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Physicists at the Lawrence Berkeley National Laboratory and the University of California have successfully measured a force of 42 yoctonewtons -- the smallest ever.

To get an idea of how small that is, one newton is roughly the force exerted on your hand by an apple due to gravity. A yoctonewton is 0.000000000000000000000001 times that amount - unimaginably tiny, in other words.

More interestingly, it's only a factor of four above the standard quantum limit- a number that represents the most sensitive measurement that it's possible to make by our current understanding of physics.

The team did it with a combination of lasers and an optical trapping system comprised of a cloud of very cold atoms. Or as Dan Stamper-Kurn, one of the physicists involved explains: "We applied an external force to the center-of-mass motion of an ultracold atom cloud in a high-finesse optical cavity and measured the resulting motion optically. When the driving force was resonant with the cloud's oscillation frequency, we achieved a sensitivity that is consistent with theoretical predictions." Yup.

That super-accurate setup should allow physicists to test whether Newtonian gravity applies in the quantum world, and could also help us improve our most accurate microscopes.

In the meantime, colder atoms and better optical detection should allow the researchers to get even closer to the standard quantum limit. But before you get too impressed by that, you should know that we're behind schedule. "A scientific paper in 1980 predicted that the SQL might be reached within five years," said Sydney Schreppler, lead author of the paper describing the results in Science.

"It took about 30 years longer than predicted, but we now have an experimental set-up capable of reaching very close to the SQL."


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