By the Gregorian calendar now used worldwide, Isaac Newton was born on January 4, 1643 (he was born December 25, 1642, under the Julian calendar then in use in England). The fatherless, sickly infant grew into the towering figure of the Scientific Revolution, formulating the laws of motion and universal gravitation that would define physics for over two centuries.
Newton arrived so early and so frail that servants at Woolsthorpe Manor did not expect him to survive the night. His father, a yeoman farmer, had died three months earlier, and his mother Hannah would later remarry and leave young Isaac to be raised by his grandmother — an abandonment some biographers believe shaped his famously guarded, solitary temperament.
The date itself is a small historical puzzle: England did not adopt the Gregorian calendar until 1752, so Newton's contemporaries recorded his birth as December 25, 1642, a coincidence with Christmas that later admirers found irresistible. Converted to the modern calendar, the date shifts to January 4, 1643.
That unpromising infant would go on to write the Principia Mathematica, invent calculus (alongside Leibniz), and serve as Master of the Royal Mint. He also spent years pursuing alchemy and biblical chronology, reminding us that the father of modern physics lived comfortably alongside pursuits we now consider pseudoscience.
Key people: Isaac Newton