How do you know when a particle is going backwards? Is it when it doesn't start in the center, or the line is curved?
by ElisabethB moderator
Hi clarebearthe1st and welcome to HH
That is a really difficult question !
For instance in this image the two white lines at 5 o'clock intersect, but here I would say that the lines going back to the centre are backtracks. So I wouldn't mark this as an ocv. Hope this helps a bit! 😄
Happy hunting !