Concept
Celestial Equator
Earth's equator projected onto the sky.
The great circle on the celestial sphere directly above Earth's equator — the dividing line for declination.
Overview
The great circle on the celestial sphere directly above Earth's equator — the dividing line for declination.
See also
Milankovitch Cycles
Slow orbital changes that drive Earth's ice ages.
Celestial Poles
Where Earth's spin axis meets the sky.
The Big Bang
How everything began, 13.8 billion years ago.
Black Holes
Regions where gravity stops light itself.
Dark Matter
The invisible mass holding galaxies together.
Dark Energy
The mysterious force accelerating the universe.