The speed of gravitational waves (v g) is predicted by general relativity to be the speed of light (c). The extent of any deviation from this relationship can be parameterized in terms of the mass of the hypothetical graviton. The graviton is the name given to an elementary particle that would act as the force carrier for gravity, in quantum theories about gravity. It is expected to be massless if, as it appears, gravitation has an infinite range. (This is because the more massive a gauge boson is, the shorter is the range of the associated force; as with the infinite range of electromagnetism, which is due to the massless photon, the infinite range of gravity implies that any associated force-carrying particle would also be massless.) If the graviton were not massless, gravitational waves would propagate below lightspeed, with lower frequencies (ƒ) being slower than higher frequencies, leading to dispersion of the waves from the merger event. No such dispersion was observed. The observations of the inspiral slightly improve (lower) the upper limit on the mass of the graviton from Solar System observations to 2.1 × 10 kg, corresponding to 1.2 × 10 eV / c or a Compton wavelength (λ g) of greater than 10 km, roughly 1 light-year. Using the lowest observed frequency of 35 Hz, this translates to a lower limit on v g such that the upper limit on 1- v g / c is ~ 4 × 10.