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Actual sunset: Two minutes before the Sun disappears below the horizon. Sunset (or sundown) is the disappearance of the Sun at the end of the Sun path, below the horizon of the Earth (or any other astronomical object in the Solar System) due to its rotation.
This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outside the atmosphere of Earth. The field of astronomy features an extensive vocabulary and a ...
An astronomical instrument is a device for observing, measuring, or recording astronomical data. [ citation needed ] They are used in the scientific field of astronomy , a natural science that studies celestial objects and the phenomena that occur in the cosmos, with the object of explaining their origin and evolution over time.
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. [1] [2] As one of the founders of the discipline, James Keeler, said, astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space—what they are, rather than where they are", [3] which is studied ...
Burt's solar compass or astronomical compass/sun compass is a surveying instrument that makes use of the Sun's direction instead of magnetism. William Austin Burt invented his solar compass in 1835. The solar compass works on the principle that the direction to the Sun at a specified time can be calculated if the position of the observer on the ...
The history of astronomy focuses on the contributions civilizations have made to further their understanding of the universe beyond earth's atmosphere. [1] Astronomy is one of the oldest natural sciences , achieving a high level of success in the second half of the first millennium.
Heliophysics (from the prefix "helio", from Attic Greek hḗlios, meaning Sun, and the noun "physics": the science of matter and energy and their interactions) is the physics of the Sun and its connection with the Solar System. [1]
Quizlet was founded in 2005 by Andrew Sutherland as a studying tool to aid in memorization for his French class, which he claimed to have "aced". [6] [7] [8] Quizlet's blog, written mostly by Andrew in the earlier days of the company, claims it had reached 50,000 registered users in 252 days online. [9]