New Scientist and minimal length

New Scientist, a UK science magazine, covered our work on minimal length and quantum gravity. (Done while I was on sabbatical at Caltech.) You can compare the following summary to what I posted on this blog last November.

The smallest measurable length announced

27 November 2004. From New Scientist Print Edition.

PHYSICISTS have set a limit on the smallest length that can ever be measured - and any device that tries to beat the limit will be crushed into a black hole of its own making.

The finding is based on an analysis of interferometry, a technique that uses interference of waves to measure small lengths. Quantum theory says that the more accurate the measurement you want, the more massive the interferometer you need.

But Xavier Calmet, Michael Graesser and Stephen Hsu of the California Institute of Technology in Pasadena point out that any very massive interferometer would have to be spread over an extremely large region of space. Otherwise, the large mass concentrated in a small area would produce strong enough gravity to form a black hole, sucking in the interferometer.

But as the mass and the size are made ever larger to measure ever smaller lengths, the interferometer eventually becomes so big that its various components would not be able to interact fast enough for it to work, even using signals travelling at the speed of light.

Mathematically, these constraints lead to an instrument that can accurately measure only down to about 10-33 centimetres, a distance known as the Planck length (Physical Review Letters, vol 93, p 211101).