Renowned physicist Stephen Hawking has been living with amyotrophic lateral sclerosis, or ALS, for for 51 years; he was diagnosed at age 21. ALS is the progressive degeneration of motor neurons, which leads to muscle weakness, and can result in paralysis, difficulty, speaking, breathing or swallowing, and eventual death.

Prior to this summer, there was little awareness for this disease, which currently affects around 30,000 Americans.

This awareness was in part due to the viral philanthropy craze, “ALS Ice Bucket Challenge.” The challenge, spread rapidly through social media, and raised over $100 million for the ALS Association.

This week, Stephen Hawking took the challenge. In his video, the professor urged viewers to donate to the Motor Neuron Disease Association, to help “eliminate this terrible disease.” Watch below: