Concept
Redshift & Hubble's Law
The fingerprint of an expanding universe.
Light from receding galaxies stretches to longer (redder) wavelengths. The farther the galaxy, the faster the recession — Hubble's Law.
See also
Dark Energy
The mysterious force accelerating the universe.
Gravity
The force that shapes the universe.
Baryon Acoustic Oscillations
A standard ruler frozen into the early universe.
Reionization Epoch
When the first stars and galaxies relit the universe.
Cosmic Dark Ages
The long pre-starlight era of the universe.
Big Freeze
A possible cold, dark final fate of the universe.