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quote:Originally posted by DoctorBeaver& here's another 1. If spacetime really is curved, photons will eventually come back whence they originated. Does that mean that if we wait long enough we will eventually see ourselves as we were n number of years ago? We learn from history that we do not learn from history. (Georg Hegel)
quote:Eventually, the rate of expansion will approach the speed of light, 186,321 miles a second. As far as scientists know, nothing can move faster than that in a local area. But over the gigantic scale of the universe, galaxies moving at close to the speed of light can separate at a relative speed that exceeds the universal limit. At this point, light coming from distant galaxies never catches up to telescopes on Earth because the planet is moving away too fast.
quote:Originally posted by DoctorBeaverBut just hang on a minute. As an object approaches c, the slower it appears to move to an outside observer (isn't that why an object entering a black hole would appear to freeze at the event horizon?), Therefore the faster those galaxies travel, the slower we would see them moving & therefore gain the impression that the expansion was slowing down! And if all that is true, how do we see anything accelerating - as a car pulled away from traffic lights, it should appear to slow down! AAAARRRRRGH I think I'll stick to psychology, it's not quite so baffling [xx(]
quote:Does anyone have a link to the experiments dont a year or two ago where a doped medium was produced in which the light traversed the pathway through the medium at a value of c whose velocity was greater than that of c in a vaccum.
quote:Originally posted by DoctorBeaverAnother_someone - I'm not confusing speed with acceleration. Speed is a function of acceleration whereby at any given point in time the speed of an accelerating object has increased from that at any earlier point in time.
quote:The experiment with the 2 atomic clocks (1 in a plane, the other stationary on the ground) showed that from the point of view of the stationary 1, time for the moving 1 had passed slower. At c, this effect reaches its maximum conclusion & to an outside observer, time would cease to pass for the moving object. If no time appears to pass then to the outside observer that object must appear to be stationary.Oooh, how I love playing with logic in a non-logical world! 
quote:Originally posted by another_someoneThus, if a person were accelerated up to the speed of light, they would stop ageing, and to them, the entire lifespan of the universe would pass by them in an infinitesimally short time, but they would still only (to the outside observer) be travelling at the speed of light, no more and no less. You might say that if time stops for the person who is travelling at the speed of light, that is tantamount to their perceiving that they are travelling at infinite speed, but that is their perception, not the perception of someone of the outside. Ofcourse, one might say that if they believe they are travelling at infinite speed, then they would also believe that the outside world is travelling at infinite speed relative to them, and thus not constrained by the speed of light – that is where I get lost.
quote:The experiment with the 2 atomic clocks (1 in a plane, the other stationary on the ground) showed that from the point of view of the stationary 1, time for the moving 1 had passed slower. At c, this effect reaches its maximum conclusion & to an outside observer, time would cease to pass for the moving object. If no time appears to pass then to the outside observer that object must appear to be stationary.
quote:Originally posted by Solvay_1927As for my links in my last posting above ... has anyone looked at these? I'm interested to know if they're valid. (Have the experiments been verified and repeated?) Because I find them a bit confusing - I don't understand why the results DON'T violate relativity theory. They seem to suggest that FTL (faster than light) signalling) IS possible through certain mediums.Can anyone shed more light (excuse the pun) on these experiments?Solvay."Eagles may soar, but weasels don't get sucked into jet engines."
quote:So, while the New Jersey researchers showed that a pulse can be shown to go faster than a speed of light, they have not managed show that a message can be transmitted at that speed.
quote:Originally posted by ukmickyI think quantum entanglement also runs into the same information hurdle as effects moving at superluminal speeds run into the uncertainty principle making it impossible to control any signals, and because you dont know what your going to get untill you observe it
quote:Although it seems as if the Bell inequality, at least as it is usually presented, does not give us the convincing reasons for believing in the non-locality of physics which it has often been claimed to, it may be that there are other reasons for believing in non-local causes. Greenberger, Horne and Zeilinger (1989) have presented a scheme which avoids the criticisms I have presented, and if correct really seems to leave no room for a local interpretation. However, this scheme has not yet been tested experimentally. The GHZ scheme uses three particles rather than two, and measurements of spin rather than polarisation. The particles are sent out in different directions, and one of two sorts of spin measurement is made on each – call the first type X and the second type Y. The measurements are made in one of four combinations: Either every particle will be asked X, or two of the particles will be asked Y, and the other one X. Quantum mechanics predicts a 100% probability that if only X measurements are made, an odd number of the particles will be found in the ‘spin-up’ state, whereas if two Y measurements are made, an even number of particles will be measured as ‘spin-up’. The theory says nothing about whether the odd number will be 1 or 3, or the even number 2 or 4. In this arrangement (assuming it is not eventually disproved, either by experiment or by the unlikely discovery of a theoretical error) it seems to be truly impossible to find a local explanation for the correlations; if each particle were to decide in advance what it will answer in response to the two questions, a single run of the experiment would stand at least a one in four chance of showing results that are in conflict with quantum mechanical predictions. Another area of quantum theory which may be irreconcilable with locality is the Aharonov-Bohm effect, whereby particles travelling through a field-free region are influenced by a nearby magnetic field. Richard Healey18 argues that the apparent non-locality of this effect is closely analogous to that manifested in violations of Bell’s inequality.
quote:Originally posted by Solvay_1927I understand what you're saying, Someone and Michael. But I'm still not convinced. Maybe I'm just misunderstnding the experiment described in the earlier links above.My understanding is that you have a container (containing ultra-cold caesium gas) which is, say, 30cm thick. If a person on the left side of this container switches on a laser (of the right wavelength) at time t=0, a person on the right of the container sees light starting to come out his side at t<1 ns (ie. less than 1 nanosecond later). But light in a vacuum would take a full nanosecond to traverse 30cm.So you've got a "signal" being communicated faster than light. (The signal isn't a complicated message, it's just a simple "the laser has been switched on". Like a binary 0/1 communication.)Like I said, maybe I've misunderstood the experiment. That's why I'd be interested in whether anyone has a more detailed explanation of what this experiment was about. (And why can't I find any references to this experiment dated later than 2000? Did they realise they'd made a mistake and quietly brush this false result under the carpet?)Help.Solvay."Eagles may soar, but weasels don't get sucked into jet engines."
quote:Originally posted by Solvay_1927(Which reminds me of a question that I heard some time ago: How do you tell if you're out of invisible ink?)