The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It […]
Uranus (from the Latin name Ūranus for the Greek god Οὐρανός) is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary […]
The Voyager program is an American scientific program that employs two roboticprobes, Voyager 1 and Voyager 2, to study the outer Solar System. The probes were launched in […]
The Gregorian calendar is the most widely used civil calendar in the world.[Note 1] It is named after Pope Gregory XIII, who introduced it in October 1582. The calendar spaces leap years to make the average year 365.2425 days long, approximating the 365.2422 day tropical year that is determined by the Earth’s revolution around the Sun.