20 Interesting Facts That Prove You Don’t Know Much About Isaac Newton

While we celebrate Newton for his work on gravity and calculus, he actually devoted decades to alchemy. His obsession was intense: he wrote more than a million words on the transmutation of metals and the search for the philosopher’s stone. Traces of mercury from these experiments were even found in his hair several centuries later.

Newton once pushed a blunt needle between his eyeball and his eye socket, just to see what would happen. The pressure he applied caused colorful circles and spots to appear, which helped him understand how vision actually works.

When Leibniz challenged Newton’s claim that he had invented calculus, Newton did not play fair. As president of the Royal Society, he formed an “impartial” committee to investigate, then secretly wrote the report himself. The verdict? Leibniz was found guilty. European mathematicians were divided into two camps for decades afterward.

At the age of 50, Newton suffered a complete mental breakdown that lasted about 18 months. Insomnia tormented him, while paranoid delusions convinced him that his friends were conspiring against him. He wrote accusatory letters that he later regretted. Historians suspect that mercury poisoning resulting from alchemical experiments triggered this breakdown.

Although he had proven that comets obeyed the laws of gravity, Newton privately regarded them as coded warnings from God. His studies of biblical prophecies linked these celestial visitors to apocalyptic disasters and wars. He had even calculated that the world would not end before 2060.

Newton embarked on a full-scale crackdown on counterfeiters. He personally interrogated criminals, gathered evidence, and testified in court, viewing counterfeiting as treason. His relentless pursuit led to William Chaloner’s execution in 1699. Newton even went so far as to infiltrate London’s criminal underworld.

Thousands of pages written by Newton remained hidden for centuries because they contained heretical ideas. He rejected the doctrine of the Trinity, but encoded his anti-Christian views using anagrams and symbols to avoid persecution. These explosive manuscripts were not fully revealed until the 1900s.

Parliament got practically nothing out of Newton. Throughout his term as a representative of the University of Cambridge, he remained silent during debates and offered no ideas. His only recorded comment? Asking someone to close a window that was letting in a draft.

Newton made 7,000 pounds (about 1.5 to 2 million U.S. dollars today) by selling his shares in the South Sea Company early on, but then, overcome by greed, he reinvested it all. The bursting of the bubble in 1720 cost him at least £20,000 (about 4 to 5 million U.S. dollars today). His famous quote in hindsight: he could calculate the movements of the heavens, but not human folly. Finance courses still quote this phrase today.

Robert Hooke, Newton’s fierce rival, claimed credit for ideas on optics and gravity. Rather than face criticism, Newton kept his manuscript Opticks in a drawer for years. Upon Hooke’s death in 1703, Newton published it. He also removed Hooke’s name from subsequent editions of the Principia.

After his stepfather’s death, Newton’s mother took him out of school at age 14 so he could run the family farm. He was terrible at it, spending his time reading instead of tending to the sheep. His uncle finally convinced his mother to send him back to school.

Public confrontations terrified Newton. After critics attacked his theory of light in 1672, he threatened to stop publishing altogether. He avoided direct debates and let his supporters fight his battles for him. Yet, behind the scenes, he relentlessly pursued his claims to priority through institutions he secretly controlled.

Newton’s obsession with optics led him to stare directly at the sun through mirrors for long periods of time. His vision then deteriorated: persistent spots and color distortions plagued him for days. He shut himself away in a dark room to recover, yet still documented this dangerous experiment.

Queen Anne knighted Newton in 1705, but not for discovering gravity or revolutionizing mathematics. His title was a reward for his years of public service spent reforming the currency and tracking down counterfeiters as Master of the Mint. His scientific genius alone was not enough: it was by pursuing criminals that he earned the title “Sir Isaac.”

His library was filled with books on Hermeticism, Kabbalah, and occult philosophy. Newton actively collected and annotated these magical works, viewing them as sources of hidden ancient wisdom. He owned more occult books than many professional magicians.

Newton held the prestigious Lucasian Chair from 1669 to 1702, but students regularly skipped his lectures. He would sometimes walk into completely empty lecture halls and deliver his lecture anyway, just to fulfill his contractual obligations. Teaching bored him: his personal research in his cluttered rooms was far more important to him.

Newton rejected purely mechanical explanations of gravity. His private writings suggest that he viewed the force of gravity as God’s active will holding the universe together. In later editions of Opticks, he hinted that invisible forces might stem from divine rather than material causes.

As a teenager, Newton once threatened to burn his mother, Hannah, and his stepfather, Barnabas Smith. His private list of sins documents this violent rage, as well as his confessions regarding the beatings he inflicted on his sister and the theft of plums. Family resentment ran deep after Hannah remarried and abandoned young Isaac.

Newton shut himself away in a dark room at Woolsthorpe Manor, with only a tiny beam of light and a prism for company. For months, he hardly ever left the room, obsessively studying how white light breaks down into colors. His experimentum crucis with two prisms proved that colors were fundamental.

John Flamsteed, the Royal Astronomer, refused to hand over the lunar observations that Newton desperately wanted. Newton retaliated by using the power of the Royal Society to seize Flamsteed’s data and publish it without authorization in 1712. Flamsteed fought back in court and literally burned copies of the unauthorized edition.