Physicists Clarify Exotic Force 86
Azazel writes "A research group, including Purdue University physicist Ephraim Fischbach, has completed an experiment which shows that gravity behaves exactly as Isaac Newton predicted, even at small scales. Unfortunately for those in search of the so-called "Theory of Everything," the finding would seem to rule out the exceptions to his time-honored theories that physicists believe might occur when objects are tiny enough."
Re:Did I miss something? (Score:4, Insightful)
Yes and no...what's noteworthy about this experiment is what they didn't find. Much like the Michelson-Morley experiment [wikipedia.org] in 1887, which set out measure the 'aether', and instead failed utterly to detect any such thing, this experiment was devised to detect exceptions to the behavior of gravity on a quantum scale, and found no such exceptions.
Ephraim's not giving up yet, though...he plans on developing another experimental apparatus that is a million times more sensitive than the one that was used in this experiment. Also, even though this experiment was nominally a 'failure', the fringe benefit of clarifying the Casmir force is a big success.
Yes. . .everythings normal BUT. . . (Score:3, Insightful)
But what's eating all the theorists is that they have absolutely no idea why. The venerable laws of gravitation are empirical, in the sense that noone knows where it comes from other than the fact that it is associated with mass. All the other forces of nature have a quantum explanation, and have a particle that transmits them (most notably electromagnetism and photons). Noone has been able to satisfactorily reconcile gravity with any fundamental (quantum mechanical) nature of a particle.
It's almost scary that we know more about what binds subatomic particles together than what keeps the moon orbiting the earth. It's also ironic that most people's only introduction to physics is newtonian physics which is presented in textbooks as complete and understood. It's true we have the math to predict the effect of gravity to arbitrary precision, but I'm sure engineers can back me up that just because something has a robust empirical law doesn't mean anyone really understands how it works.
$\alpha \leq 10^{12}$? Why so large? (Score:3, Insightful)
So, as I see it, they've shown that this "other" interaction is less than a million million times stronger than Newtonian gravity, right? Until $\alpha \approx 1$, I wouldn't say they've "shown that gravity behaves exactly as Isaac Newton predicted". This is interesting, of course, but there's a long way to go. Fortunately they conclude their Letter by saying they expect to be able to get limits on $\alpha$ down to 10^6 with $\lambda\approx 100nm$. We'll be looking forward to it.
As a side note, it'd be really nice if /. learned to render TeX for any non-physicists who might be reading this.
Re:What? (Score:2, Insightful)
That's more or less what relativity says. It's not so much that your velocity always adds up to the speed of light, however, as it is that we are travelling on a four dimensional vector. i.e. Just as a car traveling in a diagonal path has a slower southward velocity than a car travelling at the same speed but heading due south, so is our apparent velocity through time affected as we "turn" more into the three dimensions that we know.
I must admit, that idea made me stop and re-read that section of the book a couple of times, as I'd never heard relativity expressed that way before.
One important thing to remember is that there are two theories: The General Theory of Relativity (i.e. Gravity) and The Special Theory of Relativity (i.e. Space-Time Warps). Most people are referring to the former when they speak of relativity, thus causing no end of confusion.