Bobblehead Productions, In the opening statement of the first of two papers on the subject, the authors refer to the debate surrounding the "twins paradox" and how an experiment with macroscopic clocks might provide an empirical resolution. In Hafele and Keating's experiment, they flew cesium clocks around the world in opposite directions near the equator, and then measured how much time they have gained or lost when they return to the start point as compared to a stationary cesium clock to which they were originally synchronized. The experiment of Hafele and Keating HK actually differs from the twins paradox in some important ways - firstly, in the paradox, the traveling twin moves in a straight line to a distant point then turns around and comes back, with a series of accelerations and decelerations. In following a circular path, the HK experiment becomes a Sagnac effect experiment where it is clocks that are moving rather than beams of light. From the perspective of the observer on the ground, the moving clocks of Hafele and Keating have experienced similar motions with respect to the stationary earth bound clock.
|Published (Last):||24 February 2011|
|PDF File Size:||16.50 Mb|
|ePub File Size:||9.63 Mb|
|Price:||Free* [*Free Regsitration Required]|
Bobblehead Productions, In the opening statement of the first of two papers on the subject, the authors refer to the debate surrounding the "twins paradox" and how an experiment with macroscopic clocks might provide an empirical resolution. In Hafele and Keating's experiment, they flew cesium clocks around the world in opposite directions near the equator, and then measured how much time they have gained or lost when they return to the start point as compared to a stationary cesium clock to which they were originally synchronized.
The experiment of Hafele and Keating HK actually differs from the twins paradox in some important ways - firstly, in the paradox, the traveling twin moves in a straight line to a distant point then turns around and comes back, with a series of accelerations and decelerations.
In following a circular path, the HK experiment becomes a Sagnac effect experiment where it is clocks that are moving rather than beams of light. From the perspective of the observer on the ground, the moving clocks of Hafele and Keating have experienced similar motions with respect to the stationary earth bound clock. If their motions were truly "relative", then by the rules of SR both should arrive back at the starting point having experienced the same amount of time dilation in the same direction.
The actual result was that the westward travelled clock increased in its time rate more time had elapsed and the eastward travelled clock decreased in its time rate.
The expected time dilation on clocks used by Hafele and Keating is shown below in Fig. The height and velocity terms were predicted by Einstein in and — however the Sagnac term was unknown to Einstein when he wrote his papers on special relativity, so this effect was never anticipated by Einstein.
Nevertheless, the relative timekeeping behavior of terrestrial clocks can be evaluated by reference to hypothetical coordinate clocks of an underlying non-rotating inertial space 6.
Builder, Aust. Physics 11, ]. Although inertial systems are highly specialized, they have an objective physical relationship with the universe because they have no acceleration or rotation relative to the universe. This demand is also implied by the relativistic equations of electrodynamics and even by the formulation of the restricted theory itself.
The observable effects of absolute accelerations and of absolute velocities must be ascribed to interaction of bodies and physical systems with some absolute inertial system. We have no alternative but to identify this absolute system with the universe. Thus in the context of physics, absolute motion must be understood to mean motion relative to the universe, and any wider or more abstract interpretation of the "absolute" must be denied.
Interactions of bodies and physical systems with the universe cannot be described in terms of Mach's hypothesis, since this is untenable. There is therefore no alternative to the ether hypothesis. The equation is displayed below:. This version is shown below:. We will restrict ourselves in this discussion to the case where the trains travel at the same sea level altitude, so gravitational time dilation need not be considered.
Thence we conclude that a balance-clock at the equator must go more slowly, by a very small amount, than a precisely similar clock situated at one of the poles under otherwise identical conditions. See " On the Electrodynamics of Moving Bodies p. As shown in Fig. Definition of a preferred frame of reference: A frame is said to be physically privileged, when there is some essential physical difference between it and the others. In most historical aether theories, the essential physical difference is that it is the only frame where the speed of light is constant.
Here lies the problem - if you have a series of clocks around the equator of the earth and you carry a portable clock eastward to synchronize each successive clock, when you reach the last one, the first clock will lead the last clock by However, this is tantamount to establishing the ECI frame as a preferred reference frame for motion above all others.
Does this not make the fixed stars a physically privileged reference frame? Einstein Assertion 5: "We will raise this conjecture the purport of which will hereafter be called the Principle of Relativity" to the status of a postulate, and also introduce another postulate, which is only apparently irreconcilable with the former, namely, that light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body.
Consider the diagram in Fig. We have two optical setups on a table, both perfectly stationary with respect to the laboratory observer. A beam of light is emitted in a pulse from each source and the light follows the paths shown in red, returning to the detectors where the propagation speed in calculated based on the elapsed time and the path distance. In the setup on the left, the speed of light is measured as C. For the path on the right, something more interesting happens.
If the beam goes clockwise, the light beam will be measured to have exceeded the speed of light! We conclude from this experiment that the measured speed of light is not constant. This is similar to the situation of Fig. The argument usually goes that the setup on the right encloses an area and therefore experiences the Sagnac effect due to the rotation of the earth, and thereby the table is not an inertial frame.
However, the two setups share the same frame of reference - so either both setups are invalid for SR, or both are valid. If an argument is going to be made that a speed of light test is invalid because the frame is rotating, or the observer is rotating, then we have to discard all speed of light tests to date since every place that humans have performed a test on the earth or in near space have always been experiencing some form of rotation, either diurnal or orbital, which in modern times has become readily visible.
As Hafele and Keating say in their paper, inertial motion must be referenced to a universal reference frame. Another common argument is to say that the path length has changed due to the rotation and this is why the speed of light is not measured to be C. But for our figure 3B the path length does not change for our laboratory observer since the loop is stationary in his frame.
A singular frame where the speed of light is constant, just like in aether theories? Relative inertial frames of reference existed only to the extent that we could not detect their rotation — now that we can routinely detect diurnal rotation in our optical instruments and clocks, can we really say that a purely inertial frame of reference still exists independent of the non-rotating universe?
Fig 4: A Sphere of contradiction. I personally do not consider the Sagnac effect relativistic simply because it involves time dilation - the concept of time dilation was not conceived of by Einstein, but rather by Lorentz and Larmor. Further, time dilation can be construed as simply an error in clock readings, as discussed here. Some have cited Max van Laue as discussing the effect after the proposal of Michelson in , before Einstein was even known in terms of special relativity in This is what Silberstein said about relativity and the Sagnac Effect:.
Appendix A. Redefining Motion after the Hafele and Keating Experiment. The following description would seem to be implied from the explanation of Hafele, Keating and Builder.
Shown below is a drawing of our earth and sun moving through space. This is the observer shown below holding the red loop. This observer is the one referred to as an "inertial observer".
If he sends clocks around the loop, their rate of time will be slower in either direction. This should also be true if he moves in a straight line from his stationary position at some absolute velocity. Let's place such an observer on the earth shown with the green loop. This observer is non-inertial since he is experiencing three different rotations with respect to the CMBr - diurnal, solar, and galactic.
Because of this, no matter how he orients his loop, the measured speed of light around it will never be exactly C, and will differ in each direction. His clocks moving around the loop will count faster or slower depending on their direction. The equation is displayed below: Fig. The clock on the train travelling east counted slower compared to the stationary clock at To.
The time lost on the eastbound train was 20X higher than that lost on the north and southbound trains. Ref: A. However, in all other directions it is off by up to 20x the predicted value.
1.2: Experimental Tests of the Nature of Time
In , J. Hafele and R. Keating of the U. Naval Observatory brought atomic clocks aboard commercial airliners and went around the world, once from east to west and once from west to east. As in the parable of Alice and Betty, Hafele and Keating observed that there was a discrepancy between the times measured by the traveling clocks and the times measured by similar clocks that stayed at the lab in Washington.
From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U. Relative to the atomic time scale of the U. These results provide an unambiguous empirical resolution of the famous clock "paradox" with macroscopic clocks. In , experimenters from the U. Naval Observatory undertook an experiment to test time dilation. They made airline flights around the world in both directions, each circuit taking about three days. They carried with them four cesium beam atomic clocks.
Hafele and Keating Experiment
The Hafele—Keating experiment was a test of the theory of relativity. In October , Joseph C. Hafele, a physicist, and Richard E. Keating, an astronomer, took four cesium-beam atomic clocks aboard commercial airliners. They flew twice around the world, first eastward, then westward, and compared the clocks against others that remained at the United States Naval Observatory. When reunited, the three sets of clocks were found to disagree with one another, and their differences were consistent with the predictions of special and general relativity. From the actual flight paths of each trip, the theory predicted that the flying clocks, compared with reference clocks at the U.