The intent behind my comment was not clear : I dream about stuff which is not frivolous in my opinion. I'd love to see economical nuclear fusion, 2 liters per 100km cars, advanced cancer understanding, interstellar travel. All these things point towards, I believe, a better future (or at least a future with a bit more hope). A supersonic jet doesn't like (for my very novice eyes) a step in the direction of my dreams, hence my question : is there something in it that I should know.