How Stephen Hawking’s wheelchair works
Stephen Hawking was diagnosed with amyotrophic lateral sclerosis (ALS) when he was 21. ALS is a form of motor neurone disease, which results in the progressive death of the nerves that control the muscles. Most sufferers die within five years, but fortunately for physics, and for Professor Hawking himself, his disease has progressed extremely slowly. Even so, at the age of 73, Hawking has just a small amount of motor function left, mainly in the muscles of his face. His link to the world is provided by the computer technology built into his wheelchair.
Incredibly, Professor Hawking controls all the functions of his Windows tablet PC using just a single switch – imagine operating your PC using nothing but the spacebar! Hawking’s PC uses a special interface called EZ Keys, which scans across each letter of the on-screen keyboard, one at a time. When Hawking moves his cheek, a sensor detects the movement and the computer halts the scanner and picks that letter. He can also use this process to scan from one button or menu item to the next, and so control his email program (Eudora), web browser (Firefox) or even make calls over Skype.
As Hawking’s physical condition gradually deteriorates, his typing speed has dropped to just one or two words per minute. Scientists at Intel compensate using algorithms tailored to Hawking’s vocabulary and writing style, which accurately predict which words he will want to use next.
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