Editing Fifth force (section)

===Extra dimensions===
Another kind of fifth force, which arises in [[Kaluza–Klein theory]], where the universe has [[extra dimensions]], or in [[supergravity]] or [[string theory]] is the [[Yukawa potential|Yukawa force]], which is transmitted by a light scalar field (i.e. a scalar field with a long [[Compton wavelength]], which determines the range). This has prompted a much recent interest, as a theory of [[supersymmetric]] large extra {{nowrap|dimensions{{tsp}}{{mdash}}}}{{tsp}}dimensions with size slightly less than a {{nowrap|millimeter{{hsp}}{{mdash}}}}{{tsp}}has prompted an experimental effort to test gravity on very small scales. This requires extremely sensitive experiments which search for a deviation from the [[inverse-square law]] of gravity over a range of distances.<ref>{{cite web |url=http://www.phys.utk.edu/see/ |title=Satellite Energy Exchange (SEE) |access-date=2005-05-07 |url-status=dead |archive-url=https://web.archive.org/web/20050507195406/http://www.phys.utk.edu/see/ |archive-date=2005-05-07 |df=dmy-all}}, which is set to test for a fifth force in space, where it is possible to achieve greater sensitivity.</ref> Essentially, they are looking for signs that the Yukawa interaction is engaging at a certain length.

Australian researchers, attempting to measure the [[gravitational constant]] deep in a mine shaft, found a discrepancy between the predicted and measured value, with the measured value being two percent too small. They concluded that the results may be explained by a repulsive fifth force with a range from a few centimetres to a kilometre. Similar experiments have been carried out on board a submarine, [[USS Dolphin (AGSS-555)|USS ''Dolphin'' (AGSS-555)]], while deeply submerged. A further experiment measuring the gravitational constant in a deep borehole in the Greenland ice sheet found discrepancies of a few percent, but it was not possible to eliminate a geological source for the observed signal.<ref>{{cite journal |last1=Ander |first1=Mark E. |last2=Zumberge |first2=Mark A. |last3=Lautzenhiser |first3=Ted |last4=Parker |first4=Robert L. |last5=Aiken |first5=Carlos L. V. |last6=Gorman |first6=Michael R. |last7=Nieto |first7=Michael Martin |last8=Cooper |first8=A. Paul R. |last9=Ferguson |first9=John F. |last10=Fisher |first10=Elizabeth |last11=McMechan |first11=George A. |last12=Sasagawa |first12=Glenn |last13=Stevenson |first13=J. Mark |last14=Backus |first14=George |last15=Chave |first15=Alan D. |last16=Greer |first16=James |last17=Hammer |first17=Phil |last18=Hansen |first18=B. Lyle |last19=Hildebrand |first19=John A. |last20=Kelty |first20=John R. |last21=Sidles |first21=Cyndi |last22=Wirtz |first22=Jim |title=Test of Newton's inverse-square law in the Greenland ice cap |journal=Physical Review Letters |date=27 February 1989 |volume=62 |issue=9 |pages=985–988 |doi=10.1103/PhysRevLett.62.985 |pmid=10040395 |bibcode=1989PhRvL..62..985A }}</ref><ref>{{cite journal |last1=Zumberge |first1=Mark A. |last2=Ander |first2=Mark E. |last3=Lautzenhiser |first3=Ted V. |last4=Parker |first4=Robert L. |last5=Aiken |first5=Carlos L. V. |last6=Gorman |first6=Michael R. |last7=Nieto |first7=Michael Martin |last8=Cooper |first8=A. Paul R. |last9=Ferguson |first9=John F. |last10=Fisher |first10=Elizabeth |last11=Greer |first11=James |last12=Hammer |first12=Phil |last13=Hansen |first13=B. Lyle |last14=McMechan |first14=George A. |last15=Sasagawa |first15=Glenn S. |last16=Sidles |first16=Cyndi |last17=Stevenson |first17=J. Mark |last18=Wirtz |first18=Jim |title=The Greenland Gravitational Constant Experiment |journal=Journal of Geophysical Research |date=1990 |volume=95 |issue=B10 |pages=15483 |doi=10.1029/JB095iB10p15483 |bibcode=1990JGR....9515483Z |url=https://zenodo.org/record/1231434 }}</ref>