Changes

* '''19''' - [[Evariste Galois]] develops [[group theory]], and wrote it out completely on the eve of his death at age 20; it took old [[mathematicians]] a century to comprehend it.

* '''19''' - [[Evariste Galois]] develops [[group theory]], and wrote it out completely on the eve of his death at age 20; it took old [[mathematicians]] a century to comprehend it.

* '''19''' - [[John D. Rockefeller]] starts a new company, turning an enormous profit in its first year, and became the most influential businessman in history.<ref>http://www.notablebiographies.com/Pu-Ro/Rockefeller-John-D.html</ref>

* '''19''' - [[John D. Rockefeller]] starts a new company, turning an enormous profit in its first year, and became the most influential businessman in history.<ref>http://www.notablebiographies.com/Pu-Ro/Rockefeller-John-D.html</ref>

* '''19''' - Mark Zuckerberg develops Facebook, the leading social networking system for young people on the [[internet]]

* '''19''' - Mark Zuckerberg develops Facebook, the leading social networking system for young people on the [[internet]].

* '''20''' - Carl Friedrich Gauss makes his first mathematical discoveries, which will lead to the completion of "Disquisitiones Arithmeticae", his magnum opus, at the age of 21.

* '''20''' - Carl Friedrich Gauss makes his first mathematical discoveries, which will lead to the completion of "Disquisitiones Arithmeticae", his magnum opus, at the age of 21.

* '''20''' - Willis Carrier invents air conditioning

* '''20''' - Willis Carrier invents air conditioning.

(add more, sorted by age and then alphabetically)

(add more, sorted by age and then alphabetically)