The maths of the observable universe doesn't add up — until it does.
The observable universe is about 93 billion light-years across. But the universe is only 13.8 billion years old. Light can't travel 93 billion light-years in 13.8 billion years. So what's going on?
Space itself is expanding.
Not like an explosion moving through space — the fabric of space is stretching. Galaxies aren't racing away from us; the distance between us and them is simply growing, carried apart by that expansion.
The most distant light we can detect left its source when the cosmos was very young. In the time it spent travelling towards us, the space behind it kept stretching. That source is now enormously further away than 13.8 billion light-years.
And beyond what we can see? The full universe may be vastly larger — perhaps infinite.
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