It doesn't, but in a way it's treated as a geographical name, same as names of stars, planets, or for example "Droga Mleczna" (Milky Way). Moreover, we only know one Universe, so it makes more sense to capitalize it.
While it's logical, I've never seen it capitalized in English. It's certainly not a big deal, though.
When you're asking about age for other things, like a cake or a baby, do you just change years to something more suitable, like days, months etc, or is there another way to ask how old something is?
Indeed, you just change years to something else:
- „Ile dni ma [cośtam]” – '(lit.)How many days [something] has' – Could be asked for example about suspicious yoghurt you just found in your fridge
- „Ile miesięcy ma [cośtam]” – '(lit.)How many months […]' – Frequently used to inquire about the age of babies
- „Ile wieków ma [cośtam]” – '(lit.)How many centuries […]' – Age of trees, objects in museums and so on