The most careful and respected experimental group in its field which resides at University of Washington - Eric Adelberger et al. - seems to have detected deviations from Newton's gravitational law at distances slightly below 100 microns at the "4 sigma" confidence level. Because they are so careful and the implied assertion would be revolutionary (or, alternatively, looking spectacularly dumb), they intend to increase the effect to "8 sigma" or so and construct different and complementary experiments to test the same effect which could take a year or two (or more...) before the paper is published. You know, there are many things such as the van der Waals forces and other, possibly unexpected, condensed-matter related effects that become important at the multi-micron scales and should be separated from the rest.
Their measured force at these multimicron distances is weaker than expected from Newton's formula. This is unusual because in most models, one expects the force to grow stronger at short distances. For example, in theories with two
For the latest paper of that group - which could not announce any new effects yet - see
- Tom Banks' prolegomena 1988
- Silas Beane's sub-centimeter paper 1997
- Raman Sundrum 1997
- Anthony Zee's fat graviton 2003
My thanks also go to Ann Nelson for her speedy and detailed comments about the history of these ideas.