Chronometer, a timepiece that is exceptionally accurate. Traditionally, the term refers to the marine chronometer, a rugged mechanical instrument used at sea to keep time for navigational purposes. By measuring the position of a celestial body (with a device called a sextant), and by knowing the exact time of the measurement, a navigator can determine a ship's longitude from published tables. The typical marine chronometer is mounted on suspension devices called gimbals to keep it in a horizontal position and to reduce the effect of vibrations from the ship.
Nebulae are collections of dust and gases scattered across the galaxy. They're the sites where stars are born and what's left behind after they die.
Albert Einstein was a pretty smart guy. When you look up the word "genius" in the dictionary, so the saying goes, it's a pretty safe bet you'll see Einstein's mug. Think you’re smart enough to take on a quiz about the famed thinker?