> So the greatest physics, maths, poetry and pop music are done by people in their 20s.

I can, just from feeling, agree to the pop music. About math I would cite the example of Gilbert Strang, who made many books at advanced age, including one at age 86 or other publications well over the 70s. Another example (well not math, but CS) Donald Knuth. I do not know how is the whole statistic, but writing good books, even text books, does not seem to be teenager thing.