This is really an excellent text about special relativity. Physicists might consider this too imprecise and informal. But I think it’s exactly right for an intr

This is really an excellent text about special relativity. Physicists might consider this too imprecise and informal. But I think it’s exactly right for an introducing. So if you have a 15 year old who is interested in that topic, this might be a start. I remember that it took me a while to understand that a constant speed of light means that time and space need to adapt so that the physics stays correct. I haven’t seen special relativity explained so clearly. Not to mention the piece of science history to tell people how messy scientific progress can be.