Physicists Clarify Exotic Force

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."

Comments

Gravity at small length scales

[dr. loser]

IAAP (I am a physicist), and here's the deal:

There are suggestions out there that one way to test for the existence of extra "compactified" spatial dimensions (the kind of stuff needed in string theories) is to look for deviations from Newton's 1/r^2 gravity at small distance scales. See, for example, here.

The problem is, it's very hard to measure just the gravitational interaction between two objects separated at micron scales. Gravity is incredibly weak compared to common forces like electrostatics and magnetic interactions, and even more exotic things like Casimir forces (related to the van der Waals interaction).

The Purdue team has shown that the measured Casimir force in their experiment acts just as expected, setting a new limit on how screwy gravity can be at these distance scales.

For what it's worth, there are two other big efforts in this area. The one at Stanford is led by Aharon Kapitulnik, and is so sensitive that their apparatus can detect the different forces on Au and Si in the earth's magnetic field due to diamagnetism (!). The one at Washington is reportedly even more sensitive, and there are rumors circulating that they may have seen something exciting.

The really cool thing here is how table-top solid state experiments may have something profound to say about high energy physics, without any big accelerators.