In physics, Kaluza–Klein theory (KK theory) is a unified field theory of gravitation and electromagnetism built around the idea of a fifth dimension beyond the usual four of space and time. It is considered to be an important precursor to string theory.
Sidereal day（恒星日）：A sidereal day is the length of time it takes a planet to rotate from the perspective of a distant star. For the planet Earth a sidereal day is approximately 23 hours, 56 minutes, and 4 seconds.Astronomers use sidereal time to keep track of the direction to turn the telescopes to view a star in the night sky. By contrast, solar time is reckoned by the movement of the Earth from the perspective of the Sun. An average solar day (24 hours) is longer than a sidereal day (23…
The Cassini Division is a 4,800 km (3,000 mi) wide region between the A Ring and B Ring. It was discovered in 1675 by Giovanni Cassini at the Paris Observatory using a refracting telescope that had a 2.5 inch objective lens with a 20 foot long focal length and a 90x magnification. From Earth it appears as a thin black gap in the rings. However, Voyager discovered that the gap is itself populated by ring material bearing much similarity to the C Ring.
The Kuiper belt /ˈkaɪpər/ or 'køypǝr (as in Dutch), sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but it is far larger—20 times as wide and 20 to 200 times as massive. Like the asteroid belt, it consists mainly of small bodies, or remnants from the Solar System's formation.