Using Neutrons To Precisely Test Newton's Law of Gravity 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."
Re:Newton's (Score:5, Interesting)
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:Now pay $18 (Score:4, Interesting)
Re:this is wrong (Score:1, Interesting)
the bible doesn't talk about neutrons
You're holding it wrong.
Re:Newton's (Score:4, Interesting)
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 (Score:4, Interesting)
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 (Score:4, Interesting)
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 (Score:2, Interesting)
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)