I'm a little confused about Lie derivatives. In fact all that definitions of pull-back and push-forward and one-parameter family of diffeomorphisms and integral curves and so on seems strongly formidable and scary to approach. My question is very simple, I was studying GR from Sean Carroll's book...

This question comes after seeing a video about the SpinLaunch company and their "centrifuge" launch system. As shown in the basic illustration below, a "rocket" shaped projectile will be spun around at very high speeds and then released. Since the projectile is being held so that it's always fac...

By the word spin of elementary particle, one would imagine the particle to be rotating around its own axis, just like a planet rotates, but is it actually true? While spinning does an elementary particle actually rotate around its own axis just like a planet?