon-Ho Kim, R. Yu, S.P. Kulik, Y.H. Shih, and Marlan O. Scully[1] This experiment was designed to investigate some very peculiar consequences of the well known double slit experiment in quantum mechanics, as well as the consequences of quantum entanglement. As this experiment is a more complex version of the quantum eraser experiment, study of that article may make this article easier to understand.

Source: http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser

 

[Cthugha]

The setup is like this: One half (photon A) of a photon pair with entagled momentum is sent through a double slit and then detected (by detector A), while the other half (photon B) is captured by another detector (B).

Since detector B is able to determine his photon's momentum, and hence the momentum of the entangled photon A, detector A doesn't see an interference pattern.

This changes when you put a lens in the right place front of detector B that "maps" all B photons to the same spot, and makes their momentum indistinguishable.

With the lens in place, the pair's momentum is undecided, and detector A sees an interference pattern.

This setup seems to be able to transmit FTL messages. You have 2 easily distinguishable signals at detector A (absence/presence of interference) and can send these signals by placing/removing the lens at point B.

Can you give me some pointers to why this can't work?

This is a common misunderstanding about these kind of double slit experiments.

In the double slit scenario you have to distinguish between two kinds of interference. There is the usual interference for single photons and there is two-photon interference, which is more accurately described as the interference of two probability amplitudes leading to one certain event.

Basically each of the two entangled photons behaves like thermal light, which means it has a rather short coherence time and volume. To see an interference pattern, you need the two slits to be positioned rather far from the photon source as this means, that you choose a smaller part of the photon source, which increases coherence.

For two-photon interference, you need to position the source nearer to the slit as this means that you will have a larger collection of pairs of k-values. You will see a larger part of the interference pattern if you include a larger range of k-values. The two-photon interference however, is only visible in coincidence counting, so you need to compare the results from both detectors, which makes ftl communication impossible, because you are not able to get the information from detector A to detector B faster than the speed of light.

Zeilinger has shown (see for example the Dopfer thesis - there is some other paper as well, but I do not know where it was published so I need to check) that these two kinds of interference forbid each other. The closest distance from the source to the double slit, which allows 100% visibility of the two photon interference pattern is already shorter than the minimal distance, which allows single photon interference. So if you see an interference pattern without looking at the entangled partner, the entangled partner does not matter anyway.

 

[03myersd]

Since detector B is able to determine his photon's momentum, and hence the momentum of the entangled photon A, detector A doesn't see an interference pattern.

The problem here is that by measuring the photons momentum, you then in fact change it.