We have a good idea where it comes from: It was created in the big bang, and as stars form (and explode, or form neutron stars and collide) they turn it into heavier elements. Over time there is less hydrogen, which is why the universe can’t be infinitely old. Since it’s only ~13.7B years old, the amount of hydrogen we see makes sense with our models.
It’s a much much bigger problem if the universe significantly older than we think it is… if we were to believe the Wikipedia article on this[0], we’d only expect stars to exist at all for about 100 trillion years, but given that the distribution of hydrogen availability is likely to follow an inverse exponential decay curve of some sort, we’d probably see much lower amounts of hydrogen much earlier than that.
It’s a much much bigger problem if the universe significantly older than we think it is… if we were to believe the Wikipedia article on this[0], we’d only expect stars to exist at all for about 100 trillion years, but given that the distribution of hydrogen availability is likely to follow an inverse exponential decay curve of some sort, we’d probably see much lower amounts of hydrogen much earlier than that.
[0] https://en.wikipedia.org/wiki/Future_of_an_expanding_univers...