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Introduction to general relativity
General relativity (GR) is the geometrical theory of gravitation published by Albert Einstein in 1916. It unifies Einstein's earlier special relativity with Sir Isaac Newton's law of universal ... > more -
Exploration of Mars
The exploration of Mars has been an important part of the space exploration missions of the Soviet Union (later Russia), the United States, Europe, and Japan. Dozens of unmanned spacecraft, including ... > more -
Saturn's natural satellites
Saturn is currently known to have 56 moons, many of which were discovered very recently, and 3 additional un-confirmed, hypothetical moons. However, a precise number of moons can never be given, as ... > more -
Space elevator
A space elevator is a theoretical structure designed to transport material from a planet's surface into space. Many different types of space elevators have been proposed. They all share the goal of ... > more -
Space debris
Space debris or orbital debris, also called space junk and space waste, are the objects in orbit around Earth created by man that no longer serve any useful purpose. They consist of everything from ... > more -
Compton Gamma Ray Observatory
The Compton Gamma Ray Observatory (CGRO) was the second of the NASA "Great Observatories" to be launched to space, following the Hubble Space Telescope. The observatory was launched on the Space ... > more -
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and ... > more
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