Tim_Lou Posted January 6, 2004 Report Posted January 6, 2004 nothing can be faster than the speed of light as we know. photons are traveling at that speed. when a person is driving a car, the person is moving at the view point of the earth.but to the car, the person is actually staying. if this is true, to a photon, we all are moving at the speed of light and that photon is not moving. but to two photon moving at opposite direction, to one of the photon, the speed is twice of the speed of light??? but isnt it like nothing can go faster than light speed??? when we say a photon is moving at the speed of light, what are we talking about? to what???movement is base on the view point of an object. is this right? or??? Quote
Tormod Posted January 6, 2004 Report Posted January 6, 2004 I think you need to read up on Einstein's theory of relativity. According to him, the speed of light is finite. Thus, if two objects move away from each other at the speed of light, both will perceive the other object as moving away at the speed of light. From someone observing these objects from a distance, both are moving at the speed of light (which is correct). It's like the question, "what happens if I drive at the speed of light and turn on the headlights of my car?". The light from the car will leave you at the speed of light. They will NOT leave at the speed of light plus the speed of light. this is rather counterintuitive, but that's what the theory says! But the entire question is meaningless, because objects such as cars cannot move at the speed of light. Check out this page: http://www.weburbia.demon.co.uk/physics/headlights.html Saying that the person inside the car is staying relative to the car is actually irrelevant. It does not matter whether an object is moving or the world around it - the speed of light is the same. Now, an interesting phenomenon is entanglement. When two entangled photons move away from each other at the speed of light, they STILL react instantly to events affecting one of them. This seems to be communication at a faster-than-light speed, and has been at the heart of many raging debates in particle physics (and still is, I think). Tormod Quote
lessthanadam Posted January 6, 2004 Report Posted January 6, 2004 http://science.howstuffworks.com/relativity.htm Einstein's theory of Relativity^ Quote
Tim_Lou Posted January 6, 2004 Author Report Posted January 6, 2004 i know what you are talking about. but there is one thing really confuse me. when a person is driving a car and a photon comes opposite, he should oberser the photon traveling at the sped of light. but if car goes the same direction of the photon travels, would it still be the speed of light?? if so, would the speed be slower to the first moving car??? one car is chasing the photon and one car is going oppisite way to the photon. would they observe the photon traveling at the speed of light????maybe the difference is too little. how about both cars moving at 99% of the speed of light?? if the speed is the same. to the photons, both cars stop??? whats the speed of the car to the photons??? Quote
Roberto Posted January 7, 2004 Report Posted January 7, 2004 It doesn´t matter the relative velocity of the two cars, both will see the photon with the same speed. What happens is that each car will perceive the space and time of the other distorted such that the light have always the same speed. This constancy of the speed of light is the origin of the time dilation and space contraction effects. Quote
Razorofoccam Posted January 15, 2004 Report Posted January 15, 2004 The photon has a velocity of 'C' [ 299,792,458 m/s (metres per second) ] The CAR has an indeterminaye delta V What WE 'see' is irrellevent. What IS... is what IS The SOL and the car continue on there paths as does EVERYTHING.FOR EVERYTHING..is in motion.motion is time... humans think that our descriptioms of observed reality.. define it.rubbish.WE interpret it. And NO more What we experience of Einstienian theory[fact]IS ALL that matters.. It says that humans [or any mass]who experience near SOL velocities will experiencemotion at a different rate to those who do not.WILL be subject to a different 'time' rate. That is, when we stop moving at near the SOL.the only resulting objective effect is that we have experienced LESStime/motion than the rest of reality. Observations while at near SOL velocity..interesting...but temporary. InUnity><Occam Quote
special j Posted February 4, 2004 Report Posted February 4, 2004 i'm not at all a mathematical person. so excuse me if i've misunderstood.. but is that then to say that if traveling at the speed of light, time would essentially cease for that in travel? Quote
Roberto Posted February 6, 2004 Report Posted February 6, 2004 The only observation is that you cannot travel at the speed of light. Only massless particles can (and in fact, they always do). Quote
maddog Posted January 8, 2005 Report Posted January 8, 2005 In answer to everyone on this post, find a book on Einstein's Special Theory of Relativity andread it ! Now, an interesting phenomenon is entanglement. When two entangled photons move away from each other at the speed of light, they STILL react instantly to events affecting one of them. This seems to be communication at a faster-than-light speed, and has been at the heart of many raging debates in particle physics (and still is, I think).Tormod Tormod: Yes. However, this means two photons had interacted at some point in theircommunative past to become entangled. This is where things get really weird. Informationcan now pass from one photon to the other instantaneously (no time). There have been afew Scientific American articles describing the latest findings in this branch of Physics (say last two years). Neat stuff! Maddog Quote
Tormod Posted January 8, 2005 Report Posted January 8, 2005 Information can now pass from one photon to the other instantaneously (no time). I thought information could not pass, only that when one of the particles is affected, it also happens to the other. I am not aware of any experiments where actual information has been passed. This would be a breakthrough in communication because it would mean FTL communication over vast distances. Quote
lindagarrette Posted January 8, 2005 Report Posted January 8, 2005 It's my understanding that when the entanglement occurs, the two particles are forever in sync so if one is observed, the condition of the other can be determined. The state of any particle cannot be deliberately altered. Now, my question is: how and why would the state of a particle change? Quote
paultrr Posted January 8, 2005 Report Posted January 8, 2005 If you alter the state of one particle in an entangled pair the other alters also. Now, here is the crux. By seperation distance these two particles are generally seen as requiring a certain amount of time for information from one to be shared with the other. Yet, from our present experiments if you alter one particle the other changes in an instant far faster than a normal light path signal or imformation exchange could take place. The quantum information being exchanged is that about the change itself. But, here is where this path rather breaks down as far as conventional information exchange goes. To actually measure the information exchanged requires an error correction or measurment process that is limited to C. So even if you could send inforation over an entangled path in general you are still required to prove that information was exchanged correctly over a normal light speed limited path. Thus almost any way to use this path is no better off than using a normal light speed limited path unless its quantum information like spin, etc that is being exchanged. Quote
hefner Posted January 8, 2005 Report Posted January 8, 2005 .. in an entangled pair.. To actually measure the information exchanged requires a ... measurment process that is limited to C. So even if you could send inforation over an entangled path in general you are still required to prove that ...What legislation requires me to "prove it" ?? did some judge issue a "show cause" order or somethin'? Quote
lindagarrette Posted January 9, 2005 Report Posted January 9, 2005 If you alter the state of one particle in an entangled pair the other alters also.. 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. Quote
jazzn85 Posted January 10, 2005 Report Posted January 10, 2005 http://plato.stanford.edu/entries/qt-entangle/#1 This website seems to sum up quantum entanglement farily well along with provide some examples of past experiments using entaglement. one mention describes how "David Deutsch first showed how to exploit quantum entanglement to perform a computational task that is impossible for a classical computer." Quote
lindagarrette Posted January 10, 2005 Report Posted January 10, 2005 Excellent. So constructing a NOT-gate allows one to deliberately change the characteristics of a particle going through. But is that a real process or just theory? Anyone? Quote
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