He first concieved of the communications sattelite in 1945, and the sychhronous orbits they orbit in are called Clark orbits today.
He wrote the novel/movie 2001, and many other Science-Fiction novels, as well as many purely Science books during his life. He showed the future when it was still unrealized. He overcame Polio as a child and was recovered for many years; only to be stricken by the residual damage as he aged and was in a wheelchair for the last few years.
He could write. He'll be missed.

