Equivalence of Active and Passive Gravitational Mass Tested with Lunar Laser Ranging

Lunar Laser Ranging (LLR) measures the distance between observatories on Earth and retro-reflectors on the Moon since 1969. In this Letter, we study the possible violation of the equivalence of passive and active gravitational mass ($m_a/m_p$), for aluminum (Al) and iron (Fe), using LLR data. Our new limit of $3.9\times {10}^{-14}$ is about 100 times better than that of Bartlett and Van Buren [Equivalence of Active and Passive Gravitational Mass Using the Moon, Phys. Rev. Lett. 57, 21 (1986)] reflecting the benefit of the many years of LLR data.

Figure 1

Geocentric change of position of the tide generating body due to time delay [16].