Concept
Light-Year & Astronomical Distances
Measuring the unimaginable.
A light-year is the distance light travels in one year — about 9.46 trillion km. Astronomers use it (along with AU and parsec) because metres are useless across cosmic scales.
See also
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.
Gravity
The force that shapes the universe.
Redshift & Hubble's Law
The fingerprint of an expanding universe.