"One of the great missions for the 21st century could be FOCAL — a space probe sent to the Sun’s gravity lens some 550 AU out." For comparison, the "straight l

"One of the great missions for the 21st century could be FOCAL — a space probe sent to the Sun’s gravity lens some 550 AU out." For comparison, the "straight line" distance from Earth to Pluto recently traversed by New Horizons is about 31.9 AU. Thats about 3 billion miles, and took nearly ten years. 550 AU is a long walk.