Graviton discovered?

John Devers

Registered Senior Member
Does this mean the effects of the graviton have been discovered?

Or is it segments of space?

It sure sounds strange, as things fall they jump from one height to another.

<A HREF="" target=new><FONT COLOR=blue size=+1> Gravity leaps into quantum world

Researchers finally measure the subtle quantum effects of fourth fundamental force.
17 January 2002

Particles don't fall smoothly under gravity, they lurch.

Far from falling smoothly, objects moving under gravity do so in lurching, quantum leaps, a French experiment has revealed. The finding confirms that gravity, like the Universe's three other fundamental forces, can have a quantum effect.

Particles, such as electrons confined to their orbital shells around the nucleus of an atom, are restricted by the rules of quantum mechanics. To move from one position to another, they must jump to the next quantum state.

Theoretically, this rule holds for all matter under the influence of nature's four fundamental forces: electromagnetism, weak and strong nuclear force and gravity. But gravity, especially at small scales, is a very feeble force, making it extremely difficult to measure its quantum effects.

There's no point in looking for quantum behaviour in everyday objects. It is occurring, but the larger things become, the more subtle are the quantum effects. Even small molecules are practically immune to the weird ways of the quantum world.

Valery Nesvizhevsky and his colleagues studied ultracold neutrons (UCNs) at the Laue-Langevin Institute in Grenoble, France. These very slow-moving, uncharged particles normally team up with protons to form the nucleus of an atom. The team isolated the neutrons from the effects of the other three forces in a specially designed detector.

By following the progress of hundreds of UCNs falling from the top of the detector to the bottom, the team found that the particles exist only at certain heights. "They do not move continuously, but rather jump from one height to another as quantum theory predicts," says Nesvizhevsky.

That someone has measured quantum leaps has physicists wide-eyed. "The effects are so small it is remarkable that they can actually observe them," says Thomas Bowles, a particle physicist at Los Alamos National Laboratory in New Mexico.

Trick questions

This satisfying trick may also have profound implications for the future of physics. "Right now, we don't have a theory of how gravity is created," says Bowles. If refined, he says, apparatus like Nesvizhevsky's could explain how gravity behaves in the quantum world - and perhaps where it comes from.

We don't have a theory of how gravity is created
Thomas Bowles, Los Alamos National Laboratory

"If you're searching for something in fundamental physics, this is a very clean system," agrees Nesvizhevsky. It should allow researchers to pick apart some of the niggling questions about the fundamental properties of matter.

It might even be possible, suggests Bowles, to work out why Einstein's theory of general relativity - which explains gravity and large things, such as galaxies and the Universe - doesn't tally with quantum mechanics, the physicist's handbook of the very small.
seems to confirm for me that gravity is a pseudo-force and that general relativity is useful for large scale purposes though the reasoning is completely wrong
newton reasoned wrong but it's accuracy 4 many things in the macro world still STANDS TODAY
That's the coolest news in physics I've heard in a long time ... if true. I guess only time will tell - if others can repeat this experiment, then we can be confident of the results. More insight into solving the current problems with the Standard Model! And perhaps down the road, a union of general relativity with quantum physics, since gravity has ever been at the root of the problem.
when we use newton equation to solvemechanical problem, actually we just use simple form of einstein's relativity. just the velocity in newton equation is too small to be compared with speed of light, isn't it?

velocity of material in newton equation is ignored or have zero (0) value.
so, if speed of material can be ignored, we might be ignored the mass of neutron.

so, from the equation of gravitation force (F)=kMm/r^2,
where M is mass of earth, and m is mass of neutron which is ignored, therefore we will have equation like this:
F = k M 0/r^2
F = unlimited force.....this which might cause a quantum leap...
but i am still sceptic......somebody can show my my fault?
Hi SISGroup,

Not quite. Newtonian mechanics will never predict quantum leaps, since in its very basics the assumption that motion, space and time are continious, is used. The Newtonian description of a neutron falling would be (using the approximated F = m*g for gravitational interaction)

F = m*a = - m*g
<=> a = -g
<=> d<sup>2</sup>x/dt<sup>2</sup> = -g
<=> dx/dt = -g*t + constant = g*t + v<sub>0</sub>
<=> x(t) = -(1/2)*g*t<sup>2</sup> + v<sub>0</sub>*t + x<sub>0</sub>

Where x(t) denotes the position in the vertical direction at time t. As you can see, the position decreases continously as time evolves (given that v<sub>0</sub> = 0).

But as you probably know, Newtonian mechanics doesn't quite work out in the world of (elementary) particles: we use quantum mechanics to describe that world. One of the predictions of quantum mechanics is that energy is not a continous quantity, but changes only in small leaps. An electron bound to a nucleus cannot just have any energy. It is only allowed to have a set of very specific energylevels, and to go from one energylevel to another, the energy has to be brought in (or is emitted) in small energy packets, called photons. Coïncidently, energy can be associated with an average distance to the nucleus in an atom, so to get an electron closer to the nucleus, it has to make small energyjumps (which then correspond to small jumps in distance) to get closer.

I suspect (read: I am not sure how they did it, but what follows is what I guess they did)... So I suspect that the researchers measured the very same thing with the neutron: for it to get closer to earth, it makes small jumps in energy (corresponding to small jumps closer to earth). Because energy is easier to measure than distance in particle-situations, leaps of energy can be associated with leaps of distance (my guess is that every energyleap of the neutron corresponds to about a few picometres of distance). This would mean that the gravitational energy of the neutron also changes with small packets, called gravitons in this case.


if we can find energy which used by particle to make a quantumleap, therefore we will able to predict the movement of particle?
No, but if we see that the energyleaps really exist (and that the neutron does change energy continously) then this is a strong indication that gravitational energy is also exchanged into packets/gravitons. It is then up to a theory that is compatible with these gravitions to predict the correct movement of the neutron.


LIGO observatory to attempt to detect gravity waves

In this month's (April 2002) Scientific American:

Ripples in Spacetime

LIGO, a controversial observatory for detecting gravity waves, is coming online after eight years and $365 million.

This article isn't on Sciam's Internet site but if you're standing around a magazine rack this month, give it a read, it's quite amazing what they're trying to do. Give them a few decades and they might actually detect what they're looking for.

Thanks for those responses, it's hard to know exactly what the experiment is indicative of.

In one way of reading the article you get the impression that matter jumps through spacetime and flashes in and out of existance as it moves Another interpretation gives you that neutons have energy levels like electrons and jump from one to the next ass they fall in the experiment.

Only time will tell, here's the links to the experiment Weitzel mentions above.

<A HREF="" target=new><FONT COLOR=ff0098 size=+1> Laser Interferometer Gravitational Wave Observatory</FONT></A>

<A HREF="" target=new><FONT COLOR=ff0098 size=+1> LIGO Scientific Collaboration </FONT></A>