0 Members and 1 Guest are viewing this topic.
Austrian physicists Josef Lense and Hans Thirring … predicted that the rotation of a massive object would distort spacetime metric, making the orbit of a nearby test particle precess. This does not happen in Newtonian mechanics for which the gravitational field of a body depends only on its mass, not on its rotation. The Lense-Thirring effect is very small—about one part in a few trillion. To detect it, it is necessary to examine a very massive object, or build an instrument that is very sensitive. Linear frame dragging is the similarly inevitable result of the general principle of relativity, applied to linear momentum. Although it arguably has equal theoretical legitimacy to the "rotational" effect, the difficulty of obtaining an experimental verification of the effect means that it receives much less discussion and is often omitted from articles on frame-dragging
I personally don't think it would make any difference to speed c. (Although with absorption and re-emission it may appear to). The way I see it is light travels instantaneously in its own reference frame (please excuse my use of inadequate language). In other words it travels at infinite speed and that infinite speed cannot be added to or subtracted from.
Looks like an experiment to measure "linear frame dragging" …
This also means that light traveling in the direction of rotation of the object will move past the massive object faster than light moving against the rotation, as seen by a distant observer.
Quote from: MikeS on 10/01/2012 07:39:07I personally don't think it would make any difference to speed c. (Although with absorption and re-emission it may appear to). The way I see it is light travels instantaneously in its own reference frame (please excuse my use of inadequate language). In other words it travels at infinite speed and that infinite speed cannot be added to or subtracted from.Except, it isn't quite an infinite speed. It has been measured to be 299,792,458 metres per second in a vacuum.The speed varies based on the medium, so it is slower in water than in air. Varying speed in different mediums is more complicated than absorption/re-emission, as I believe the spectrum isn't changed, except for light that is actually absorbed. In this case, though, I am proposing to shine the light through a gap between two moving objects, done in a vacuum, hopefully avoiding interference with the medium.If the observer is moving, then it can be red-shifted, or blue shifted depending on the direction of the observer, but the speed measurement is the apparently the same. We are also seeing this red-shifting and blue-shifting with the distance and direction of movement of stars.Anyway, my thought is to essentially have a fixed emitter, fixed observer, but move the "space" between the two.
According to General Relativity... Both speed detectors would measure the speed of light in their spinning disk frame at precisely the "speed of light", C, despite each detector going in the opposite direction at a rapid rate. There would be some red-shifting or blue-shifting of the wavelength in the spinning disk frame.So, wouldn't you have to conclude that the light has either slowed down, or sped up in the overall frame.
Back to the original experiment, one option to enforce the "frame" would be to use a glass disk, but that would induce a host of problems, so, I chose to suggest using a vacuum, with a narrow, empty gap between the disks.
Surely you don't have to measure the speed of light with a roundtrip back to the source.I believe one method to get an actual measurement of the speed of light is to have it pass through a series of shutters. Then, calculate the delay between the opening and closing of the shutters, when the light actually passed through.
...sorry, you cannot view external links. To see them, please
REGISTER or LOGIN
...the length of time you spend moving the clock will also fall increasingly more with speed rather than in proportion to speed because the distance you're taking the clock will contract at higher speeds at exactly the rate required to ensure that no matter what speed you move the clock at you will end up with the same overall slowing (or speeding up) of that clock.
So, when we say the speed of light is invariant, it is only in reference to a two-way measurement.
One possible frame of reference would be the Cosmic Microwave Background Radiation.
It should be easy enough to do a one-way light experiment in space.
Say you put 2 satellites in geosynchronous orbit, at an elevation of about 42,000 km. Two satellites on opposite sides of the globe would be about 84,0000 km apart.The speed of light is about 300,000 km/sec.So, your two geosynchronous satellites are about 0.28 light seconds apart.
One trick might be to synchronize the clocks without respect to the CMBR, and the one-way speed of light. But, this could be done by synchronizing them with respect to a solar eclipse. You would still have the half degree progression of the solar orbit in a half a day.... but should be able to throw that into one's calculations.
Synchronize their clocks with a known eclipse (Jupiter eclipse, or to one's favorite star whatever), and run satellite to satellite communication pulses.
That's not how Relativity was created. SR comes from one idea, a axiom of sorts, still undisputed experimentally.
But, the experiment I'm proposing to determine the one-way speed of light... which I think could be calculated to an accuracy of a couple of m/s, would take a huge bite out of Special Relativity.
But it is also so that no matter how fast you move with your 'local clock' it will never change its pace, and according to it your 'aging/decay' will come at a natural pace locally. So what you do there is to assume that there should be some 'global' definition of time. There isn't, and that's one of the things why so many want to get rid of 'times arrow' as a 'global phenomena', because it doesn't exist in reality, only locally.
And that you can check very easily using two clocks giving them different 'relative motion'. They will start to differ, but when you reintroduce them into one same frame of reference again (impossible as I think of it for fermions, aka matter) they will share a same 'clock beat' no matter what you measured before between those clocks 'differing', so that is your reality check of what 'times arrow' is, well as I see it.
Anyway, you wrote "his theory philosophically requires an aether for every possible frame of reference to maintain separations between objects, whereas Lorentz's requires only one."That's not how Relativity was created. SR comes from one idea, a axiom of sorts, still undisputed experimentally. 'c'.That and 'frames of reference'
Quote from: CliffordK on 13/01/2012 17:21:27But, the experiment I'm proposing to determine the one-way speed of light... which I think could be calculated to an accuracy of a couple of m/s, would take a huge bite out of Special Relativity.It won't work - you can't just divide an orbit in two and asume that it takes 11 hours 58 minutes (half the time the Earth takes to rotate) for a geostationary satellite to get from one point to the opposite point and then another 11 hours 58 minutes to get back to the first. The whole system could be travelling close to the speed of light, in which case it will take a very long time for the satellite to travel round the half of the orbit that takes it from behind the Earth to in front of it, and then it will race back the other way in a tiny fraction of the time. While it does this, its clocks will be slowed during the slow half of the orbit and run close to full speed on the way back, making both halves appear to take the same length of time. The result of this is that the effect you're trying to measure will be cancelled out completely and you will detect nothing, just like every other experiment.
It all depends on your definition of time, which I fear has gotten distorted over the past century. 
However, looking at the external Earth and Sun would be invariant in different space frames. Only if you are in a spaceship leaving Earth, it would appear to slow down due to seeing the light arrive later. But, the correction is quite simple based on distance from Earth.
Your perception of the speed of the light from the light source you are approaching necessarily speeds up.Your perception of the speed of the light from the light source behind you necessarily speeds down.
Part of the reason that the light you are approaching has to speed up is that if, for example, you were measuring the passing of light with a series of shutters. Light would pass through the first shutter, starting the time. Then your train would move so that the endpoint is closer to the start point, and thus it must arrive at the end point earlier. Likewise, if the second shutter is receding from the source, the light would arrive at the endpoint later.
So, if you have two sources of light, then by relativity, for both speeds to be equal, one must have a clock that both runs fast and slow simultaneously.
Let's rule out one possibility first by testing the idea that the speed light travels through the equipment is modified by the speed of the equipment such that it always appears to be the same when measured by the shutter method. Imagine two trains travelling in opposite directions at high speed. Light is sent in the same direction through both trains. Let's put the light source between the trains, then split the beams to send them into the two trains, and then use mirrors to send the light down the middle of the trains. The shutters are moving with the trains. At the end, more mirrors reflect the light back out into the space between the trains where a detector times the arrival of the two beams, where both arrive simultaneously. If the light was actually moving faster in one train than the other, the two beams would not arrive at the same time, but they must do - if they didn't it would be possible to send information faster than the speed of light by sending the message into the other train and transmitting it the length of that train before sending it back into the first train. This means that the shutters should show up something - one of the rear shutters will open and close too soon while the other won't open in time. To any observer on either train though, it will look as if the timing between the shutters opening is wrong, but we can now determine that the timing is right because we synchronised the timers when they were together and then moved then slowly to their positions by the shutters, and confirm it by bringing the timers back together to compare them again.
...sorry, you cannot view external links. To see them, please
REGISTER or LOGINUnfortunately I only have the article in abstract form, and can not tell for sure if the experiment was ever conducted. Anyway, I'll be headed to the local library early next week, and it will give me some bibliographies to bounce around. Their suggestion was to separate the sender/receiver by less than 1km, generating an accuracy on the order of 100,000 m/s. My suggestion with satellite technology, with newer technology, and separating the devices by up to 84,000 km, it drops the error down to the range of 1m/s.However, right now I'm concentrating on potential flaws in hydrogen or cesium clocks that could effectively reduce the accuracy, thus generating a false negative (or potentially a false positive) result.Hafele and Keating found a systematic inconsistancy in their atomic clock experiment on the order of +273/-59 nanoseconds, and the GPS system has a systematic inconsistency of about 38 microseconds per day. If the inconsistencies are uniform, then the satellite experiment should provide useful data. However, if the clock inconsistencies are non-uniform, then they could wreck havoc with the experiment.Obviously the orbital motion of the Earth should provide a much appreciated control for the experiment.
As far as a light-clock.It would be pretty easy.
But, for example, one might be able to define the diameter of the helium atom 4He as a fundamental distance. Perhaps add some additional parameters including pressure, and temperature.Then, one could define a basic unit of time as that time it takes for a two-way light beam to travel the distance of the diameter of helium.Or... use the nucleus, if that is more invariable than the electron cloud.
Ok, synchronizing clocks is still an issue.I think there is something to the light clock.I've made another diagram to study wavelengths and movements. Mirrors reflect the light waves back towards the source. Propagation waves shown with respect to the rest frame of the fabric of space. [ Invalid Attachment ] In this example, in all directions the viewer sees green, independent of the actual frame movement. In fact, it is exceedingly difficult to discriminate between the wavelength/frequency functions (and thus the theory of Relativity).