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.
We take much for granted about our universe, like it's getting bigger. What if the universe stopped expanding and started collapsing inward with a giant crunch?
There's a 45-million-ton asteroid out there with Earth's name on it. In 2029, it'll be closer to us than our moon is. And that's not even the fly-by that scientists are worried about.