As it has no mass, which particle travels at about 186,000 miles per second?

As in 2004, which event at the 1896 Athens Olympics finished at the Panathenaic Stadium, won by national hero Spyridon… Which Maryland city on the Chesapeake Bay is known in Navy slang as "Crabtown"? What does "anno Domini," as in A.D. 2000, mean in English? As it crosses Oklahoma, U.S. Highway 81 follows or parallels which famous 1800s cattle trail? Complete the saying: "Truth is stranger than ___." Which Pennsylvania governor from 1995 to 2001 became the first U.S. secretary of homeland security? As its cow-spotted packaging reflected, which computer company began marketing its products from an Iowa cattle farm in… As its title suggests, which Shakespeare comedy may have opened on January 6, 1601, a dozen evenings after Christmas?