Twice of the speed of light???

[Whiteaht]

Hi I have a couple of questions about this topic :

 

If gravity is the atraction of matter to other matter then what is gravitational lensing(light appantly not being matter) ???

 

Shouldn't all particals be matter??

 

If time slows the faster you move then do hot objects exprence time slower then cold objects?

[paultrr]

What legislation requires me to "prove it" ?? did some judge issue a "show cause" order or somethin'?

 

When an experiment is performed there are checks done to show weither something has transpired or not. Even with say quantum computers one requires error checking which is even done on normal computers. The path used to check for error is a C limited one. One could in theory send some information like spin change via entanglement and just assume the message was transfered. But without checking that such has taken place there is no way to really show such has. Its not a law in the classical sence. Just a requirement of establishing an event actually took place or that certain information was actually transfered correctly. For this type of error checking one is limited to sending the information used to check for error via C limited means and verifying such by C limited means. The end result is that due to this real information always remains C limited.

 

There has been some tests conducted to see wither one could beat C as far as information transfer goes using entanglement. While changes in one entangled particle to another do seem to transfer far faster than C as far as demonstrating such information is really transfered one always gets stuck using a C limited path to verify such. The end result is one cannot send a non-quantum message FTL via such methods. The problem is would one want to send a message and end up with the receiver getting a message different from the one you sent. Without the error checking method that's exactly what happens according to our best experiments at present.

[paultrr]

My question is how does one deliverately alter the state of a particle? It's my understanding that so far we have been able to observe various states (spin or charge) of a particle but that's about it.

 

We've been able to change spin on particles for sometime. I would suggest reading up on how entanglement works for an answer to that. We can do more than observe.

 

Spin is the internal angular momentum of the particle. It is assumed that the total angular momentum before the emission process is 0. Because of law of conservation of angular momentum it has to remain 0 if there is no exchange of angular momentum with environment. Lets assume that we conduct a spin measurement on particle A at any axis of choice. Spin is quantized. It can have only discrete values. The only values we can obtain for a spin ½ particle at a given axis are two possible orientations of spin opposite to each other along the choosen axis . Lets call them spin up and spin down. Prior to the measurement the spins of both particles are unknown. Lets assume that we find particle A in a spin up state. What is the consequence Of this measurement on spin of the particle B? If the angular momentum should be conserved , then the particle B should immediately undergo to a spin down state so that the vector sum of the spins remains 0, If we hadn’t done the measurement on particle A we would have both possibilities of spin up and spin down open also for particle B . But since we have measured spin of the particle A we know without doing the measurement on particle B that particle B must be in a spin down state. Thus the measurement on particle A immediately influences the outcome of the measurement that is conducted on particle B however far apart the particles A and B are from each other. May we consider the wave function itself as something physically real field or a probability wave, the situations after both measurements is certainly physically real since macroscopic measurement devices have changed their states. Thus correlation between the outcomes of measurements carried out at particle A and particle B shows that one cannot avoid but to accept that physical event at some location influences immediately the physical reality at some very distant location.

 

This consequence of the entanglement between two distant particles was until seventies only a theoretical issue. It was by Aspects experiments when the world realized that entanglement of distant photons is a fact(1). This was confirmed in later experiments(2).

 

The outcomes of two distant measurements are correlated , the correlation becomes apparent only if one can compare BOTH results. Each measurement itself is random. That is if one carries out 1000 measurements one sees a random distribution of outcomes for both particle A and particle B if evaluated independently. So no information is transferred from A to B and special relativity is not violated. The information can be obtained only if the outcomes are compared later by normal means. This has always been the assumption as far as proving something out. However, Relativity doesn’t concern itself with something so subtle like "information" in its terminology. In truth it is the energy/matter transport velocity or the velocity for influencing distant events each other what relativity limits. This misconception dates back to the times when it was discovered that the phase velocity of electromagnetic waves is exceeds light velocity c in a dispersive medium. Calculation and experience showed however that the group velocity namely the velocity with which a electromagnetic wave packet propagates is always less then c . Since electromagnetic waves are mainly used in signal transfer by modulations, this fact was expressed in the following way “although phase velocity can exceed light velocity the signal/information transfer velocity is always less then c”.

 

The Copenhagen interpretation, assumes the wave function is not a real physical entity but only a mathematical tool to predict the probability of a particular outcome in a measurement , nothing is physically transportat faster then light(3). But that is only one actual interpretation. If one assumes the wave function is real then one is left with a certain variety of information being transfered FTL. Roger Penrose has made the statement,

 

Although EPR-type experiments do not , in the ordinary sense of sending messages, conflict with causality of relativity , there is a definite conflict with the spirit of relativity in our picture of physical reality(4).

 

I happen to be one of those who agree and also tend to accept that the wavefunction is far more that a mathematical tool. I suspect there is a way to transfer information via this means. But at the current time our ability is simply too limited to do such. I also suspect that nature uses this type of path all the time and because of our inability to measure such paths we only get part of the picture. I think the mechanism of such involves an external frame of reference where the local velocity of light in that medium is different from ours. Such an external frame of reference would not actually violate relativity at all. And interesting enough this type of dual frames of reference has been showing up in articles related to brane theory, DSR, etc for sometime now. I have a couple of articles on one such model myself on the Cern server.

 

 

 

 

 

References

 

1.) Aspect 1982

2.) Chiao 1993 on the last page

3.) Stenger 1995 p.140

4.) Penrose 1989, p.370

[Moontanman]

All this talk about the view point of the observer and the observed has made me think of what a person actually traveling near the speed of light would see as their own speed. It seems to me if a person traveling close enough to the speed of light to have a time dilation of 1/10 would see themselves as traveling ten times the speed of light. At the very least their experience of the trip would seem to be faster than light, ten light years in one year.....

[Janus]

All this talk about the view point of the observer and the observed has made me think of what a person actually traveling near the speed of light would see as their own speed. It seems to me if a person traveling close enough to the speed of light to have a time dilation of 1/10 would see themselves as traveling ten times the speed of light. At the very least their experience of the trip would seem to be faster than light, ten light years in one year.....

 

 

Actually, they would see themselves moving at 0.995 times the speed of light. The reason they make the trip in 1 year by their clock is because, due to length contraction, the distance has shrunk to 1 light year from their perspective.

[Moontanman]

Actually, they would see themselves moving at 0.995 times the speed of light. The reason they make the trip in 1 year by their clock is because, due to length contraction, the distance has shrunk to 1 light year from their perspective.

 

I understand the whole length contraction but they wouldn't be able to see that contraction would they? To them it should be like they are traveling faster than light, or is it both? Or neither?

[Janus]

I understand the whole length contraction but they wouldn't be able to see that contraction would they?

 

Why not? Imagine there is a measuring tape stretching across that 10 ly distance marked off in meters. They fly along side it. They take a "snapshot" of one of the meter marks as they pass and compare them to a meter stick they have on board. They note that the "meter" marks on the tape are only spaced 1/10 of meter apart according to their stick. They count the number of marks they pass, divide by ten and get a number of meters traveled equal to 1 ly.

[Elena]

I have a question...

If you were in a car travelling at the speed of lightand then you turn the carlights on, would you see them?

I got this question from a comedian and was thinking this is actually a good question, and so was wandering if there was an answer.

[Moontanman]

I have a question...

If you were in a car travelling at the speed of lightand then you turn the carlights on, would you see them?

I got this question from a comedian and was thinking this is actually a good question, and so was wandering if there was an answer. :circle:

 

Well, since a material object cannot travel at the speed of light lets say the car was traveling at .999999% of the speed of light. From the occupant of the car's point of view the head lights would shine just like they would at regular speed.

[CraigD]

Actually, they would see themselves moving at 0.995 times the speed of light. The reason they make the trip in 1 year by their clock is because, due to length contraction, the distance has shrunk to 1 light year from their perspective.

Relativistic length contraction gets really fun when you consider that, from the point of view of an observer watching the fast moving spaceship or whatever, it is the length of the ship, not the distance it is traversing, that is contracted, leading to weird, but entirely explicable thought experiments like the ladder paradox. This thought experiment provides a great illustration of another important feature of special relativity: not only clocks and yardsticks, but simultaneity, too, is relative.