Chapter 09 — Big & Curious
How big is the universe?
The observable universe is about 93 billion light-years across — and that's just what light has had time to reach us from since the Big Bang 13.8 billion years ago. The full universe is almost certainly far larger, possibly infinite.
Follow-up questions
If the universe is 13.8 billion years old, how is it 93 billion light-years wide?
Space itself has been expanding the whole time, stretching the distance light travelled. The photons aged 13.8 billion years; the road behind them grew.
What's outside the universe?
By definition, there's no 'outside' — the universe is everything that exists, including space itself. The question assumes a stage; the universe is the stage.
Is the universe expanding faster?
Yes, and accelerating. The cause is labelled 'dark energy' — a placeholder name for a force we measure but don't yet understand.
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