There is this old adage that says something like: if you have not made your mark in Physics by the age of 30 then you are not going to.
Of course, I presume that other areas of study could be substituted for "Physics". But, when I was an undergrad Physics major in the latter half of the 1960s, this was often heard among students thinking about their future in Physics and wondering if they will "make it by 30".
But, where did this come from? That is my question.
In looking at the major players of the first part of the 20th century physics scene who are known for major breakthroughs we have: Planck age 30 in 1900 when he published his work, Einstein age 26 in his miraculous year of 1905, Bohr was 28 when he published his atomic "Bohr Model" in 1913, de Broglie was 31 in 1923 when he published his work on particle-wave duality, Heisenberg was 24 when he published his "Matrix Mechanics" in 1925, Schrodinger was 39 during his 1926 publication of wave mechanics, Max Born was 45 when he published about "Probability Waves" in 1927 and Paul Dirac was 26 when he published his Electron Theory in 1928.
So, a list of 8 well known physicists who definitely made a mark for themselves in Physics but only half of them were 30 or under in age. And, two of them were in their 40s (old men!).
I am curious -- who says you need to be younger than 30. I am hoping there is still hope for this 69-year old.