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The world shuddered under the shadow of the massive alien spacecraft, it having become visible to Earth's telescopes only days ago. The bowl-shaped vessel, several-hundred kilometers across, parked silently in orbit some three tenths of the way to the Moon, dark but for a band of blue encircling its rim, its intentions unknown and unknowable to man.

A week after its arrival, the message came, transmitted worldwide in multiple languages:
Inhaaaabitants of this woooorld. .... Youuuur system .... sitssss in the terrrrritory .... of the Sleureuk't'hakk Empiiiire. .... You musssst .... choooooose. .... Submiiiit willllinglllly.... to Sleureuk't'hak ruuuule .... orrrr .... beeeeeee enslaaaaved by fooooorce." Then, several minutes of silence; and then a brief follow-up message: "This vessssellll.... willll reeeeturn to youuuurrrr system .... in twenty-fiiiive nanoklopts, to receeeeive youuuurrrr answerrrr.
A flurry of debate exploded amongst the leaders of Earth -- how to respond? Acceptance? Defiance? An attempt at negotiation? Time was surely running out; they had been given twenty-five nanoklopts, whatever that meant, and it sure didn't sound like a lot. Which led to debate on how soon an answer could possibly reasonably be expected, which led to the only point of agreement reached amongst the leaders, that being that the meaning of nanoklopt had to be figured out. A message was directed back toward the alien spacecraft: "Just how much time is a nanoklopt?"

The ship sat silently for five days before, with a certain suddenness, the answer came:
One nanoklopt .... is.... apprrrroximately the tiiiime.... of threeeeee orrrrbits.... of the eighth plaaaanet.... of youuuur system."
The NASA eggheads listening to the response didn't even need to look in a book; the eighth planet, Neptune. Orbital period: 164.79 years. Times three -- 494.37 years; times twenty-five -- 12,359.25 years. After more discussion, this time considerably less hurried, the leaders of Earth came to an agreement on a response to be conveyed towards the waiting spacecraft: "We'll let you know."

The spacecraft sat silently for another five days, and then, as abruptly as its arrival, it began to move away from the Earth, on the long journey to its next destination.