Browse Reference Articles
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Geosynchronous orbit
A geosynchronous orbit is a geocentric orbit that has the same orbital period as the sidereal rotation period of the Earth. It has a semi-major axis of 42,164 km (26,200 miles). In the special case ... > more -
Militarisation of space
The militarisation of space1 is the placement and development of weaponry in outer space by the militaries of the ... > more -
Impact crater
An impact crater is a circular depression on a surface, usually referring to a planet, moon, asteroid, or other celestial body, caused by a collision of a smaller body (meteor) with the ... > more -
Earth's magnetic field
Earth's magnetic field (and the surface magnetic field) is approximately a magnetic dipole, with one pole near the geographic north pole and the other near the geographic south pole. The locations of ... > more -
Doppler effect
The Doppler effect, named after Christian Andreas Doppler, is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. The ... > more -
Precession
Precession refers to a change in the direction of the axis of a rotating object. In certain contexts, "precession" may refer to the precession that the Earth experiences, the effects of this type of ... > more -
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 -
International Space Station
The International Space Station (ISS) is a joint project of five space agencies. The ISS has seen the first space tourist, Dennis Tito, who spent 20 million USD to fly aboard a Russian supply mission ... > more -
Presentism (philosophy of time)
In the philosophy of time, presentism is the belief that neither the future nor the past exists. The opposite of presentism is 'eternalism', which is a belief in things that are past and things that ... > more
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