What’s the distance to the farthest things we can see?
Our sight limit defines a sphere with us at the center – we call it “Observable Universe”. But how big is it? The universe is 13.8 billion years old, so the furthest things we can see are those whose light has been travelling for 13.8 billion years. Does the Observable Universe have a radius of 13.8 Bly, then? Well, not quite – since the Universe is expanding, those 13.8 Bly have now become about 3 times larger – some 45 Bly. That's the size of the Observable Universe – for now!
Kurzgesagt – In a Nutshell
What’s the distance to the farthest things we can see?
Our sight limit defines a sphere with us at the center – we call it “Observable Universe”.
But how big is it? The universe is 13.8 billion years old, so the furthest things we can see are those whose light has been travelling for 13.8 billion years. Does the Observable Universe have a radius of 13.8 Bly, then? Well, not quite – since the Universe is expanding, those 13.8 Bly have now become about 3 times larger – some 45 Bly. That's the size of the Observable Universe – for now!
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