GENEVA — It helps solve one of the most fundamental riddles of the universe: how the Big Bang created something out of nothing 13.7 billion years ago.

In what could go down as one of the great Eureka moments in physics — and win someone the Nobel Prize — scientists said Thursday that after a half-century quest, they are confident they have found a Higgs boson, the elusive subatomic speck sometimes called the ‘‘God particle.’’