They do take account of that. ---------- Forwarded message ---------- From: Stephen A. Lawrence <[email protected]> Date: 2011/10/14 Subject: Re: [Vo]:CERN clocks subatomic particles traveling faster than light To: [email protected]
** On 11-10-14 02:53 PM, Daniel Rocha wrote: As far as I know, each GPS device sycs with several different satellites, or clocks, at least 3, and also corrections for gravitational effects from general relativity. That's not the point. The GPS system could be absolutely perfect and the problem would still exist. The point is they're using a time value which is "universal". An observer hanging in space, stationary, directly over the pole, looking down at GPS receivers all over the Earth would see that, at a given moment, they *all showed the same time* (modulo time zone changes). *And that's wrong!* If you time the speed of light using two clocks set that way, you'll find that it's anisotropic -- it's faster one way than the other. Note well: The observer hanging in space would say that the reason is that your start and end point were in motion, and the light had to travel farther one way than the other. An observer comoving with the Earth's surface, on the other hand, would say the two clocks were *not properly synced* -- relativity of simultaneity was not properly accounted for in setting them. In other words, if you sync your clocks using the GPS system, then you've automatically failed to take account of the motion of the Earth's surface. Maybe their problem was more subtle than this, but it doesn't sound like it. 2011/10/14 Stephen A. Lawrence <[email protected]> > OMG -- of course! You can't synchronize (all) clocks on the Earth's > surface -- it's a rotating frame, and Sagnac comes around and bites you on > the bumm if you try! Yet by using the GPS satellite signals, which are > available everywhere, they were doing essentially that: using a "universal" > time value, which doesn't produce a sensible result on the Earth's surface. > > Using clocks in another frame (the GPS clocks) to synchronize the clocks in > the rotating frame (on the surface of the earth) just adds confusion, it > doesn't avoid the problem, which is fundamental. In particular, if you sync > your (rotating) clocks with an external source, then when you measure light > speed you find it's anisotropic -- it's faster one way than the other. > > The only way to deal with it an experiment like this it is to pick just two > clocks and E-sync them using point-to-point two-way light travel (or use > some other source, but then figure out what the E-sync times would have been > and use the computed values). Apparently, they didn't do that. > > When I say it's "fundamental", I mean that if you use two-way light signals > to sync pairs of clocks on the Earth's surface, and you do it for a chain of > pairs of clocks reaching all the way around the Earth, you will find the > clocks at the beginning and the end of the chain are stubbornly out of sync, > even though the clocks all the way back along the chain were in sync. And > you can't avoid it by using some other clock source. > > See, for example, > > http://www.physicsinsights.org/sagnac_1.html > > > > > On 11-10-14 01:42 PM, Terry Blanton wrote: > >> On Fri, Sep 23, 2011 at 10:30 AM, Terry Blanton<[email protected]> >> wrote: >> >>> Don't bury Einstein yet: >>> >>> >>> http://www.newscientist.com/article/dn20957-dimensionhop-may-allow-neutrinos-to-cheat-light-speed.html >>> >>> "Sher also mentions a third option: that the measurement is correct. >>> Some theories posit that there are extra, hidden dimensions beyond the >>> familiar four (three of space, one of time). It's possible that the >>> speedy neutrinos tunnel through these extra dimensions, reducing the >>> distance they have to travel to get to the target. This would explain >>> the measurement without requiring the speed of light to be broken." >>> >>> Those neutrinos probably knew a short cut in the other 6 dimensions. >>> >> Well it wasn't extra dimensions. It was relativity itself. They >> needed entangled clocks! >> >> http://www.technologyreview.com/blog/arxiv/27260/?p1=blogs >> >> "Faster-Than-Light Neutrino Puzzle Claimed Solved by Special Relativity" >> >> T >> >> >> >
