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Space suit
A space suit is a complex system of garments and equipment and environmental systems designed to keep a person alive and comfortable in the harsh environment of outer ... > more -
Space exploration
Space exploration is the physical exploration of outer space, both by human spaceflights and by robotic spacecraft. While the observation of objects in space—known as astronomy—pre-dates ... > 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 -
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 -
Star cluster
Star clusters are groups of stars which are gravitationally bound. Two distinct types of star cluster can be distinguished: globular clusters are tight groups of hundreds of thousands of very old ... > 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 -
Stellar classification
In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral ... > 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
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