query: What is the largest unit of time?
passage: Unit of time
The jiffy is the amount of time light takes to travel one fermi (about the size of a nucleon) in a vacuum. Planck time is the time light takes to travel one Planck length. Theoretically, this is the smallest time measurement that will ever be possible. Smaller time units have no use in physics as we understand it today. The TU (for Time Unit) is a unit of time defined as 1024µs for use in engineering. The Svedberg is a time unit used for sedimentation rates (usually of proteins). It is defined as 10−13 seconds (100 fs). The galactic year, based on the rotation of the galaxy, and usually measured in million years.[2] The geological time scale relates stratigraphy to time. The deep time of Earth’s past is divided into units according to events which took place in each period. For example, the boundary between the Cretaceous period and the Paleogene period is defined by the Cretaceous–Paleogene extinction event. The largest unit is the supereon, composed of eons. Eons are divided into eras, which are in turn divided into periods, epochs and ages. It is not a true mathematical unit, as all ages, epochs, periods, eras or eons don't have the same length; instead, their length is determined by the geological and historical events that define them individually.
passage: Earth Hour
About 4000 cities participated, including landmarks such as Big Ben, the Empire State Building, the Sydney Opera House, the Eiffel Tower, the Parthenon, the Brandenburg Gate, and the Forbidden City.Earth Hour 2011 was the biggest year in the campaign's five-year history, reaffirming it as the largest ever voluntary action for the environment. In 2011, the tagline "Beyond the Hour" was adopted by organizers as a way to encourage people to take their commitment to the cause beyond the 60-minute event. Together with agency Leo Burnett, Earth Hour unveiled an updated planet themed logo that included a small plus symbol to the right of the signature "60" which was used in previous years. The 60+ symbol continues to be the main logo used by campaign organizers around the world.