What's the best piece of optimistic science fiction?

Science fiction can warn us about potential disasters, and school us about the downsides of knowing too much — but a lot of the best science fiction inspires us, instead, by showing how people can solve problems and conquer ignorance. What's the most uplifting piece of optimistic science fiction you've ever seen?

Please include a picture or clip of your favorite piece of optimistic science fiction. And also please mention the name and why it's so exciting. Thanks!

Top image: Frank R. Paul.