Law & Disorder
Physicists keep trying to explain why time flows one way
In a famous passage from his 1938 book The Realm of Truth, the Spanish-American philosopher George Santayana compared time to a flame running along a fuse. The flame’s position marked the present moment, speeding forward but never backward as the fuse disappeared behind it. “The essence of nowness,” Santayana remarked, “runs like fire along the fuse of time.” Each spark along the fuse represents one of the “nows” that transform the future into the past and “combine perfectly to form the unchangeable truth of history.”
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It’s far from a perfect analogy. A flame flitting along a wire doesn’t fully capture the quirky features of time that perplex physicists pondering relativity and quantum mechanics, for example. But Santayana’s sparks do illustrate one of time’s most enduring and puzzling properties — its irreversibility.