Is 2 fifths more or less than 1 half?

Think that Einstein's theory of gravity will have to be modified, not at small scales, but at large distances, or, equivalently, small accelerations. They point out that dark matter, dark energy and even the Pioneer anomaly are unexplained by the Standard Model of particle physics and suggest that some modification of gravity, possibly arising from Modified Newtonian Dynamics or the holographic principle. This is fundamentally different from conventional ideas of a fifth force, as it grows stronger relative to gravity at longer distances.

, however, think that dark matter and dark energy are not ad hoc, but are supported by a large number of complementary observations and described by a very simple model. On April 6, 2011 there was a possible discovery at Fermilab’s Tevatron that, according to physicists, could transform all of high energy physics. The possibility of discovering the elusive 'fifth force' is based on 4.3 inverse femtobarns of data.

The CDF collaboration will repeat the analysis with at least twice as much data to see whether the bump gets more or less pronounced. Other experiments, including DZero and the LHC experiments, will look for a particle of about 140 GeV/c2 in their data as well. ^ Ephraim Fischbach, Daniel Sudarsky, Aaron Szafer, Carrick Talmadge, and S.

Aronson, "Reanalysis of the Eötvös experiment", Physical Review Letters 56 3 (1986). ^ University of Washington Eöt-Wash group, the leading group searching for a fifth force. ^ Satellite Energy Exchange (SEE) 1, which is set to test for a fifth force in space, where it is possible to achieve greater sensitivity.

Zumberge, et al. "Test of Newton's inverse-square law in the Greenland ice cap.".