Cryogenic test probes Einstein's equivalence principle, general relativity, and spacetime 'foam'

January 5, 2017 by Lisa Zyga feature
Illustration of the experimental set-up, in which scientists attempted to detect any change in the length of a cryogenic silicon resonator. They detected no change, in support of the equivalence principle. Credit: Wiens et al. ©2016 American Physical Society

(Phys.org)—Physicists have performed a test designed to investigate the effects of the expansion of the universe—hoping to answer questions such as "does the expansion of the universe affect laboratory experiments?", "might this expansion change the lengths of solid objects and the time measured by atomic clocks differently, in violation of Einstein's equivalence principle?", and "does spacetime have a foam-like structure that slightly changes the speed of photons over time?", an idea that could shed light on the connection between general relativity and quantum gravity.

In their study published in Physical Review Letters, E. Wiens, A.Yu. Nevsky, and S. Schiller at Heinrich Heine Universität Düsseldorf in Germany have used a cryogenic to make some of the most precise measurements yet on the length stability of a solid object. Overall, the results provide further confirmation of Einstein's equivalence principle, which is the foundation on which the theory of is based on. And in agreement with previous experiments, the researchers found no evidence of spacetime foam.

"It is not easy to imagine ways of testing for consequences of the expansion of the universe that occur in the laboratory (as opposed to studying distant galaxies)," Schiller told Phys.org. "Our approach is one way to perform such a test. That we have not observed any effect is consistent with the prediction of general relativity."

Over the course of five months, the researchers made daily measurements of the resonator's length by measuring the frequency of an electromagnetic wave trapped within it. In order to suppress all thermal motion, the researchers operated the resonator at cryogenic temperature (1.5 degrees above absolute zero). In addition, external disturbances, such as tilt, irradiation by laser light, and some other effects that might destabilize the device were kept as small as possible.

To measure the resonator's frequency, the researchers used an atomic clock. Any change in frequency would indicate that the change in length of the resonator differs from the change in time measured by the .

The experiment detected virtually no change in frequency, or "zero drift"—more precisely, the mean fractional drift was measured to be about 10-20/second, corresponding to a decrease in length that the researchers describe as equivalent to depositing no more than one layer of molecules onto the mirrors of the resonator over a period of 3000 years. This drift is the smallest value measured so far for any resonator.

One of the most important implications of the null result is that it provides further support for the equivalence principle. Formulated by Einstein in the early 1900s, the is the idea that gravity and acceleration—such as the acceleration a person would feel in an upward-accelerating elevator in space—are equivalent.

This principle leads to several related concepts, one of which is local position invariance, which states that the non-gravitational laws of physics (for example, electromagnetism) are the same everywhere. In the current experiment, any amount of resonance drift would have violated local position invariance. Along similar lines, any amount of resonance drift would also have violated general relativity, since general relativity prohibits changes to the length of solid objects caused by the expansion of the universe.

Finally, the experiment also attempted to detect the hypothetical existence of spacetime foam. One of the effects of spacetime foam would be that repeated measurements of a length would produce fluctuating results. The constant measurement results reported here therefore indicate that such fluctuations, if they exist at all, must be very small.

In the future, the researchers hope that the extremely precise measurement technique using the cryogenic resonator could be used for other applications.

"One of the greatest outcomes of this work is that we have developed an approach to make and operate an that has extremely little drift," Schiller said. "This could have applications to the field of atomic clocks and precision measurements—for example, for the radar tracking of spacecraft in deep space."

Explore further: Test of equivalence principle searches for effects of spin-gravity coupling

More information: E. Wiens, A. Yu. Nevsky, and S. Schiller. "Resonator with Ultrahigh Length Stability as a Probe for Equivalence-Principle-Violating Physics." Physical Review Letters. DOI: 10.1103/PhysRevLett.117.271102. Also at arXiv:1612.01467 [gr-qc]

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21 comments

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xinhangshen
1 / 5 (8) Jan 05, 2017
Lisa Zyga, have you known that Einstein's relativity has been disproved both theoretically and experimentally (see "Challenge to the special theory of relativity" March 1 2016 Physics Essays)? The most obvious and indisputable experimental evidence disproving special relativity is the existence of the absolute time shown by the universally synchronized clocks on the GPS satellites which are moving with huge velocities relative to each other (see Wikipedia on GPS: The GPS concept is based on time and the known position of specialized satellites. The satellites carry very stable atomic clocks that are synchronized with one another and to ground clocks) while special relativity claims that time is relative (i.e. is different on different reference frame) and can never be synchronized on clocks with relative velocities.
rogerdallas
1 / 5 (2) Jan 05, 2017
Satellite velocities are negligible for purposes of measuring relativistic time dilation. Absolute time is not being measured and does not need to be measured, nor is the position of the satellites known with absolute accuracy-- it doesn't need to be. GPS measurements are good enough for all practical purposes, but not absolute. NOTHING is ever measured with absolute accuracy, ever.
rogerdallas
not rated yet Jan 05, 2017
Results like these tend to support the many-worlds interpretation of QM, if I am not mistaken. The many-worlds theory does not require any sort of space quantization.
shavera
4.3 / 5 (6) Jan 05, 2017
'Space quantization' is often a part of solutions trying to come up with a theory of QM that produces GR at large enough scales. 'Many worlds' is a philosophical concept trying to describe what might happen during a measurement of a QM system. They really aren't related in any way I'm familiar with.
shavera
4.6 / 5 (9) Jan 05, 2017
xinhangshen, your argument is not at all supported by actual data. The lifetimes of relativistically fast particles are lengthened by precisely the kind of relationship relativity predicts. Particle decay is very much a kind of clock, and as such, demonstrates that particles 'measure' time in a very different scale than the laboratory clock. Atomic clocks carried in planes got out of sync (but this is a convolved issue of both general relativity and special, since there's acceleration and changes in distance to a massive body).
Benni
1 / 5 (7) Jan 05, 2017
(but this is a convolved issue of both general relativity and special, since there's acceleration and changes in distance to a massive body).
.......this gibberish coming from a person who admits to having taken a "Thermodynamics For Beginner's" course in grad school. What was your major as an undergrad? Political Science? Journalism? C'mon Shavo, clue us in so we can better understand why you can never come across with a cogent thought in a science chatroom.

richdiggins
1 / 5 (1) Jan 05, 2017
"The only source of knowledge is experience." said one overrated theoretical physicist.
shavera
4.6 / 5 (11) Jan 05, 2017
Benni, what are you even on about? I've never had a textbook named "Thermodynamics for Beginners." I didn't have a thermodynamics course in grad school. And even attacking my credentials aside (which is silly anyway to trust anyone's 'credentials' on the interwebs), what I typed is a perfectly coherent physical statement. The issue (flying a clock) is an issue of General Relativity (height changes, acceleration) and Special Relativity (Lorentz boosted time-dilation from motion).
DonGateley
not rated yet Jan 06, 2017
Wow! No spacetime foam! That is huge and contradicts the theories of many scientists, starting with those at the Perimeter Institute.

I hope they are right. So many bad theories can be put to rest.

Wait, does that contradict Heisenberg?
fulely
1 / 5 (2) Jan 06, 2017
Everything is condensed photons! Time is light and dark energy! Astrophysics has been labeling the same object as different or unassociated but in fact are directly involved with each other. Nikola Tesla and aether or dark matter producing dark energy.
fulely
1 / 5 (1) Jan 06, 2017
Dark matter producing dark energy or light that created magnetism flows thru the magnetic fields of the universe
https://youtu.be/rENyyRwxpHo
xinhangshen
1 / 5 (4) Jan 06, 2017
xinhangshen, your argument is not at all supported by actual data.


How can you say that as my argument is just the fact that everybody knows:

The most obvious and indisputable experimental evidence disproving special relativity is the existence of the absolute time shown by the universally synchronized clocks on the GPS satellites which are moving with huge velocities relative to each other (see Wikipedia on GPS: The GPS concept is based on time and the known position of specialized satellites. The satellites carry very stable atomic clocks that are synchronized with one another and to ground clocks) while special relativity claims that time is relative (i.e. is different on different reference frame) and can never be synchronized on clocks with relative velocities.
shavera
5 / 5 (4) Jan 06, 2017
Suppose I have a watch that runs slow, not because of relativity, but just mechanically is slow. I can "synchronize" my watch with a more accurate clock every so often and the difference in time between my watch and 'real' time (on the other clock) isn't too bad. I'm pretty sure that's what they mean by 'synchronized' clocks on GPS satellites. The clocks definitely run at different rates than they would if they were stationary with respect to one another, or on the ground, but they can be kept in sync despite that limitation.

http://www.astron...gps.html

tells us that the clocks on GPS satellites run roughly 38 microseconds/day faster than a clock on the ground.
xinhangshen
1 / 5 (1) Jan 07, 2017
Suppose I have a watch that runs slow, not because of relativity, but just mechanically is slow. I can "synchronize" my watch with a more accurate clock every so often and the difference in time between my watch and 'real' time (on the other clock) isn't too bad. I'm pretty sure that's what they mean by 'synchronized' clocks on GPS satellites. The clocks definitely run at different rates than they would if they were stationary with respect to one another, or on the ground, but they can be kept in sync despite that limitation.

http://www.astron...gps.html

tells us that the clocks on GPS satellites run roughly 38 microseconds/day faster than a clock on the ground.


Yes, altitude, velocity and other factors may influence the frequency of a clock on the GPS satellites, but all these influences are absolute just like the one you have on your watch, which can be easily corrected to be synchronized with the standard clock.
shavera
5 / 5 (2) Jan 07, 2017
Yes, altitude, velocity and other factors may influence the frequency of a clock on the GPS satellites,


That's what's meant by time being measured at different rates from different observers.Except unlike the mechanical failure clock (slow spring, eg), all clocks in the same reference frame that measure the same time can be said to be 'accurate.' (Imagine you have 5 watches and only one 'runs slow', the other 4 are running 'on time.) When you compare these accurately running clocks to clocks in other frames, you will find that they disagree about the amount of time elapsed between certain events. (like the decay of a particle, for example)'
BackBurner
5 / 5 (3) Jan 08, 2017
Yes, altitude, velocity and other factors may influence the frequency of a clock on the GPS satellites, but all these influences are absolute just like the one you have on your watch, which can be easily corrected to be synchronized with the standard clock.


Shen, my guess is you're having difficulty with the words "synchronized" vs. "adjusted". The atomic clocks aboard GPS satellites aren't actually synchronized, they're adjusted for differences in relative velocities and altitudes and the need to do that is considered supportive of relativity theory, which predicts that such adjustments would be required. Rather than disproving GR, the GPS results support it.
Eddorian
5 / 5 (2) Jan 08, 2017
Also, one of the issues GPS systems deal with is the position with in the planetary gravity well. The deeper in the well, the higher the apparent acceleration experienced is, and thus the slower the clock should be.
xinhangshen
1 / 5 (5) Jan 09, 2017
Shen, my guess is you're having difficulty with the words "synchronized" vs. "adjusted". The atomic clocks aboard GPS satellites aren't actually synchronized, they're adjusted for differences in relative velocities and altitudes and the need to do that is considered supportive of relativity theory, which predicts that such adjustments would be required. Rather than disproving GR, the GPS results support it.


You just ignore the fact shown by Wikipedia on GPS: The GPS concept is based on time and the known position of specialized satellites. The satellites carry very stable atomic clocks that are synchronized with one another and to ground clocks.
xinhangshen
1 / 5 (6) Jan 09, 2017
Yes, altitude, velocity and other factors may influence the frequency of a clock on the GPS satellites,


That's what's meant by time being measured at different rates from different observers.Except unlike the mechanical failure clock (slow spring, eg), all clocks in the same reference frame that measure the same time can be said to be 'accurate.' (Imagine you have 5 watches and only one 'runs slow', the other 4 are running 'on time.) When you compare these accurately running clocks to clocks in other frames, you will find that they disagree about the amount of time elapsed between certain events. (like the decay of a particle, for example)'

Please don't use imagination, but use the fact (see Wikipedia on GPS: The GPS concept is based on time and the known position of specialized satellites. The satellites carry very stable atomic clocks that are synchronized with one another and to ground clocks).
nikola_milovic_378
not rated yet Feb 05, 2017
If we want to find out the cause of any phenomenon, we need to know how the universe was formed. The universe is infinite in diameter and is filled with substance in ether, and Nikola Tesla realized, but he never said he was the dark matter or dark energy. Nothing dark there, the only dark spot in the brain of those who do not understand the universe. Since ether is formed and all matter and all the energy of matter. Einstein's theory of relativity is a mirage, as the statement that the time and space "entangled" in a loving embrace, and when the masses enter into the "network" was the father of gravity. All the material -Energy entity was formed from the ether. With ether and matter (quarks, electrons and positrons), and energy (gluons) have an unbalanced condition that occurs when substances like gravity, and with gluons, as magnetism.
nikola_milovic_378
not rated yet Feb 05, 2017
All of it comes out.
Science has to give up Einstein and Lorentz misconceptions, if he wants to find out the true causes of the phenomenon. Also, an attempt to set up using atomic clocks existence of these mirage, is a failure and it shows that it knows how to work atom.

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