In 2016 the LIGO-Virgo collaboration announced “the first direct detection of gravitational waves.” This was to distinguish their result from the indirect observation of Russell Hulse, Joel Weisberg, and Joseph Taylor, which used the decrease in the period of a binary pulsar to “establish, with a high degree of confidence the existence of gravitational radiation as predicted by general relativity.” This raises several interesting questions. One might ask how one can distinguish between direct and indirect observation and whether that distinction is exemplified in the practice of science. One might also ask whether a direct observation has more epistemic weight than an indirect observation. In this essay, I briefly discuss several episodes from the history of modern physics in an attempt to answer those questions. These episodes include Galileo and falling bodies, the discovery of the neutrino, the Higgs boson, and gravitational radiation.
