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Using Neutrons To Precisely Test Newton's Law of Gravity

Soulskill posted more than 3 years ago | from the attempting-the-full-isaac dept.

Science 123

NotSanguine writes with this excerpt from the BBC: "The neutrons are shot between two parallel plates, one above another and separated by about 25 micrometres — half a hair's width. The upper plate absorbs neutrons, and the lower plate reflects them. As they pass through, they trace out an arc, just like a thrown ball falling due to gravity. ... The new work by the ILL team has added what is known as a piezoelectric resonator to the bottom plate; its purpose is to jiggle the bottom plate at a very particular frequency. The researchers found that as they changed the bottom plate's vibration frequency, there were distinct dips in the number of neutrons detected outside the plates — particular, well-spaced 'resonant' frequencies that the neutrons were inclined to absorb. These frequencies, then, are the gravitational quantum states of neutrons, essentially having energy bounced into them by the bottom plate, and the researchers were able for the first time to force the neutrons from one quantum state to another. The differences in the frequencies — which are proportional to energy — of each of these transitions will be an incredibly sensitive test of gravity at the microscopic scale."

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Newton's (1, Informative)

Dr. Spork (142693) | more than 3 years ago | (#35861640)

Wow, my physics courses apparently forgot to mention that Newton's Law of Gravity had anything to say about the quantum states of neutrons. In fact, I was taught it's not a law; it's a falsified hypothesis.

Re:Newton's (5, Informative)

catchblue22 (1004569) | more than 3 years ago | (#35861780)

Wow, my physics courses apparently forgot to mention that Newton's Law of Gravity had anything to say about the quantum states of neutrons. In fact, I was taught it's not a law; it's a falsified hypothesis.

Newton's Law of Gravity can be seen as an approximation of Einstein's theory. We have to be careful when we speak of "falsified". We haven't discovered that gravity is proportional to 1/r, or that gravity isn't attractive but repulsive. We have discovered that Einstein's models are better predictors of experimental results. We can still us Newton's models to send humans to the Moon. But Newton's model makes no sense when asking questions such as "what would happen to the Earth if the Sun suddenly disappeared. It doesn't predict the bending of light, nor does it properly describe certain orbital phenomenon.

Re:Newton's (2)

catchblue22 (1004569) | more than 3 years ago | (#35861964)

It doesn't predict the bending of light

Err...sorry. I should have said it doesn't predict the bending of light in gravitational fields.

Re:Newton's (3, Interesting)

SoVeryTired (967875) | more than 3 years ago | (#35862102)

Actually it does, but by half the amount predicted by general relativity. This was known to Cavendish in the late eighteenth century.

http://en.wikipedia.org/wiki/Tests_of_general_relativity#Deflection_of_light_by_the_Sun [wikipedia.org]

Re:Newton's (1)

blair1q (305137) | more than 3 years ago | (#35862878)

How did Newton give light mass?

Or did he somehow grok that space itself is warped by mass?

Re:Newton's (4, Informative)

femtobyte (710429) | more than 3 years ago | (#35863154)

You don't need to know what the mass of light is, you only need to treat it as a classical particle traveling at 3e8 m/s. From classical mechanics, objects follow the same trajectory in a gravitational field regardless of mass (different orbits depend only on different initial positions/velocities); a beam of light can be treated just like a very fast moving comet. The mass of the light would only be important if you were trying to calculate the reverse effect of how much a passing light beam would move a planet/star as it passed. The fact that light travels at a finite speed has been known for a long time.

Re:Newton's (1)

Roger W Moore (538166) | more than 3 years ago | (#35864750)

You don't need to know what the mass of light is...

Actually you do because if the mass is zero there is no force according to Newton's law of gravity and hence no deflection. Cavendish did not know this in 1804.

Re:Newton's (2, Interesting)

Anonymous Coward | more than 3 years ago | (#35865244)

Zeroes are troublesome in physics. If a light particle has zero mass, it would mean that any force at all would cause an infinite acceleration. Since it was known that light travelled at finite speeds, it's reasonable to assume that light particles did have a mass (of course, classically there's no such thing as rest mass)

Re:Newton's (-1)

Anonymous Coward | more than 3 years ago | (#35865324)

The photon has no rest mass.

Re:Newton's (3, Interesting)

pclminion (145572) | more than 3 years ago | (#35863406)

Two things. First: Newton knew that all objects (at least, all objects we've tested) accelerate toward the earth with a certain acceleration regardless of mass, depending only on their distance from the earth. If the law of gravitation is universal, then why wouldn't light also experience the same acceleration? Assuming that massless particles are an exception goes against Occam's Razor. Only if we observe that light does not deflect would we conclude our theory was wrong. Newton was unable to perform this experiment.

Second: Why would Newton automatically assume that light did not have mass? It seems perfectly obvious today, but is it obvious because everyone knows it or because it's obvious? I don't think it's obvious.

Re:Newton's (1)

Roger W Moore (538166) | more than 3 years ago | (#35864788)

Two things: First the question is what deflection does Newton's law of gravity predict for the deflection of light, not did Newton know that light was massless.

Two: Newton and Cavendish did not know that light was massless but we do and so Newton's law predicts no deflection i.e. Cavendish got it wrong but so would anyone else predicting the behaviour of a particle which was discovered about 100 years after he wrote his paper!

Re:Newton's (3, Informative)

Woek (161635) | more than 3 years ago | (#35865372)

Photons have mass, because they have energy. Furthermore, that photons have zero rest mass is still only an assumption in most models (ref [ucr.edu] )

Re:Newton's (1)

blair1q (305137) | more than 3 years ago | (#35870250)

Most models accept the data that say that photons are never at rest.

Re:Newton's (1)

pclminion (145572) | more than 3 years ago | (#35868520)

First the question is what deflection does Newton's law of gravity predict for the deflection of light, not did Newton know that light was massless.

No. The question was "How did Newton give light mass? Or did he somehow grok that space itself is warped by mass?" See parent of my post.

It does NOT! (1)

Roger W Moore (538166) | more than 3 years ago | (#35864736)

Actually it does, but by half the amount predicted by general relativity.

Actually it does NOT. Cavendish made suppositions without any clue to what light was - the date on Cavendish's paper was 1804, well before even Maxwell's equations let alone photons were known. Having no clue about light they supposed that it would follow a trajectory as any massive body does - quite reasonable not given any evidence to the contrary - but now we know better!

Newton's statement of his law explicitly states that the attraction is proportional to the masses of the bodies and, since a photon has no mass, there is no attractive force. So the prediction for light, composed of massless photons, is no deflection. Relying on Wikipedia articles quoting 19th century physics papers attempting to describing the behaviour of particles we discovered in the early 20th century is unlikely to be reliable!

Re:It does NOT! (2)

Celarent Darii (1561999) | more than 3 years ago | (#35865498)

Firstly you are wrong in saying that a photon has no mass. It has no rest mass, but it certainly has energy, and even momentum (hv/c). Force is not just m*a, but even more correctly described as the change of momentum dp/dt. Gravity is a force and therefore it causes a change of momentum.

There are many papers that speculate that is light is a particular, what must be the effect of gravity upon it, dating from several years before Cavendish even.

Here is a citation of a letter from John Michell, 1783, even predicting what we call black holes today:

http://books.google.pl/books?id=XpyvPTRwLoQC&pg=PA368&lpg=PA368&dq=Cavendish's+paper+on+gravity+and+light&source=bl&ots=EXGBWCHeYy&sig=g4vE442GKMsAtLsa0yH5ehiUIh8&hl=pl&ei=UEStTf2TGoPxsgaZ1c3XDA&sa=X&oi=book_result&ct=result&resnum=3&ved=0CCsQ6AEwAg#v=onepage&q=light%20gravity&f=false

The idea of photons, even if the name is recent in origin, is as old as light itself. Even Aristotle tried to reconcile several theories of light as being a "streaming substance" (a substance carrying some sort of energy, see de Anima), or as a "ray". The observation of motion of dust particules in a sunlight room does not date from last century.

The more you read the works of the ancient physicists, you will discover that they certainly were not people "without any clue", but often trying to wrap their minds around some serious observations. Whether they succeeded or not is another question, but they certainly had some clue.

Re:Newton's (1)

bcrowell (177657) | more than 3 years ago | (#35862376)

I agree with the basic thrust of your post, but have one nitpick to make:

But Newton's model makes no sense when asking questions such as "what would happen to the Earth if the Sun suddenly disappeared.

Actually, general relativity doesn't answer this either, because GR has local conservation of mass-energy, so it doesn't allow the sun to disappear. A better example would be "What would happen to the Earth if the Sun suddenly zoomed away from us at nearly the speed of light." Admittedly I'm being totally pedantic here.

Re:Newton's (1)

Adult film producer (866485) | more than 3 years ago | (#35862676)

so... what would happen ?

Re:Newton's (2)

nedlohs (1335013) | more than 3 years ago | (#35862858)

The energy required to make it happen would kill us all probably by turning all the inner rocky planets to molten balls of slag.

Re:Newton's (1)

ShakaUVM (157947) | more than 3 years ago | (#35864814)

>>We haven't discovered that gravity is proportional to 1/r, or that gravity isn't attractive but repulsive.

Err, gravity *can* be repulsive.

Re:Newton's (0)

Anonymous Coward | more than 3 years ago | (#35867304)

>>We haven't discovered that gravity is proportional to 1/r, or that gravity isn't attractive but repulsive.

Err, gravity *can* be repulsive.

Agreed. Fat chicks have more gravity and are more repulsive

Re:Newton's (2)

Nivag064 (904744) | more than 3 years ago | (#35865690)

[...]

But Newton's model makes no sense when asking questions such as "what would happen to the Earth if the Sun suddenly disappeared. It doesn't predict the bending of light, nor does it properly describe certain orbital phenomenon.

Actually, Newton's Gravitational laws _DID_ predict the bending of light by the Sun, but by a different amount!

There is a factor of 2 difference (can't remember which predicted the greater bending!).

Re:Newton's (1)

Dabido (802599) | more than 3 years ago | (#35866238)

But Newton's model makes no sense when asking questions such as "what would happen to the Earth if the Sun suddenly disappeared.

Don't worry, I'm on that one. "It would get very dark." There, no need to worry about that now!

Re:Newton's (0)

Anonymous Coward | more than 3 years ago | (#35870410)

What would happen to the Earth if the sun suddenly disappeared?

Re:Newton's (1)

Hope Thelps (322083) | more than 3 years ago | (#35861784)

In fact, I was taught it's not a law; it's a falsified hypothesis.

Tell it to the judge.

Re:Newton's (1)

dch24 (904899) | more than 3 years ago | (#35861800)

This is news to me too. In the BBC article [bbc.co.uk] , it says gravitational quantum states were only measured in 2002, in the parent experiment (the one where they didn't use piezo resonators -- just parallel plates).

Cool! Falsifiable experiments testing unified theories, like string theory!

Re:Newton's (5, Informative)

pclminion (145572) | more than 3 years ago | (#35861804)

If you bother to read the article, you see that they are trying to see whether good old Newtonian gravity is a good approximation at extremely small length and mass scales (scales where the additional accuracy provided by general relativity is unnecessary). They're trying to see if when you make the experiment this sensitive, do you see some kind of quantum effect. The answer so far seems to be no. Yes, the neutrons behave in a quantum mechanical way. The question is, do they behave as you'd predict if Newton's/Einstein's gravity is true, or do they do something unexpected? This has nothing to do with Newton vs. Einstein.

Re:Newton's (1)

BlueParrot (965239) | more than 3 years ago | (#35865876)

If you bother to read the article

Ahhhh. I love the smell of slahsdot in the morning.

Re:Newton's (4, Interesting)

jd (1658) | more than 3 years ago | (#35861830)

I disagree with the claim that it is falsified. All theories in physics come with two sets of conditions: the bounds in magnitude and the bounds in resolution. Newton's theory came with well-defined bounds - those of classical phenomena. You cannot extrapolate beyond those bounds and claim you are still working with the theory because the theory isn't defined beyond those bounds. Nor can you interpolate to the quantum level for the same reason - the theory isn't defined there.

Relativity didn't replace Newton's theory, it supplemented it. In computing terms, it's a third-party module you can add on. When you install the Relativity dynamic library, the combined theory applies to a much larger range of phenomena.

The only time a theory will actually be falsified is if QM's gravity or relativity can be patched to work within the other's range. They are contradictory and you cannot load both modules into Newtonian physics at the same time. Only one of these two will stand the test of time, the other will die. Whichever one wins will then merge with Newtonian mechanics to produce a universal law of gravity.

Re:Newton's (2)

lennier (44736) | more than 3 years ago | (#35863224)

Newton's theory came with well-defined bounds - those of classical phenomena.

I'm not sure that's correct. In Newton's time the word "classical" in the sense of either non-relativistic or non-quantum didn't exist. Gravity and the other mechanical forces are continuous and space is three-dimensional with independent time dimension in Newton's model. The entire idea of "bounds" in terms of relative speed and size where Newtonian mechanics don't apply was invented much later (both pretty much by Einstein) and would likely have seemed ridiculous to Newton.

The interesting thing is that Einstein's two brainchildren - quantised photons and general relativity - don't play well together.

Re:Newton's (2)

jd (1658) | more than 3 years ago | (#35865206)

The idea of physical theories being bounded was actually quite popular in Newton's time - hence the phrasing of Hooke's Law, the approximation of the motion of pendulums, etc. The laws were all quite specifically written in the form "provided these preconditions are true, this result WILL apply". Newton didn't change this in the slightest.

Indeed, that should be obvious from the description of gravitational attraction. Object X is pulled towards object Y because of the mass of object Y alone. However, it is equally true, by the same law, that object Y is pulled towards object X because of object X's mass. They are both pulled towards a common point. Newton was quite aware of this. If you jump up, you do not fall to the Earth, both you and the Earth move towards a common point. Because your mass is insignificant compared to that of the Earth (well, depending on how addicted you are to fast food), you can treat the Earth as in effect a stationary object.

Thus, although Newton's laws require you to apply the laws in both directions to get the "exact" result of his theory, you won't ever find that done in practice. By the time you get to objects of comparable size that can orbit each other you have to start factoring in relativity anyway. Even Newton never really considered the common center of gravity - he expressly confined himself to objects of significantly different mass such that the common center of mass is approximately the same as the center of mass of the larger object. There was never any attempt by Newton to extrapolate outside of that boundary.

There was an unwritten limitation also imposed on it. The addition law of vectors had to apply. This was a geometric property and there were certainly geometries known at the time in which the addition law did NOT hold. Thus, Newtonian Mechanics has the implicit precondition that you are working in a valid geometry. All QM and GR/SR geometries are invalid EXCEPT for special cases when both these theories reduce quite nicely to classical Newtonian Mechanics.

Re:Newton's (1)

JamesP (688957) | more than 3 years ago | (#35863358)

Exactly. There's no need to go to relativity for most of the cases.

But everyone that thinks otherwise is welcome to calculate sqrt(1 - v^2/c^2) for their experiment's velocity and see if the values vary significantly

ATLAS/LHC (1)

Roger W Moore (538166) | more than 3 years ago | (#35864836)

But everyone that thinks otherwise is welcome to calculate sqrt(1 - v^2/c^2) for their experiment's velocity and see if the values vary significantly

I'm not sure that works too well - my experiment [atlas.ch] is large and very stationary but the particles we collide in the middle have a gamma [which is 1/sqrt(1 - v^2/c^2)] of well over 3,500.

Re:ATLAS/LHC (1)

jd (1658) | more than 3 years ago | (#35865110)

I think it's fair to consider the relativistic velocity* of the particles as being the key part of the experiment for ATLAS (much as it was for EUROGAM, the one I worked on). However, even if you consider the relativistic velocity of the detectors, it would be relative to the byproducts of the collision and not to the observing scientist. Thus, the velocity of the experiment is still not zero -- except in summation. (Although the relativistic velocity is very high, the resultant velocity is nearly zero.)

*In relativity, it is prohibited for any particle to observe another particle moving faster than C. In order for this to be true when a central observer sees two particles each closing in at near-C from opposite directions, you have to assume that you cannot simply sum up the velocities. You have to divide by 1 + vu/(c^2).

Re:ATLAS/LHC (1)

JamesP (688957) | more than 3 years ago | (#35866132)

Well, I've heard about your experiment, and it's actually pretty fast, going at around 30 km/s around a large mass of hydrogen currently undergoing fusion! ;)

Re:Newton's (3, Interesting)

Raenex (947668) | more than 3 years ago | (#35864258)

This is a terrible apology for Newton's theory of gravity. Einstein's relativity isn't an "add on" module. It completely subsumes Newton's theory, and shows that is just a very good approximation at ordinary scales.

This in no way diminishes Newton's accomplishment, or even usefulness. However, we can say that his theory of gravity has been falsified.

Re:Newton's (1)

FrootLoops (1817694) | more than 3 years ago | (#35864346)

There's a big difference between today's conception of Newtonian mechanics and (what I presume was) the original conception of it. Today, we call it an approximation; originally, it was perfectly precise. The original idea has been falsified, but the newer version with supplemental error bounds is alive and well. The add on analogy is a little bit of a stretch, but I don't think it's awful. Loading the GR module would be akin to adding routines that could predict the impact of a black hole meandering through our solar system, for instance, in addition to improving the accuracy of the Newton module's routines. It entirely replaces the Newton module, which is where the stretch comes in. Quantum fits pretty well in the analogy, though.

Kernel Upgrade? (1)

Roger W Moore (538166) | more than 3 years ago | (#35864872)

Perhaps a kernel upgrade would be a better analogy for slashdot? The core of the system has had a major improvement but the desktop GUI is not really affected. So, unless you are a kernel hacker/gravitational physicist there are not many noticeable changes!

Re:Newton's (1)

jd (1658) | more than 3 years ago | (#35865136)

I'm not sure that you can say that it replaces the theory. You can use Newtonian mechanics exactly as Newton wrote them, without changing them one iota, but merely pass in the relativistic values rather than the classical ones. That doesn't sound like a replacement, that's a pre-processing routine at best. Gallilean addition of velocities is then modified by dividing the original result with a new result. A post-processing module.

In relativity, light still travels along straight lines but along a warped topology. The result is the appearance of light being bent by gravity, when it is space that is bent. Light is unaffected.

Where is the replacement?

Re:Newton's (1)

tyrione (134248) | more than 3 years ago | (#35865404)

I'm not sure that you can say that it replaces the theory. You can use Newtonian mechanics exactly as Newton wrote them, without changing them one iota, but merely pass in the relativistic values rather than the classical ones. That doesn't sound like a replacement, that's a pre-processing routine at best. Gallilean addition of velocities is then modified by dividing the original result with a new result. A post-processing module.

In relativity, light still travels along straight lines but along a warped topology. The result is the appearance of light being bent by gravity, when it is space that is bent. Light is unaffected.

Where is the replacement?

Agreed and I will add that in 20 years or so we'll have new additions to Physics that augments Relativity and the exactness of what is actually going on with Force in a system will have a more complete picture, but we don't spit on the foundation of Newton and Einstein--we'll augment them.

Re:Newton's (1)

FrootLoops (1817694) | more than 3 years ago | (#35869642)

That's a bit of an oversimplification of relativity. Some simple, highly idealized calculations can be done by just replacing an input with a modified version of it, or modifying the result of a Newtonian calculation. But, calculations involving significant gravity are far more complex. I would agree with you if we were talking about special relativity instead of general, or if the calculations were kept simple.

Re:Newton's (0)

Anonymous Coward | more than 3 years ago | (#35867364)

Newtons theory includes an axiomatic treatment of time. To quite the great man himself: "Absolute, true and mathematical time, of itself, and from its own nature flows equably without regard to anything external.." We believe this statement to be false today

Re:Newton's (1)

Anonymous Coward | more than 3 years ago | (#35864362)

Great... Just what I need...

A Relatavistic DLL Hell....

Re:Newton's (1)

jd (1658) | more than 3 years ago | (#35865140)

Just wait for Physics 3.0 - The Quantum DLLs can be both installed and not installed at the same time.

Re:Newton's (1)

tyrione (134248) | more than 3 years ago | (#35865396)

Correct! It makes me wonder if the Dr. originally posting his crap has the background to even comprehend basic Classical Mechanics.

Re:Newton's (0)

Anonymous Coward | more than 3 years ago | (#35867202)

Perhaps both theories need to be modified or patched if you prefer.

Re:Newton's (2)

pablomme (1270790) | more than 3 years ago | (#35861848)

I thought the same when I read this piece of news yesterday. Journalists like to fill their sentences with words that sound appropriate to them: "[Newton's Law of] Gravity", "8.1 magnitude [in Richter's scale]"... and often they make mistakes.

Re:Newton's (0)

Anonymous Coward | more than 3 years ago | (#35866252)

Wow, my physics courses apparently forgot to mention that Newton's Law of Gravity had anything to say about the quantum states of neutrons. In fact, I was taught it's not a law; it's a falsified hypothesis.

Here's what the actual paper's summary says (I'm not logging in or paying to read the full research paper)

The experiments have the potential to test the equivalence principle[3] and Newton’s gravity law at the micrometre scale[4], [5].

Re:Newton's (0)

Anonymous Coward | more than 3 years ago | (#35869306)

Wow, my physics courses apparently forgot to mention that Newton's Law of Gravity had anything to say about the quantum states of neutrons. In fact, I was taught it's not a law; it's a falsified hypothesis.

The world class researchers doing this study also took a freshman physics course. And several more beyond that... and several more beyond that... and several more beyond that. Consider the possibility that they know more than you about the subject of gravity.

Assuming they weren't testing a plate resonance (1)

Ungrounded Lightning (62228) | more than 3 years ago | (#35861678)

I hope they took into account the possibility that they were exciting a mechanical resonance of the plate, which would cause it to vibrate and as a result occasionally be positioned differently and possibly intercept the neutrons at slightly higher or lower locations, corresponding to higher or lower energy.

Resonant modes of the plate would also be a function of frequency.

Re:Assuming they weren't testing a plate resonance (2)

blair1q (305137) | more than 3 years ago | (#35861922)

According to the second link, the resonance was at about 705 Hz.

The plate would have to be fairly wide and floppy to resonate at that frequency, but then it wouldn't have much gravitational attraction, so the plate is probably thick and chunky, and not very flexible. And it would have to be made of rubber to have any body resonance at that frequency.

Re:Assuming they weren't testing a plate resonance (0)

Anonymous Coward | more than 3 years ago | (#35864504)

They aren't measuring gravitational attraction towards the plate, they're measuring 1D bound states for a quantum object experiencing constant acceleration against an impenetrable barrier (the mirror). Imagine the infinite square well except the well area has a tilt.

By vibrating the mirror at frequencies corresponding to the energy difference between bound states, they can make the neutrons change state / "move up and down" while they're confined by earth's gravitational potential - thereby testing precisely the interaction of that potential with matter at the subatomic level.

Re:Assuming they weren't testing a plate resonance (5, Funny)

femtobyte (710429) | more than 3 years ago | (#35862120)

Yes, we obviously need to be worried that the large team of scientists and engineers who designed and built this experiment have overlooked the most basic principles of freshman physics and mechanical design. Good thing we have the keen intelligence of Slashdot science critics to catch all these subtle flaws that would otherwise slip by the reviewers at Nature un-noticed. Should we also worry that the scientists are all part of the government conspiracy to cover up the true Time Cube four-side harmony perfection of gravity symmetry?

Re:Assuming they weren't testing a plate resonance (1)

T-Bone-T (1048702) | more than 3 years ago | (#35864542)

A Martian probe was destroyed by a mixup of SI and Imperial units so it seems safe to say they may have overlooked something basic.

Re:Assuming they weren't testing a plate resonance (1)

solarlux (610904) | more than 3 years ago | (#35868166)

To be more specific, a Martian probe was destroyed because incompatible legacy software was used and the integration of it was not tested appropriately due to "faster, cheaper, better" funding cuts...

sheilding for spacecraft? (0)

Anonymous Coward | more than 3 years ago | (#35861716)

Is this an avenue for researching into spacecraft shielding?

this is wrong (4, Funny)

circletimessquare (444983) | more than 3 years ago | (#35861756)

the bible doesn't talk about neutrons

Re:this is wrong (1, Interesting)

Anonymous Coward | more than 3 years ago | (#35862066)

the bible doesn't talk about neutrons

You're holding it wrong.

Re:this is wrong (0)

blair1q (305137) | more than 3 years ago | (#35862096)

If it doesn't talk about Metatrons, it's sure not going to go there.

Re:this is wrong (1)

140Mandak262Jamuna (970587) | more than 3 years ago | (#35862284)

Come on. Bible does not talk about American Exceptionalism, nor our inherent right to bomb any nation into oblivion, not even why He buried our oil under their sand. Still we know these are all true.

Re:this is wrong (3, Funny)

Anonymous Coward | more than 3 years ago | (#35862366)

That oil isn't under their sand... it's way, way, way under American soil. Drilling there is merely a shortcut.

Re:this is wrong (0)

Anonymous Coward | more than 3 years ago | (#35866352)

Bible does not talk about American Exceptionalism

Sure it does, we're the "New Rome".

nor our inherent right to bomb any nation into oblivion

Two words- "Manifest Destiny".
And you might want to try reading the book, most of it is about God telling his people to go commit Genocide, or at least pillage, conquer, and enslave.

He buried our oil under their sand

You're right, it doesn't tell us anything at all about oil. In fact, the only oil mentioned is olive oil. The logical conclusion is that just like fossils, and Women's Suffrage, oil was created by The Devil to Tempt God's Chosen People into Sin.

Still we know these are all true.

Might makes right, he with the most Gold makes the Rules, etc. If you don't want to believe that you're either an idiot or incomprehensibly naive.

Re:this is wrong (1)

Culture20 (968837) | more than 3 years ago | (#35862644)

It doesn't talk about gravity either.
Although regarding neutrons, some people speculate that the Ark of the Covenant was radioactive since plagues of tumors followed it. [biblegateway.com] and people who looked into it quickly died. [biblegateway.com]

Re:this is wrong (4, Funny)

Black Parrot (19622) | more than 3 years ago | (#35862940)

Although regarding neutrons, some people speculate that the Ark of the Covenant was radioactive since plagues of tumors followed it. [biblegateway.com] and people who looked into it quickly died. [biblegateway.com]

Raiders of the Lost Ark explained it better, and without appealing to hocus-pocus such as gravity and radioactivity.

Re:this is wrong (1)

Black Parrot (19622) | more than 3 years ago | (#35862912)

the bible doesn't talk about neutrons

Try searching with the Bible Codes program.

Re:this is wrong (0)

Anonymous Coward | more than 3 years ago | (#35864320)

F***ing neutrons, how do they work?

------RM

Gravitational quantum states of neutrons, eh? (0)

Anonymous Coward | more than 3 years ago | (#35861760)

These frequencies, then, are the gravitational quantum states of neutrons

Okay, who knows what this means, who can explain it in a way that leaves the rest of us thinking we sort of understand it and, for bonus points, who can do so in the form of a car analogy?

Re:Gravitational quantum states of neutrons, eh? (2)

JonySuede (1908576) | more than 3 years ago | (#35861996)

You see, cars are attracted to other cars and there are some grooves on the road so a car usually stays jammed into one of them. While there it is both morphed a corresponding Transformer (the transfomer depending of the groove and the car) and the car but if you look at it you may see a car or you may see a transformer ex: Megateron. I hope that this clarify any doubts you had about gravitational quantum transformers.

Neutron's Law of Gravity.. (0)

angiasaa (758006) | more than 3 years ago | (#35861764)

Another chapter added to kindergarten physics

ummm (0)

Anonymous Coward | more than 3 years ago | (#35861770)

forgive me for this stupid question, but if neutrons have 0 charge, by what means does the upper plate attract them and the bottom plate repel them? Shouldn't the neutrons just ignore the presence of the plates and fall toward the center of the earth, aka down? or do we already have anti-gravity technology that i am not aware of

Re:ummm (2)

multi io (640409) | more than 3 years ago | (#35862034)

forgive me for this stupid question, but if neutrons have 0 charge, by what means does the upper plate attract them and the bottom plate repel them? Shouldn't the neutrons just ignore the presence of the plates and fall toward the center of the earth, aka down? or do we already have anti-gravity technology that i am not aware of

I didn't RTFA, but the "charge" for gravity is called "mass", which neutrons have, and the earth's gravity could be neutralized by setting up the plates vertically, so any movement of the neutrons towards the earth's center wouldn't coincide with a movement towards one of the plates. Oh, and both plates may attract the neutrons -- the summary only said that once the neutrons reached the plate surface, one of the plates would absorb the neutrons, and the other plate would reflect them.

Re:ummm (5, Informative)

blair1q (305137) | more than 3 years ago | (#35862086)

According to the links, one plate is smooth, and the other is rough. so a neutron will glide over the smooth plate or be scattered at small angles but if it hits the rough plate it will be scattered more, on average. Why the difference? So that they have a different effect and you can tell if perturbing their course causes more to hit the smooth plate or the rough one.

The neutron's course can be perturbed by gravity. In the steady state, this means the neutron just drops in a parabolic arc following gravity, which at these length scales (microns) can be more determined by massive nearby objects (1/r^2 is huge) than by the distant center of the Earth (1/r^2 is tiny). (You might even get a setup where the top plate gravity is equal and opposite to the Earth's gravity, for objects that are close enough.)

Moving one plate nearer or farther away makes the arc change shape, changing how many neutrons are scattered for a given beam intensity and launch angle. Moving the plate in an oscillating motion at a given magnitude should give you an oscillating scattering measurement with a fairly constant magnitude. You would expect the number of neutrons scattered to be irrelevant of the frequency, when averaged over many cycles of the oscillation, if you considered gravity to be purely Newtonian (i.e., Newtonian gravity, f = GmM/r^2, is monotonic with changes in r, even when r is changing with time).

But they don't see that. They see distinct frequencies of plate oscillation that result in bumps or sharp bends in the average scattering.

That says they're seeing non-monotonic, quantized, time-dependent effects that Einsteinian gravity suggests.

Re:ummm (0)

Anonymous Coward | more than 3 years ago | (#35864700)

this kinda makes sense since it explains a bit more than just saying "one plate repels and one attracts". By the the way, i still don't see how you can have gravity repel in any setup. and also, i dont see a direct connection between the conclusion and the experiment.. it could be something more along the lines of them seeing different harmonics of some resonance and not quantum levels of gravity.. thanks for responding anyways.. i feel like most slashdotters are not very big on physics haha

Re:ummm (0)

femtobyte (710429) | more than 3 years ago | (#35863262)

Neutrons can interact with other matter through more than electromagnetic forces. In the case of very slow moving neutrons like the ones used here, the typical interaction used to repel/attract neutrons from a material surface is the "Fermi potential," a quantum mechanical scattering potential between the free neutrons and the nuclei in the bulk of the material (which can be either attractive or repulsive depending on the material, typically in the range between +/-300neV). The neutrons don't fall through the plates for nearly the same reason that you don't fall through the seat below you (which, contrary to "popular knowledge," is not due to electrostatic forces between you and the chair, but rather due to electron degeneracy pressure).

Re:ummm (0)

Anonymous Coward | more than 3 years ago | (#35864650)

oh my god you just made a bunch of shit up

Now pay $18 (1)

frovingslosh (582462) | more than 3 years ago | (#35861772)

What a nice advertisement for an article that costs $18.

Re:Now pay $18 (3, Interesting)

pclminion (145572) | more than 3 years ago | (#35861918)

It's a citation. Nobody said it has to be easy to get. If you think the article submitter is actually a shill for Nature trying to drum up funds by getting a bunch of Slashdotters to pay $18 for a copy of the article, well, you're a new kind of crazy I haven't seen before.

Re:Now pay $18 (3)

MoonBuggy (611105) | more than 3 years ago | (#35862060)

Not to mention that the majority of people wanting to read the paper itself (rather than the abstract and BBC summary) are likely to have institutional access anyway.

Re:Now pay $18 (0)

Anonymous Coward | more than 3 years ago | (#35865492)

Quite a few universities are starting to think twice about access to nature and science... They charge a hell of a lot. And you still pay to get something published. Open access is where its at now days. Its only a matter of time before all government grants will require it.

Re:Now pay $18 (2)

Anne_Nonymous (313852) | more than 3 years ago | (#35862106)

>> well, you're a new kind of crazy I haven't seen before.

I'm offering an article on the taxonomy of crazy for only $18, if you're interested.

Re:Now pay $18 (1)

blair1q (305137) | more than 3 years ago | (#35862110)

Actually, the links point to enough information that having the article could only help you replicate their setup exactly.

But it'd be better if you just replicated the idea in another fashion, to remove systematic bias their setup may have had.

So save your $18; you're going to need it to pay postage for your grant application.

Re:Now pay $18 (0)

Anonymous Coward | more than 3 years ago | (#35862312)

For a one-year subscription you'd probably be able to buy a small car (new). I guess I feel a divine calling... [slashdot.org] (link $0.00).

Neutrons (0)

Anonymous Coward | more than 3 years ago | (#35861808)

Questions
1. How does the plate absorb neutrons.
2. How does the plate reflect neutrons.
3. Neutrons are neutral, how does the piezoelectric affect the motion?

WhatMeWorry

Re:Neutrons (2)

blair1q (305137) | more than 3 years ago | (#35862138)

1. The neutrons hit the nuclei of the atoms in the plate.

2. When the nuclei are lined up nicely the neutrons are absorbed or glance-off in a more regular fashion; when the nuclei are in lumpy bumps, they are absorbed or glance off in more random fashion.

3. The piezo is only used as a motor to move the plate. The fact that it's piezoelectric is irrelevant and should have been left out. It could have been a servo or a twisted rubber band.

Some of the Article Text (4, Informative)

catchblue22 (1004569) | more than 3 years ago | (#35862054)

Here are a few paragraphs of the original article:

Spectroscopy is a method typically used to assess an unknown quantity of energy by means of a frequency measurement. In many problems, resonance techniques1, 2 enable high-precision measurements, but the observables have generally been restricted to electromagnetic interactions. Here we report the application of resonance spectroscopy to gravity. In contrast to previous resonance methods, the quantum mechanical transition is driven by an oscillating field that does not directly couple an electromagnetic charge or moment to an electromagnetic field. Instead, we observe transitions between gravitational quantum states when the wave packet of an ultra-cold neutron couples to the modulation of a hard surface as the driving force. The experiments have the potential to test the equivalence principle3 and Newton’s gravity law at the micrometre scale

Generally, a quantum mechanical system that is described by two states can be understood in analogy to a spin-1/2 system, where the time development is described by the Bloch equations, assuming two states of a fictitious spin in the multiplet, similar to spin-up and spin-down states. In magnetic resonance of a standard spin-1/2 system, the energy splitting results in the precession of the related magnetic moment in the magnetic field. Transitions between the two states are driven by a transverse magnetic radio frequency field. Similar concepts can be applied to any driven two-level system, for example in optical transitions with light fields. Variations are inherently connected to high-precision measurements such as atomic clocks6, atom interferometry7, nuclear magnetic resonance8, quantum metrology9 and the related spin-echo technique10. The sensitivity reached so far11 in the search for the electric dipole moment of the neutron is 6.8×1022eV, or one Bohr rotation every six days.

In this Letter, we demonstrate that energy eigenstates in the gravity potential of the earth can be probed using a new resonance-spectroscopy technique, using neutrons bounced off a horizontal mirror. This spectroscopy technique has in common the property that a quantum-system is coupled to an external resonator. Quantum mechanical transitions with a characteristic energy exchange between the coupling and the energy-levels are observed on resonance. A novelty of this work is the fact that the quantum mechanical transition is driven by an oscillating field that does not directly couple an electromagnetic charge or moment to an electromagnetic field. Instead, we observe energy transfer on resonance that is based on gravity-quantum states coupled to a modulator. We have named this technique gravity resonance spectroscopy, because the energy difference between these states has a one-to-one correspondence to the frequency of the modulator, in analogy to the nuclear magnetic resonance technique, where the energy splitting of a magnetic moment in an outer magnetic field is related to the frequency of a radio-frequency field. This is possible because of the feature of the quantum bouncing ball12, 13 that the levels are not equidistant in energy. The linear gravity potential leads to measured14, 15, 16 discrete non-equidistant energy eigenstates |nright fence. A combination of any two states can therefore be treated as a two-level system, as each transition can be addressed by its unique energy splitting or, in our case, by vibrating the mirror mechanically at the appropriate frequency. It has also been proposed to realize transitions between gravitational quantum states by means of oscillating magnetic gradient fields17. The physics behind these transitions is related to earlier studies of energy transfer where matter waves bounce off a vibrating mirror18, 19 or a time-dependent crystal20, 21. In the latter case the transitions are between continuum states, in the quantum bouncer the transitions are between discrete eigenstates. Optical dipole traps of atoms are reviewed in ref. 22.

Re:Some of the Article Text (0)

Anonymous Coward | more than 3 years ago | (#35866844)

Cue your Righthaven lawsuit in 3..2...1...

Re:Some of the Article Text (1)

catchblue22 (1004569) | more than 3 years ago | (#35867728)

It is only a small part of the article. Without graphs, and without without references. To anyone seeking to use this for academic purposes it would be largely useless. Still...

insert technobabble here ... (1)

Spectre (1685) | more than 3 years ago | (#35862094)

Is it just me, or does that summary seem to be narrated by Geordi La Forge?

Stupid question of the day!!! (1, Offtopic)

Xaedalus (1192463) | more than 3 years ago | (#35862198)

Could gravity then be a function of resonance rather than mass?

Neutrons (1)

PoopJuggler (688445) | more than 3 years ago | (#35862264)

Question. TFA says that because neutrons have no charge they "are as isolated from all the forces of nature as they can possibly be, with only gravity to act on them." Then they say they have a metal plate that repels them, and one that attracts them. Seems contradictory... ?

Re:Neutrons (3, Insightful)

femtobyte (710429) | more than 3 years ago | (#35863052)

The way that the lower/upper plates "repel/attract" the neutrons is not to be due to familiar forces (e.g. electromagnetic, gravitational, weak, strong), but rather due to quantum scattering effects from the bulk of nuclei in the plate material (which can be either attractive or repulsive, depending on material composition) based on the Fermi exclusion principle (identical fermions, such as neutrons, cannot occupy the same quantum state, resulting in effective forces between them not caused by any other forces). While the statement (as is often true of science journalism for the general public) is unclear and confusing, it is somewhat true in the sense that the neutrons are not interacting through a mechanism that would show up on a list of "forces of nature".

It's just another example of senile useless re-sea (0)

Anonymous Coward | more than 3 years ago | (#35862290)

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.

http://www.fullmalls.com (-1, Offtopic)

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anti-gravity machine? (0)

Anonymous Coward | more than 3 years ago | (#35864288)

I'm not a physicist. My understanding of the experiment is this: a neutrino is shot between two plates. If it is shot with sufficient energy it emerges from the far end of the plates and hits an instrument which records the impact. If the neutrino is shot with less that sufficient energy, the gravitational pull on the particle alters the course of the particle such that it impacts the bottom plate, where it is reflected (bounces), and presumably then is absorbed by the top plate. If a particle is shot with an amount of energy that would not be sufficient to get the particle out the far side of the plates BUT then the experimenters vibrate the bottom plate at a specific frequency such that a precise quantum amount of energy is induced into the particle, it will pass through the plates ... is this not the basis of a mechanism that counteracts gravity? An anti-gravity machine as it were? Really?

Re:anti-gravity machine? (1)

Muad'Dave (255648) | more than 3 years ago | (#35867642)

Neutron != neutrino.

Technobabble or Magic? (1)

ukemike (956477) | more than 3 years ago | (#35864308)

Any sufficiently advanced science is indistinguishable from Star Trek technobabble.

a bit one-sided (2)

kubitus (927806) | more than 3 years ago | (#35865120)

at least on the Authorship:

1.

Atominstitut, Technische Universität Wien, Stadionallee 2, 1020 Vienna, Austria

* Tobias Jenke,

* Hartmut Lemmel &

* Hartmut Abele

2.

Institut Laue-Langevin, 6, Rue Jules Horowitz, 38042 Grenoble Cedex 9, France

* Peter Geltenbort &

* Hartmut Lemmel

3.

E18, Physikdepartment, Technische Universität München, 85748 Garching, Germany

* Hartmut Abele

4.

Physikalisches Institut, Universität Heidelberg, Philosophenweg 12, 69120 Heidelberg, Germany

* Hartmut Abele

Can it solve the "Kilogram standard" problem? (0)

ryzvonusef (1151717) | more than 3 years ago | (#35865182)

Now I will freely admit that my education in Physics is abysmal (I got a D in my Physics A-levels :( ), but utilising the god^H^H^Hslashdot-given-right to talk on any topic without even RTFA, I ask a question:

Can it solve the "Kilogram standard [slashdot.org] " problem we keep hearing about?

Or am I barking up the wrong tree?

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