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Quantum Gravity Observed
Lawrence_Bird writes "AIP News is reporting the first observations of quantum gravitational states by researchers in Grenoble using a beam of ultra cold neutrons. This is an incredible observational achievement when you consider the energies involved - order of 1 pico electron volt (10^ -12eV). The full paper is in the 17 Jan Nature."
http://simscience.org/membranes/advanced/essay/qua ntum_grav1.html
...has a pretty interesting explaination of quantum gravity and how it ties in with Einstien's Relativity and quantum mechanics, the two bedrocks of modern physics.
-- Your local friendly mad scientist-in-training
the fixed url.
Brief but nice overview of quantum gravity:
Quantum Gravity @ Dr. Jim Jessen
The experiment is basically the same one that discovered the electron (with a few details changed).
In essence, if you select a mass small enough, you may be able to observe its interaction with individual quanta. What these people did was to slow the neutron down so much that they could see it fall under gravity. Their idea was that in stead of falling in a parabola, you should be able to see the polygon sides as the individual quanta hit, or downwards speeds quantised at different multiples of a base. It is this second element that they observed.
Since in the past, this yielded the experimental evidence for the electron, here it yields what could be experimental data for the graviton.
OS/2 - because choice is a terrible thing to waste.
Absolutely none. String theory contains a theory of quantum gravity. But as pointed out correctly by the Anonymous Coward above, this discovery is not a discovery of "quantum gravity", as the term is usually used. They have discovered quantization of neutron orbits in the classical gravitational potential, analagous to the quantization of electron orbits around a proton. (You know, the s,p,d,f energy levels from chemistry?) At low energies (and these are VERY low energies), our classical picture of gravity is extremely accurate, and there's not a graviton in sight. Experimental proof that the graviton exists would be proof of quantum gravity.
Discovering quantum gravity is much, much harder. The energy scale at which quantum gravity becomes important is 10^19 GeV (note 1 GeV/c^2=mass of proton). The accelerators we're building now are 2000 GeV. We won't get to 10^19 in our lifetimes, if ever. There has been a flurry of papers recently saying that we might see quantum gravity at current or near-term accelerators, but they do this by invoking extra dimensions. In other words, curled up extra space-time dimensions that are as big as 100um, and only gravity propegates in the extra dimensions. This has the effect of lowering the energy scale at which gravity becomes important, so that we might be able to see it.
But if that 10^19 figure is really correct, we ain't gonna see quantum gravity anytime soon. Unfortunately...
--Bob
1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.
The Higgs Boson is part of the Standard Model, which is a Quantum Field Theory. (Note the "Quantum" in "Quantum Field Theory") It is not a classical theory. Perhaps you meant "Standard Model" rather than "Classical Theory". The word "Classical" to a physicist means "non-quantum".
As Schrodinger might say, there's more than one way to skin a cat, and there are is more than one way to give mass to the W and Z bosons (which is why we want the higgs). It has been proposed, for instance, that there are several higgs', separated in energy by about 10GeV. This could be responsible for the experimental evidince seen at LEP2 just before it was shut down. One thing is clear, however. Whether or not we find the higgs boson, the LHC (next accelerator at CERN) must find new phenomena. Some of our calculations simply don't make sense as you increase the energy. The higgs is a good, simple solution to part of the problem, but that doesn't mean it's necessarily correct. We theorists like to pretend we know what we'll see (SUSY/Extra Dimensions/Higgs) but I like to keep my mind open and hope that we'll be surprised by what we see at the LHC.
--Bob
1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.