Ives-Stilwell experiment
Encyclopedia
The Ives–Stilwell experiment exploits the transverse Doppler effect (TDE). This was the first direct, quantitative confirmation of the time dilation
factor. Together with the Michelson–Morley and Kennedy–Thorndike experiments, it forms one of the fundamental tests of special relativity
theory. Other tests confirming the relativistic Doppler effect, are the Mössbauer rotor experiment and modern Ives–Stilwell experiments. For other time dilation experiments in general, see Time dilation of moving particles. For other tests in general, see Tests of special relativity.
in his seminal 1905 paper.
Einstein subsequently suggested an experiment based on the measurement of the relative frequencies of light perceived as arriving from a light source in motion with respect to the observer. Herbert E. Ives
and G. R. Stilwell (although they referred to time dilation as following from the "theory of Lorentz and Larmor
") undertook the task of executing the experiment and they came up with a very clever way of separating the much smaller TDE from the much bigger longitudinal Doppler effect. The experiment was executed in 1938 and it was reprised multiple times (see, e.g.). Similar experiments were conducted several times with increased precision, by Otting (1939), Mandelberg et al. (1962),
Hasselkamp et al. (1979),
Ives remarked, that it is nearly impossible to measure the transverse Doppler effect with respect to light rays emitted by canal rays
, at right angles to the direction of motion of the canal rays (as it was considered earlier by Einstein), because the influence of the longitudinal effect can hardly be excluded. Therefore he developed a method, to observe the effect in the longitudinal direction of the canal rays' motion. If it is assumed that the speed of light is fixed with respect to the observer (“Classical Theory”), then the forward and rearward Doppler-shifted frequencies seen on a moving object will be f'/f = c/(c±v), where v is recession velocity. Under special relativity, the two frequencies will also include an additional “Lorentz factor
” redshift
correction.
When we invert these relationships so that they relate to wavelengths rather than frequencies, “Classical Theory” predicts redshifted and blueshifted wavelength values of 1+v/c and 1-v/c, so if all three wavelengths (redshifted, blueshifted and original) are marked on a linear scale, according to Classical Theory the three marks should be perfectly evenly spaced.
|.....|.....|
But if the light is shifted by special relativity's predictions, the additional Lorentz offset means that the two outer marks will be offset in the same direction with respect to the central mark.
|....|......|
Ives and Stilwell found that there was a significant offset of the centre of gravity of the three marks, and therefore the Doppler relationship was not that of "Classical Theory". This approach had two main advantages:
A more precise confirmation of the relativistic Doppler effect was achieved by the Mössbauer rotor experiments. From a source in the middle of a rotating disk, gamma rays are being sent to a receiver at the rim (in some variations this scheme was reversed). Due to the rotation velocity of the receiver, the absorption frequency decreases if the transverse Doppler effect exists. This effect was actually observed using the Mössbauer effect
. The maximal deviation from time dilation was
, thus the precision was much higher than that (
) of the Ives–Stilwell experiments. Such experiments were performed by Hay et al. (1960),
Champeney et al. (1963, 1965), Kündig (1963).
Isotropy of the speed of light
Moessbauer rotor experiments were also used to measure a possible anisotropy of the speed of light. That is, a possible aether wind should exert a disturbing influence on the absorption frequency. However, like in all other aether drift experiments (Michelson–Morley experiment), the result was negative, putting an upper limit to aether drift of 3–4 m/s. Experiments of that kind were performed by Champeney & Moon (1961), Champeney et al. (1963) and Turner & Hill (1964).
storage ring
s, as the TSR at the MPIK
, the Doppler shift of lithium
ions traveling at high speeds is evaluated by using Saturated spectroscopy
. Due to their frequencies emitted, these ions can be considered as optical atomic clock
s of high precision.
ions, moving within a 75 m long, phase-stabilized optical fiber
. These optical atomic clocks emitted frequencies of a certain frequency, and the sensitivity of this experiment was
. Therefore, it was possible to measure a frequency shift due to time dilation of 
at speeds below 36 km/h (< 10 m/s), by comparison of the rates of moving and resting clocks.
Time dilation
In the theory of relativity, time dilation is an observed difference of elapsed time between two events as measured by observers either moving relative to each other or differently situated from gravitational masses. An accurate clock at rest with respect to one observer may be measured to tick at...
factor. Together with the Michelson–Morley and Kennedy–Thorndike experiments, it forms one of the fundamental tests of special relativity
Special relativity
Special relativity is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies".It generalizes Galileo's...
theory. Other tests confirming the relativistic Doppler effect, are the Mössbauer rotor experiment and modern Ives–Stilwell experiments. For other time dilation experiments in general, see Time dilation of moving particles. For other tests in general, see Tests of special relativity.
Ives–Stilwell experiment
The TDE was described by Albert EinsteinAlbert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...
in his seminal 1905 paper.
Einstein subsequently suggested an experiment based on the measurement of the relative frequencies of light perceived as arriving from a light source in motion with respect to the observer. Herbert E. Ives
Herbert E. Ives
Herbert Eugene Ives was a scientist and engineer who headed the development of facsimile and television systems at AT&T in the first half of the twentieth century. He was also a critic of the special theory of relativity, and attempted to disprove the theory by means of logical arguments and...
and G. R. Stilwell (although they referred to time dilation as following from the "theory of Lorentz and Larmor
Lorentz ether theory
What is now often called Lorentz Ether theory has its roots in Hendrik Lorentz's "Theory of electrons", which was the final point in the development of the classical aether theories at the end of the 19th and at the beginning of the 20th century....
") undertook the task of executing the experiment and they came up with a very clever way of separating the much smaller TDE from the much bigger longitudinal Doppler effect. The experiment was executed in 1938 and it was reprised multiple times (see, e.g.). Similar experiments were conducted several times with increased precision, by Otting (1939), Mandelberg et al. (1962),
Hasselkamp et al. (1979),
Ives remarked, that it is nearly impossible to measure the transverse Doppler effect with respect to light rays emitted by canal rays
Anode ray
Anode rays are beams of positive ions that are created by certain types of gas discharge tubes. They were first observed in Crookes tubes during experiments by the German scientist Eugen Goldstein, in 1886. Later work on anode rays by Wilhelm Wien and J. J...
, at right angles to the direction of motion of the canal rays (as it was considered earlier by Einstein), because the influence of the longitudinal effect can hardly be excluded. Therefore he developed a method, to observe the effect in the longitudinal direction of the canal rays' motion. If it is assumed that the speed of light is fixed with respect to the observer (“Classical Theory”), then the forward and rearward Doppler-shifted frequencies seen on a moving object will be f'/f = c/(c±v), where v is recession velocity. Under special relativity, the two frequencies will also include an additional “Lorentz factor
Lorentz factor
The Lorentz factor or Lorentz term appears in several equations in special relativity, including time dilation, length contraction, and the relativistic mass formula. Because of its ubiquity, physicists generally represent it with the shorthand symbol γ . It gets its name from its earlier...
” redshift
Redshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
correction.
When we invert these relationships so that they relate to wavelengths rather than frequencies, “Classical Theory” predicts redshifted and blueshifted wavelength values of 1+v/c and 1-v/c, so if all three wavelengths (redshifted, blueshifted and original) are marked on a linear scale, according to Classical Theory the three marks should be perfectly evenly spaced.
But if the light is shifted by special relativity's predictions, the additional Lorentz offset means that the two outer marks will be offset in the same direction with respect to the central mark.
Ives and Stilwell found that there was a significant offset of the centre of gravity of the three marks, and therefore the Doppler relationship was not that of "Classical Theory". This approach had two main advantages:
- didn't require us to commit to an exact value for the velocity involved (which might have been theory-dependent), and
- it didn't require an understanding or interpretation of angular aberration effects, as might have been required for the analysis of a "true" transverse test. A "true transverse test" has been run almost 40 years later, by Hasselkamp in 1979.
Mössbauer rotor experiments
Relativistic Doppler effectA more precise confirmation of the relativistic Doppler effect was achieved by the Mössbauer rotor experiments. From a source in the middle of a rotating disk, gamma rays are being sent to a receiver at the rim (in some variations this scheme was reversed). Due to the rotation velocity of the receiver, the absorption frequency decreases if the transverse Doppler effect exists. This effect was actually observed using the Mössbauer effect
Mössbauer effect
The Mössbauer effect, or recoilless nuclear resonance fluorescence, is a physical phenomenon discovered by Rudolf Mössbauer in 1958. It involves the resonant and recoil-free emission and absorption of γ radiation by atomic nuclei bound in a solid...
. The maximal deviation from time dilation was
, thus the precision was much higher than that () of the Ives–Stilwell experiments. Such experiments were performed by Hay et al. (1960),Champeney et al. (1963, 1965), Kündig (1963).
Isotropy of the speed of light
Moessbauer rotor experiments were also used to measure a possible anisotropy of the speed of light. That is, a possible aether wind should exert a disturbing influence on the absorption frequency. However, like in all other aether drift experiments (Michelson–Morley experiment), the result was negative, putting an upper limit to aether drift of 3–4 m/s. Experiments of that kind were performed by Champeney & Moon (1961), Champeney et al. (1963) and Turner & Hill (1964).
Fast moving clocks
A considerably higher precision has been achieved in modern variations of Ives–Stilwell experiments. In heavy ionHeavy ion
Heavy ion refers to an ionized atom which is usually heavier than helium. Heavy-ion physics is devoted to the study of extremely hot nuclear matter and the collective effects appearing in such systems, differing from particle physics, which studies the interactions between elementary particles...
storage ring
Storage ring
A storage ring is a type of circular particle accelerator in which a continuous or pulsed particle beam may be kept circulating for a long period of time, up to many hours. Storage of a particular particle depends upon the mass, energy and usually charge of the particle being stored...
s, as the TSR at the MPIK
Max Planck Institute for Nuclear Physics
The Max-Planck-Institut für Kernphysik is aresearch institute in Heidelberg, Germany.The institute is one of the 80 institutes of the Max-Planck-Gesellschaft , an independent, non-profit research organization. The Max Planck Institute for Nuclear Physics has been founded in 1958 under the...
, the Doppler shift of lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
ions traveling at high speeds is evaluated by using Saturated spectroscopy
Saturated spectroscopy
Saturated spectroscopy is the method by which the exact energy of the hyperfine transitions within an atom can be found. When a monochromatic light is shone through an atom, the Absorption cross section is broadened due to Doppler broadening...
. Due to their frequencies emitted, these ions can be considered as optical atomic clock
Atomic clock
An atomic clock is a clock that uses an electronic transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element...
s of high precision.
| Author | Year | Maximum deviation from time dilation |
|---|---|---|
| Grieser et al. | 1994 |  |
| Saathoff et al. | 2003 |  |
| Reinhardt et al. | 2007 |  |
Slow moving clocks
Meanwhile, the measurement of time dilation at every day's speeds has been accomplished as well. For that purpose, Chou et al. (2010) used aluminiumAluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
ions, moving within a 75 m long, phase-stabilized optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
. These optical atomic clocks emitted frequencies of a certain frequency, and the sensitivity of this experiment was
. Therefore, it was possible to measure a frequency shift due to time dilation of at speeds below 36 km/h (< 10 m/s), by comparison of the rates of moving and resting clocks.External links
- Modern Reenactments of Relativity Tests
- M Moriconi, 2006, Special theory of relativity through the Doppler effect
- Warp Special Relativity Simulator Computer program demonstrating the relativistic doppler effect.
- The Doppler Effect at MathPages