Evolution of String Theory and Particle Study in Physics

Stephen Wolfram answers questions from his viewers about the history of science and technology as part of an unscripted livestream series, also available on YouTube here: https://wolfr.am/youtube-sw-qa

Questions include: Can you talk about the history of gazettes, i.e. the recording of "official" information? - Why are some older coins or bills worth more than their original face value? - ​How does Galileo's equivalence principle relate to Einstein's equivalence principle? - ​Important work from bright minds gets shelved, and then we discover the work decades later and put it to use. Have you thought of ways to reduce this happening so much? - Could you elucidate the historiographical development of string theory, assess whether its inception was exclusively within the mathematical domain, and determine if it has yielded any tangible technological advancements? - Some old things are worth more due to nostalgia. Eventually, they will lose their value again. - What is the history behind observer theory?