times in the past have been a lesson of touch and go. the frequency of such occasions is likely to increase in the future. we shall need great care and judgment to negotiate successfully, but i'm an optimist. if we can avoid disaster for the next two centuries, our species should be safe as we spread into space. >> cnn's samuel burke live with us from london. that voice, that synthesized voice, one of most recognizable on the planet. how will he be remembered? >> reporter: good morning, dave. without a doubt in the science world he'll be remembered for merging the theory of relativity from einstein with quantum theory that basically said the beginning of space and time, it starts with the big bang but ends with black holes. even if you didn't understand the science, what inspired so many about this man is he was diagnosed with als in 1963 and given only a few years to live.