When historians or scientists look back over huge cataclysmic events, they generally find some harbinger that went unnoticed at the time.
There’s always a warning. If you’re a chaos theorist, it’s the flapping of the proverbial butterfly’s wings in New York that caused a tsunami in Hong Kong. A meteorologist might think of it in terms of a category five hurricane that began as a low-pressure area off the Cape Verde Islands on the African coast. Historians remember the assassination of the Archduke Ferdinand as the spark for World War I.
When future historians begin to...