OK, having watched this I feel simultaneously really smart/accomplished and also hella stupid. On the accomplished side: I think I grasp the nature of gravity more clearly than I ever have before, and it felt effortless to get there after even just 90 seconds of this video because the commentary and the demonstrating exercise that have been set up here (a giant piece of Lyrca stretched out over a hoop) are just so lucid.
I feel dumb because it took me this long and because the concept isn't that hard....just kind of hard to explain. 24 hours ago I thought gravity was a kind of attractive force that anything in the universe that possesses mass is imbued with. Objects like marbles and people and buildings all exert a pull of gravity on the things around them, but their mass is so small, and their gravity so weak as a result, that it can't be perceived in any meaningful way until you get to celestial sized objects. That is what I thought. And given what the average American learns about physics in high school it's a totally reasonable thing to think. But that is not what gravity is at all. If you are confused watch this video to become confused. If you already knew that then share this video with your confused friends.
The video is apparently a high school/middle school physics teacher at a professional development event with other teachers demonstrating a cool hands-on activity he does each year to explain gravity to his students. It is a very good exercise. I feel smarter. I feel dumber. I'm happy to share those feelings with you. (Warning: there is some *choice* dad humor in here, which, come to think of it, who in the world is more qualified to deliver than a high school teacher wearing Dockers. Thank you Mr. Burns).