Probing the laws of gravity: A gravity resonance method

Apr 18, 2011
Neutrons between two plates in the earth's gravitational field can occupy different quantum states. A vibrating plate (below) can excite them from one state into the other - which allows extremely accurate energy mearurements.

Quantum mechanical methods can now be used to study gravity: At the Vienna University of Technology (TU Vienna), a measurement method was developed, which allows to test the fundamental theories of physics.

The world’s most precise measurement methods are based on . Atomic clocks or high-resolution magnetic resonance, which is used in medicine, rely on accurate measurements of quantum leaps: A particle excited at exactly the right frequency changes its quantum state – this is called “resonance spectroscopy”. Up until now, this method has only been used employing electromagnetic radiation. Researchers at TU Vienna have now developed a resonance method, which for the first time does not use electromagnetism, but the force of gravity. Gravity creates several possible quantum states for neutrons. The Gravity Resonance Method now allows to induce and accurately measure transitions between these states. The results of these experiments have now been published in the scientific journal Nature Physics.

At first glance, gravity and quantum physics do not appear to have much in common. We can feel gravity, when huge, heavy objects, such as stars or planets are involved. on the other hand are so light that gravity usually does not play a major role in describing them. The new method now links those two areas – now, the theory of gravity can be probed at minute distances. This way, scientists hope to gain insight into string theory or the nature of dark matter. So far, gravity research was limited to macroscopic or even astronomical distances.

Extremely Slow Neutrons

It is hard to measure the quantum physical effects of gravity at tiny length scales. “Atoms should better not be used for such experiments, because their behaviour is strongly influenced by short-range electromagnetic forces – such as the Van-der-Waals-force or the Casimir force”, professor Hartmut Abele form the TU Vienna explains. “But with our ultra-cold neturons, which are uncharged and hardly polarizable, we can do high-precision measurements at short distances.” Professor Abele carried out the experiments together with his assistants, Tobias Jenke and Dr. Hartmut Lemmel, and with Dr. Peter Geltenbort from the Institute Laue-Langevin in Grenoble.

Probing the laws of gravity: A gravity resonance method
Energy differences between quantum states have been measured for a long time, but the differences between quantum states which appear due to gravitation are a million millions smaller than the large energy gaps in atoms.

Quantum Leaps Between Gravity-States

We can lift up a stone to an arbitrary height – the higher we lift it, the more energy we have to spend. For quantum particles like neutrons, travelling between two horizontal plates, this is differerent: they can only take up discrete portions of gravitational energy. Using the neutron source of the Institute Laue-Langevin in Grenoble, the Vienna scientists managed to precisely define the quantum physical energy state of the neutrons between two plates. One of the plates was then vibrated at a precisely controlled frequency. If this frequency corresponds to the energy difference between two quantum states, the neutron is excited into the higher energy state. Measuring at which frequency this excitation takes places therefore reveals the exact energy difference between the quantum states.

Inertial mass and gravitational mass

Massive objects have two fundamental properties: They are inert (large forces are needed to accelerate them), and they are heavy (a strong gravitational force acts on them). Already in the 16. century, it was known that inertia and weight go together, and that this causes all objects to fall to the ground at the same speed. Whether this is only a good approximation, or whether this is also true at the minute length scales of quantum physics can now be investigated with the newly developed experiments.

For decades, physicists have been struggling to unify gravitation and quantum physics, creating a unified theory of everything. Different string theories have been developed, predicting the existence of hidden spatial dimensions, which have not yet been discovered. “Using our neutron method, we will try to test such theories in the laboratory”, professor Hartmut Abele announces. Even for cosmology, these experiments may play an important role. Theories about the mysterious “dark matter”, which is considered to govern the motion of galaxies, could now be investigated on tiny scales with high-precision measurements. “Our method, which is specially designed for minute length scales, could – if we are lucky – help us understand the evolution of the universe itself. In any case, thrilling new insights in research are awaiting us”, says professor Abele.

Explore further: Thermoelectric power plants could offer economically competitive renewable energy

Provided by Vienna University of Technology

4.5 /5 (18 votes)

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User comments : 21

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Nik_2213
not rated yet Apr 18, 2011
This is an astonishing technical feat ! A question: does the vibrating plate emit gravitons, or is this a different phenomenon ??
TabulaMentis
not rated yet Apr 18, 2011
This is an astonishing technical feat ! A question: does the vibrating plate emit gravitons, or is this a different phenomenon ??
The article does not mention anything about gravitons. This machine is a lot smaller and less expensive than the LIGO.

http://(omit)ligo.caltech.edu/#
jscroft
5 / 5 (4) Apr 18, 2011
If gravitons exist, and if the vibrating plate has mass, then it would emit gravitons. So would YOU, by the way. In any case, I imagine that the first steps here are not to detect the graviton, but simply to test whether macro-scale gravitational models hold on the scale of a neutron.

Whether they do or not, these fellows may very well be looking at a Nobel Prize before long.
Shootist
3.7 / 5 (3) Apr 18, 2011
"In any case, thrilling new insights in gravity research are awaiting us, says professor Abele"

Faster please.
Paljor
not rated yet Apr 18, 2011
how do they counteract the force of our own gravity i wonder?
ZephirAWT
Apr 18, 2011
This comment has been removed by a moderator.
Moebius
4.7 / 5 (13) Apr 18, 2011
It's just another example of senile useless re-search. As an evidence of extradimensions can serve notoriously known Casimir force or every Van der Waals and/or dipole force, which are violating the inverse square law at short distances. We cannot find another source of gravity violation with slow neutrons, if we didn't detected it with way more massive bodies at the same distance. Such research should be subject of public feedback first.


What are you, a luddite? Considering how much money we spend on physics experiments, this one is probably bargain basement cost and might just find new science.
beelize54
1.8 / 5 (11) Apr 18, 2011
There were many searches of extradimensions already. Indeed, the search for gravitational waves, WIMPs or Higgs boson is the waste of the public money in the same category. Whereas the cold fusion, antigravity or room temperature superconductivity findings are ignored for years...

Does it appear as a normal situation in science for you?
Husky
5 / 5 (2) Apr 18, 2011
theres been a lot of heated discussion on this board lately about the antimatter/antigravity(?) article.

Due to its small available amounts, this experiment possibly makes it testible.
Husky
5 / 5 (3) Apr 18, 2011
theres been a lot of heated discussion on this board lately about the antimatter/antigravity(?) article.

Due to small availabillity of antimatter, this experiment would make it testible at the miniscule quantum level.

Getting a sizeable and managable stream of antineutrons is still a bit of a challenge, but I think it would be possible if much effort was put into it.
kaasinees
3.7 / 5 (3) Apr 18, 2011
Wow this is a breakthrough in physics... making our very fundation of pyhsics testable...
unknownorgin
not rated yet Apr 19, 2011
There is like putting a mass on a spring , some frequency it will resonate up and down. Every object has its own gravitational field so a neutron between the plates is pulled by both plates equaly until the vibrating plate moves closer to the neutron and pulls harder or away and pulls less so at some frequency it will resonate like a bell but if the inertia of the neutron changes with energy levels how can you define atomic weights? also what happens with hydrogen (a proton)?
dogbert
5 / 5 (2) Apr 19, 2011
This is exciting. We need a better understanding of the nature of gravity. This looks like a promising development to expand our understanding.
OdieNewton
5 / 5 (1) Apr 19, 2011
This is absolutely fantastic, within the next few decades we might see a definitive model of gravity! That stuff makes history.

And for those who say "Oh this is such a waste of time and money," remember that things like a heliocentric orbit and electricity also seemed pretty dumb back in the time of their discovery. Nothing ventured, nothing gained!
Aristoteles
not rated yet Apr 19, 2011
Extremely accurate energy mearurements produce extremely dis-accurate space-time position mearurement...
THERE IS BIG NEED IN extremely accurate i n t e r p r e t a t i o n and accurate philosophy ( pure of UFO-
inpurity...).
El_Nose
5 / 5 (2) Apr 20, 2011
There were many searches of extradimensions already. Indeed, the search for gravitational waves, WIMPs or Higgs boson is the waste of the public money in the same category. Whereas the cold fusion, antigravity or room temperature superconductivity findings are ignored for years...


well cold fusion and antigravity have no basis -- in fact name one experiment where it has worked -- and the energy catalyzer is still subject to debate ---

but superconductivity is highly funded and high temp superconductors now reach as high as 17 C

But you argue that the question he have the biggest reason to believe in are over funded --- indeed the reason we believe in dark matter is because it is a logical answer to an equation that has stoood the test of time and more and more measurements -- and BTW the search for WIMPS and DM is essentially the same thing with two different approaches -- and the search for the Higgs might answer questions we can even think to ask yet.
ZephirAWT
Apr 21, 2011
This comment has been removed by a moderator.
ZephirAWT
Apr 21, 2011
This comment has been removed by a moderator.
jscroft
5 / 5 (1) Apr 21, 2011
@El Nose: 17C? Holy cow, when did THAT happen? Do you have a link?
georgert
5 / 5 (3) Apr 23, 2011
There were many searches of extradimensions already. Indeed, the search for gravitational waves, WIMPs or Higgs boson is the waste of the public money in the same category. Whereas the cold fusion, antigravity or room temperature superconductivity findings are ignored for years...

Does it appear as a normal situation in science for you?


Yes, it does appear normal. Deeper research into areas of physics that have proven to be coherent descriptions of nature promise greater dividends than equivalent funding on projects that have no sound theoretical basis, e.g., telepathy, UFOs, superluminal transport, cold fusion, walking on water, pixies... etc.
PinkElephant
not rated yet Apr 24, 2011
Could someone who knows quantum mechanics better than me, please explain why being located between two plates somehow makes a difference to the quantum state of a neutron? It's not affected electrostatically by the proximity of those plates, so what is the fundamental difference in the neutron's configuration of being between plates vs. being in a vacuum?

Furthermore, how does a plate (regardless of whether it's vibrating or not) interact with a free-falling ultra-cold neutron?
For quantum particles like neutrons, travelling between two horizontal plates, this is differerent: they can only take up discrete portions of gravitational energy.
Really? That would seem to violate General Relativity in all kinds of ways... unless (and probably because) there's something I don't understand about the interactions between the plates and the neutron (as opposed to between the neutron and gravity.)
beelize54
Apr 24, 2011
This comment has been removed by a moderator.
beelize54
1 / 5 (2) Apr 24, 2011
The undulating water surface analogy describes this phenomena well, as it was demonstrated before some time in Couder's experiments with double slit.

http://www.physor...511.html

You may think, the undulating water surface has always a larger surface area, then this calm one, so it slows down the particle spreading on it accordingly. At the proximity of barrier the water surface creates the standing interference wave, so its deformation becomes a predictable function of the distance from the barrier. Heavier particles would make the water surface undulate faster with higher frequency, so that their slowing will be apparent closer from the barrier. We could therefore detect the gravity changes at the close proximity of barrier.

But these experiments are naive in their attempts to detect the presence of extradimensions and to eliminate the Casimir force at the same moment - because the Casimir force is just one of manifestations of extradimensions.
beelize54
1 / 5 (2) Apr 24, 2011
There is interesting aspects of experiments, who are seeking for extradimensions with violation of gravitational law at short distances, because they're systematically arranged in such way, these extradimensions cannot be found. Because in every experiment theorists carefully removed/compensated the presence of all effects, which could interfere the gravity, we could call them a string theory diversionists (wreckers) - despite they're all trying to find the extradimensions strenuously ...;-)

This approach is only partially incomprehensible for external observer of this effort, because scientific community has not only motivation in new findings - it has an apparent motivation in continuity of its research, which actually violates the possibility of new findings: when we find something, the research ends. So we should understand the history of extradimensions research in wider socio-psychological context.
MaxwellsDemon
5 / 5 (2) Apr 24, 2011
@PinkElephant
what is the fundamental difference in the neutron's configuration of being between plates vs. being in a vacuum?


Think of the space between the two plates as a quantum waveguide. The extremely cold neutrons pass through a space which is minute enough to physically suppress the wavefunction of the neutrons to one of only two energy modes (which are induced by the gravitational field gradient acting upon them). This way, the plates and the neutrons are coupled. Then, when one plate oscillates at the proper excitation frequency between the two neutron energy modes, some of its energy may be transferred to the neutrons, in a way that's analogous to electromagnetic evanescent wave coupling.

It's not entirely dissimilar to how vacuum fluctuation modes are restricted between two plates in the Casimir effect, except in this case the relevant waves are those of the cold neutrons, rather than ambient virtual particles.

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