There have been many scientists, philosophers, entertainers, and scoundrels who, over the last few decades, have taken up the gauntlet of promoting science, tantalizing people with the wonders of scientific endeavour and trying to waft away the ever-present miasma of religion and superstition. Who among them has done the most to promote science, by convincing children to become scientists or shining a light on our ignorance and convincing us it’s better to light a candle and know than huddle in the darkness and pray? Is it Magnus Pike? Bill Nye the Science Guy? Mr. Wizard? Richard Dawkins? Karl Popper? Steven Pinker? Daniel Dennet? The Muppets? Gene Roddenberry? Isaac Asimov? Arthur C. Clarke? Adam Savage and Jamie Hyneman? Gene Ray?!
Remember, we’re not talking about contributions to science itself, but to the promotion of science as a philosophy.
I prefer Gould’s writings, but he seemed to target people who already had a fair amount of interest in science. I’d say Sagan probably did far more outreach type stuff, is better known to the public, and so is the greater promoter.
I’ll go with Carl Sagan also. Having articles in Parade Magazine, and being on Johnny Carson, probably reached more people who needed reaching than all the books of the other people mentioned combined.
Brian Greene (author of The Elegant Universe and host of the NOVA special) deserves mention also. Even if string theory doesn’t live up to the hype, that program does a good job of explaining the basics of modern physics for the lay person.
I would go with Carl Sagan. But I like Bill Nye because he made science understandable and accessible to the general public. But honorable mention would have to be Arthur C. Clarke, Asimov and Captain Kirk and Spock.