Assertion: electron's mass | /r/HasProperty | discovered in mid-1970
Facets:
Source sentences:
text: However, the mass of the tau (discovered in the mid-1970s) (1777 MeV/c2) is nearly twice that of the proton and about 3,500 times that of the electron.
text: However, the mass of the tau (discovered in the mid 1970s) (7003177700000000000♠1777 MeV/c2) is nearly twice that of the proton, and about 3,500 times that of the electron.