Browse Reference Articles
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Torino Scale
The Torino Scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and ... > more -
Model rocket
Model rocketry is a hobby similar to building model airplanes. In the hobby today, there are two distinct areas of rocket activity: amateur (or experimental) rocketry, and model rocketry (including ... > more -
Black hole
A black hole is a concentration of mass great enough that the force of gravity prevents anything from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). The ... > more -
Shape of the Universe
The shape of the Universe is a subject of investigation within physical cosmology. Cosmologists and astronomers describe the geometry of the Universe which includes both local geometry and global ... > 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 -
Gravitation
Gravity is a force of attraction that acts between bodies that have mass. Gravity is the reason for the very existence of the earth, the sun and other celestial bodies; without it matter would not ... > more -
Water rocket
Water rockets are like their model rocket cousins, except that these are powered by a combination of water and air pressure instead of a chemical propellant. The pressure vessel, the engine of the ... > more -
General relativity
General relativity (GR) is the geometrical theory of gravitation published by Albert Einstein in 1915. It unifies special relativity and Sir Isaac Newton's law of universal gravitation with the ... > more
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