So, today’s Daily Beast article celebrates testing one of the foundational concepts in Einstein’s general theory of relativity (and other gravitational theories): the equivalence principle. In its simplest form, it asserts that equal masses fall at the same rate, no matter what they are made of. At its most complex, it’s a statement about the fundamental nature of mass and its role in gravitation. Yet, because of the weakness of gravity, the equivalence principle is hard to test.
[O]nly a few specialized labs around the world are sensitive enough to measure gravity precisely. Some researchers even think we may be nearing the limits of what we can do on Earth’s surface, where any number of things can interfere. Small earthquakes, settling buildings, even tiny shifts in Earth’s gravitational field can add small amounts of uncertainty. The solution, of course, is to go into space, but naturally that has its own challenges. Not least of those worries: Even small space-based experiments are much more expensive than Earth-bound counterparts. [read more…]