Leucippus was one of the earliest Greeks to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms — which was elaborated in greater detail by his pupil and successor, Democritus.This interactive periodic table includes a unique video for each element.

The Cosmic Microwave Background, or CMB, is radiation that fills the universe and can be seen in every direction.

In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system), is a description of the cosmos where Earth is at the orbital center of all celestial bodies. This model served as the predominant cosmological system in many ancient civilizations such as ancient Greece. As such, they assumed that the Sun, Moon, stars, and naked eye planets circled Earth, including the noteworthy systems of Aristotle (see Aristotelian physics) and Ptolemy.

Physicist Patricia Burchat sheds light on two basic ingredients of our universe: dark matter and dark energy. Comprising 96% of the universe between them, they can't be directly measured, but their influence is immense.

Backed by stunning illustrations, David Christian narrates a complete history of the universe, from the Big Bang to the Internet, in a riveting 18 minutes. This is "Big History": an enlightening, wide-angle look at complexity, life, and humanity, set against our slim share of the cosmic timeline.

Supersymmetry is one of the most popular of the speculative ideas that theorists have proposed to understand the puzzle known as the hierarchy problem. It has many wonderful features, ranging from mathematical beauty to its potential ability to explain other puzzles in particle physics, such as the nature of dark matter.