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GEOMETERS are wont to speak (it seems to me) somewhat laxly of “the line at infinity” as if there were only one such line in a plane; in a certain but not in the most obvious sense this is true—viz.

The universe is extremely vast, and even with modern science and technology, only a small amount is known about it. Humanity does not even have an answer to the age-old question, 'Is the universe ...