Science
What is the Universe?
The universe is everything that exists — all of space, time, matter, and energy, from the tiniest particle to the largest galaxy. It began about 13.8 billion years ago in the Big Bang and has been expanding ever since.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains the universe.
Key things to understand
- 1The universe is all of space and time and everything in it — galaxies, stars, planets, matter, and energy.
- 2It began roughly 13.8 billion years ago in the Big Bang and has been expanding outward ever since.
- 3It contains hundreds of billions of galaxies, each with billions of stars.
- 4Most of it appears to be invisible 'dark matter' and 'dark energy' that we detect only through their effects.
- 5The observable universe is about 93 billion light-years across, but the whole may be far larger.
Frequently asked questions
- How big is the universe?
- The observable universe is about 93 billion light-years across. The full universe may be much larger — possibly infinite — but we can only see the part whose light has reached us.
- How old is the universe?
- About 13.8 billion years, measured from the Big Bang — the event from which space, time, and matter as we know them began.
- Is the universe still expanding?
- Yes, and the expansion is speeding up. Galaxies are moving apart, driven by a mysterious effect attributed to 'dark energy'.