How many sides does a typical snowflake have?

Which optical instrument has a type named for Johannes Kepler? Which name belongs to both a class of U.S. attack submarines and a 1904 Jack London novel? Which word names both a vacation on a ship and a type of missile? What is a wide, triangular necktie knot called? Which number of degrees means a U-turn or a complete reversal of opinion? Which unit used in commerce equals 42 gallons of crude oil? Which unit of distance equals 220 yards, or one-eighth of a mile? Which unit of energy does the abbreviation kWh stand for?