Astronomy

The study of celestial objects, the structure of the universe, and the physics of space beyond Earth.

Subcategories

• Planetary Science — Planets, moons, and small bodies of the solar system and beyond.
• Stellar Astronomy — Stars: their formation, structure, evolution, and endpoints.

Articles (3)

• Why Does the Moon Have Phases? A Plain Explanation
  The Moon has phases because the Sun always lights half of it, and our view of that lit half changes as the Moon orbits Earth every 29.5 days, not Earth's shadow.
• Dark Matter
  Dark matter explained: the invisible mass shaping galaxies, the evidence from rotation curves and gravitational lensing, and the hunt for the unknown particle.
• The Big Bang
  The Big Bang explained: how an expanding universe began in a hot dense state, the evidence from redshifts to the microwave afterglow, and what came next.

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