Stephen Hawking was diagnosed with amyotrophic lateral sclerosis (ALS), a progressive motor neuron disease, at age 21. He was given roughly two years to live. Instead, he survived for 55 more years, becoming one of the most celebrated physicists in history, before dying peacefully at his home in Cambridge on March 14, 2018, at the age of 76.
His ALS Diagnosis at 21
In 1963, while a graduate student at Cambridge, Hawking began noticing that he was becoming clumsy. He would trip, his speech started to slur, and he had difficulty tying his shoes. Doctors diagnosed him with ALS, a disease that progressively destroys the nerve cells controlling voluntary muscle movement. Most people with ALS survive two to five years after diagnosis. The prognosis Hawking received was bleak: he likely wouldn’t live to finish his PhD.
But the disease progressed far more slowly than anyone expected. Over the following decades, Hawking gradually lost the use of his limbs and became wheelchair-bound, but his mind remained completely unaffected. ALS destroys motor neurons, not the brain’s capacity for thought, memory, or reasoning. Why Hawking’s version of the disease moved so slowly remains something of a medical mystery. One widely discussed factor is that he was diagnosed unusually young; ALS that appears before age 30 sometimes follows a slower trajectory than typical late-onset cases, though even by that standard, Hawking’s survival was extraordinary.
The 1985 Crisis That Took His Voice
The most dramatic medical turning point came in 1985, when Hawking caught pneumonia while traveling in Geneva. The infection was severe enough to require a tracheostomy, a surgical opening in the windpipe to help him breathe. The procedure saved his life but permanently destroyed his ability to speak. He was 43 years old.
From that point on, Hawking required 24-hour nursing care, funded by grants from several foundations. He would never again speak with his natural voice. For a man whose career depended on lecturing, collaborating, and communicating complex ideas, this could have been the end of his public life. It wasn’t.
How He Communicated With the World
After the tracheostomy, Hawking initially communicated by raising his eyebrows to select letters on a spelling card. Soon after, a computer scientist in California sent him a program that let him select words on a screen, which were then run through a speech synthesizer. That robotic voice became one of the most recognizable sounds in science.
As his condition worsened and he lost the use of his hands, the system was adapted further. Intel developed a platform called the Assistive Context-Aware Toolkit (ACAT) specifically for him. In its final form, a sensor mounted on his glasses detected the movement of a single muscle in his cheek. By twitching that muscle, he could select characters and words on a laptop screen positioned in front of him. Predictive text software built in partnership with SwiftKey helped speed things up by guessing what he wanted to say next. The system then converted his text to speech. Using one facial muscle, Hawking wrote books, gave lectures, sent emails, and browsed the internet.
His Scientific Contributions
Hawking’s most famous theoretical breakthrough came in 1974, when he proposed that black holes are not perfectly black. According to classical physics, nothing escapes a black hole’s gravitational pull. But Hawking showed that when you account for quantum mechanics, black holes should emit a faint glow of particles, now called Hawking radiation.
The basic idea involves pairs of particles that constantly pop into existence throughout space. Normally these pairs annihilate each other almost instantly. But at the edge of a black hole, one particle can fall in while the other escapes. That escaping particle carries away a tiny amount of the black hole’s energy. Over immense timescales, this means a black hole slowly loses mass and eventually evaporates entirely, finishing in what Hawking described as “a blaze of glory like a hydrogen bomb.” The effect is negligibly small for large black holes but was a landmark insight for theoretical physics because it connected gravity, quantum mechanics, and thermodynamics in a way no one had managed before.
From 1979 to 2009, Hawking held the Lucasian Professorship of Mathematics at Cambridge, the same chair once held by Isaac Newton. His 1988 book “A Brief History of Time” sold more than 10 million copies and made him a genuine celebrity, not just within science but in popular culture worldwide.
His Final Years and Death
By his later decades, Hawking was almost entirely paralyzed. He could move only a few facial muscles and relied completely on his nursing team and communication technology. Despite this, he continued publishing papers, giving public talks, and making media appearances well into his 70s. He appeared on “The Simpsons,” “Star Trek: The Next Generation,” and “The Big Bang Theory,” always playing himself.
He also became an outspoken voice on topics beyond physics, warning about the dangers of artificial intelligence, advocating for space exploration as a survival strategy for humanity, and supporting disability rights.
On March 14, 2018, Hawking died peacefully at his home in Cambridge. He was 76. In a coincidence he might have appreciated, the date was also the birthday of Albert Einstein. His ashes were interred at Westminster Abbey, between the graves of Isaac Newton and Charles Darwin.