# If the universe is 13.8 billion years old, how is the observable universe 46.5 billion light years across?

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If the universe is 13.8 billion years old, how is the observable universe 46.5 billion light years across?

In: Physics

Lightyear is a measurement of distance. It’s how long light can travel in one year. One light year is 5.879 × 10^12 miles. It’s an estimate of how large the universe is, not how old it is.

The Universe is expanding, it’s been expanding for billions of years at about this rate. Across the visible Universe, the edges are expanding at a speed greater than the speed of light.

I heard it explained nicely by a loaf of bread rising with raisins in it. The raisins aren’t moving that much compared to the swelling dough between them. Maybe that analogy helps? Otherwise u/WRSaunders is right. Space is itself expanding faster than light can cover the distance.

Light years is a measure of distance and not a measure of time. Hopefully I’m writing enough to warrant a post

Space is big. Really big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist, but that’s just peanuts to space.
*Douglas Adams, The Hitchhiker’s Guide to the Galaxy*