エトヴェシュ・ロラーンド
A new fundamental force might be difficult to test. Gravity, for example, is such a weak force that the gravitational interaction between two objects is only significant when one of them has a great mass. Therefore, it takes very sensitive equipment to measure gravitational interactions between objects that are small compared to the Earth. A new (or "fifth") fundamental force might similarly be weak and therefore difficult to detect. Nonetheless, in the late 1980s a fifth force, operating on municipal scales (i.e. with a range of about 100 meters), was reported by researchers (Fischbach "et al.") who were reanalyzing results of Loránd Eötvös from earlier in the century. The force was believed to be linked with hypercharge. Over a number of years, other experiments have failed to duplicate this result.