Might a recent extrasolar visitor be an alien spacecraft?

'OUMUAMUA, an object tumbling through space that was discovered on October 19th, has already made history. The speed at which it is moving relative to the sun means that it cannot be native to the solar system. Its official designation is thus 1I/2017 U1, with the "I" standing for "interstellar"--the first time this designation has ever been used. That is exciting. Some scientists, though, entertain an even more exciting possibility: what if 'Oumuamua is not an asteroid, as most think, but an al...