Look at this experiment: Why roll the balls after the collision back to each other? Are they magnetic?
Okay, I've got it now. When I first looked at it, that arrow thingie just didn't quite register in my brain. It took half a dozen more viewings before it did. (I saw it; I just couldn't figure out what it was doing.) Maybe temporal dyslexia affects visual things as well as spoken ones.Look at the sky reflection, right when they collide.
Maybe there's sidespin as well, so they weren't in a visible spot earlier. Originally, once I realized that they were arrows, I suspected that they might have been digitally added to indicate spin, but that doesn't seem to be the case.I'm not sure why I only saw the arrows appear one time ?
I just read the OP's "are they magnetic?", watched once, then read your spoiler, then watched again and it all made sense.Did no one read my spoiler? It describes the arrows.
Thanks, I finally figured it out :) I'm pretty simple minded when it comes to finding text that's not visible. :DI didn't get it at first either, just click and drag the mouse like you are selecting text to copy or quote.
Spoiler! Highliight to read:
The balls are quite dense. They are running on rails, which means they are rotating much faster than their movement would indicate. There's a lot of angular momentum stored.
That angular momentum is not lost when they collide and bounce off each other. In effect, as they move apart, they are "skidding" - they've lost traction, but are still rotating. Eventually the rotation gains traction on the rails and the spheres accelerate toward each other again.
Reviewing the video again, I can see confirmation that I am right. The balls are not perfect; there is an arrow marked on each of them which shows how they are rotating. You can see the arrows in the closeup (as a matter of fact, you can juuuust catch them at the start of the closeup - at 0:19 juuuuust as they disappear into the black reflection at the bottom.) They are rotating the same direction both before and after the collision.