I happened to encounter an interesting phenomenon in candle wax. As shown in the video, small dust near the fire seem to move back and forth, as if there is some kind of repulsive and attractive force. What is the cause of this motion? Thanks.

My question is: Does angular momentum conservation considerations alone forbid a spin-1/2 particle from decaying into two spin-1/2 particles? According to this stackexchange post, the answer seems to argue that you cannot add two spin-1/2 particles and get a spin-1/2 particle. Yes, I understand ...