Apollo 8 was the first manned space voyage to achieve a velocity sufficient to allow escape from the gravitational field of planet Earth; the first to escape from the gravitational field of another celestial body; and the first manned voyage to return to planet Earth from another celestial body.
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft.
The alkali metals are a series of chemical elements comprising Group 1 of the periodic table: lithium, sodium, potassium, rubidium, caesium, and francium.. The alkali metals provide one of the best examples of group trends in properties in the periodic table, with well characterized homologous behavior down the group.
An alphabet is a standardized set of letters basic written symbols each of which roughly represents a phoneme in a spoken language, either as it exists now or as it was in the past.
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus.
Anatomy is a branch of biology and Medicine which studies primarily the internal structure and design of the structure of living things.
Andrei Arsenyevich Tarkovsky was a Soviet Russian filmmaker, writer and opera director.
Ambiguity is the property of being ambiguous, where a word, term, notation, sign, symbol, phrase, sentence, or any other form used for communication, is called ambiguous if it can be interpreted in more than one way.
The Aardvark is a medium-sized, burrowing, nocturnal mammal native to Africa.
Adobe is a natural building material made from sand, clay, and water, with some kind of fibrous or organic material, which is shaped into bricks using frames and dried in the sun.