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Dark energy
In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Assuming the existence of dark energy is ... > 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 -
Aurora (astronomy)
The aurora is a glow observed in the night sky, usually in the polar zone. It is also known as "northern lights" or "aurora borealis," which is Latin for "northern dawn" since in Europe especially, ... > 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 -
Physical cosmology
Physical cosmology, as a branch of astrophysics, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. Cosmology ... > more -
Militarisation of space
The militarisation of space1 is the placement and development of weaponry in outer space by the militaries of the ... > more -
Interstellar medium
The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. Whilst the ISM refers to the matter (interstellar matter, also abbreviated ... > more -
Open cluster
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud, and are still loosely gravitationally bound to each other. In contrast, globular ... > more
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