Irish mathematician, astronomer & physicist William Rowan Hamilton was born #OTD in 1805.
Hamilton made his discovery of the algebra of quaternions in 1843. His work is fundamental to modern theoretical physics, particularly his reformulation of Newtonian mechanics. Hamiltonian mechanics including its Hamilitonian function are now central both to electromagnetism & quantum mechanics.
https://en.wikipedia.org/wiki/William_Rowan_Hamilton
Books about William Rowan Hamilton at PG:
https://www.gutenberg.org/ebooks/search/?query=William+Rowan+Hamilton&submit_search=Go%21