[JAC note: Matthew told me he’d written this draft post and that I could put it up or not depending on whether I liked it. I decided to post it without seeing it, just for the surprise. I predict that the balls will all end up at the bottom, but hat do I know?]
by Matthew Cobb
… you tipped a load of plastic balls onto the bottom of an up escalator. Where would they end up? We’re talking lots and lots of balls. Make your prediction and then click on the video. (And yes, I know the people making the video cheat.) This was posted about 30 months ago – the people who made it (Ian McCart) had a website that no longer works. I think it’s some kind of kinetic artwork.
h/t @cotesia1
I dare say you were wrong, Dr. Coyne! Now we know why you’re not a Professor of Escalators.
My prediction:
The balls are going to get a little push from each escalator step as it rises and all balls will end up at the bottom where they started.
I still haven’t watched it yet, but I thought that the balls would mostly go to the top, but then get hung up at the top where the steps disappear and then bounce back down again.
!! POTENTIAL SPOILER !!
It looked like they were getting hung up at the top, but due to the camera’s position it was difficult to tell exactly why they were just stopping there. I think they had something blocking the balls so they wouldn’t spill into the walkway.
I thought the top too.
Oh man, was I ever wrong.
Very non-linear behaviors look possible, but possibly the ball/escalator universe will reach more or less teady state with the “top” step occupied by balls, and the rest of the balls more or less escaped from the bottom.
(The escalator does keep adding energy to the system.)
Do it long enough and the balls should end up at the bottom. In the video, we can see some escaping at the bottom from time to time, so just do it long enough.
Yikes… didn’t mean to give anything away. Sorry.
I think it would depend on factors such as the number of balls, the size of the balls, the size of the bump at the top, the bouncyness of the balls, and maybe other factors. More balls, bigger balls and a smaller barrier at the top, and many should push off the top. Bouncier balls could escape off the bottom easier. Notice a few balls in the video bounced over the side.
But if you watch the top, someone is up there kicking the balls back down as well. I think this is more about the art of the bouncing balls and less about the physics of where they go.
Sub
Jammed down the perpetrators’ throats by those wanting to use the escalator.
What is especially unexpected are the two guys that come across it near the end, glance at this very strange thing, and walk on without showing any awe and wonder.
I immediately made a guess at their political persuasion. My bad.
Shoot! I thought they were going to sort by color.
That only happens in OCD heaven where the physics and math are way different. All drawers & cupboards close themselves, things follow straight lines, counting stuff is encouraged, even numbers, especially the number 4, are the only numbers & the toilet paper is put on with the flap in the back.
I had a colleague who had their desk organized like that. Everything was perpendicular or parallel. One day I peeked into the top drawer of their desk and saw that every paper clip was stacked perfectly, one on top of the other.
You do know that people with OCD tendencies are suggestible, don’t you?
I resist your power to control me! Actually focussing hard on not doing such things can make it more likely to get stuck in.
Your colleague’s desk has toilet paper?! Now that is innovation!
I thought there was an equal chance they could be at the bottom or the top. Did not expect such an even distribution, also did not expect it to be so beautiful.
I wouldn’t say they cheated, as such, but I still can’t say I know how it ended and still can’t guess. It would be nice to see it in sequence and in full.
Also unexpected: a weekend post about balls that is up for half a day and no testicular puns! Classy!
Finally! Something I could figure out. They looked about the weight of a Whiffle ball and I knew they wouldn’t make it over the top.
Haven’t watched it yet, but it seems clear that no individual ball can come to rest while it’s still on the moving escalator. So to end up somewhere it must get off either at the bottom or at the top. A ball bouncing down the stairs can easily bounce clear at the bottom, but to get clear at the top requires a rising tide of balls behind it to push it clear. So my prediction is that most balls end up scattered around the bottom of the escalator, with at most a handful at the top.
Spoiler!
Well, there is quite a pileup at the top, but the camera angle doesn’t let us see if any balls are being pushed clear. A few balls do bounce back down with enough energy to escape at the bottom. But it looks like the vast majority are still in play, not having come to rest anywhere, when the experiment ends and the balls are collected. So I’m calling it inconclusive, unless you want to count bouncing around near the top as “ending up” somewhere.
This reminds me vaguely of a problem from my freshman physics course many, many years ago.
Imagine a closed room, the floor of which is covered wall to wall with armed mousetraps. Each mousetrap has a pingpong ball balanced on its spring arm. You open the door a crack, toss it one more pingpong ball, and close it again. Derive an equation that predicts the number of balls in the air as a function of time.
I would like to express my opinion on this, since I’m both an atheist and I find myself having frequently low moods or some feeling of dissatisfaction.
One thing I know for sure: it’s not being atheist that makes me unhappy, quite the contrary, the fact that I’ve stopped to believe in gods and religions is kind of a relief for me. I call it one of the best decision of my life – or better yet – the best series of decisions, since the whole transition from 100% catholic to 100% atheist was very progressive and did happen over the course of many years. From when I embraced the idea that there’s nothing supernatural in this world, i got this feeling that “everything fits together” that I always missed when I was a believer. And this is a LIBERATING thought!
The only thing that I could concede is that my atheism and my bad moods are indeed correlated, in the sense that they are both the product of a common cause. I’m not an expert in psychology or cognitive science, but it seems to me that my “cognitive style” or something like that pushes me to be both atheist and melancholic.
Of couse I commented on the wrong post. I’ll repost it on the correct one, feel free to delete this entry.
Jerry would probably have been correct, but the voices (and the light!) in the vid suggest the experiment was conducted in the southern hemisphere where everything is backwards.
Last year when in Japan on a language course, a fellow resident of Australia told us, quite seriously that since we were in the Northern hemisphere that the sun rose in the West. The really scary thing is that that person’s job was advising people on installation of sola panels!!
My expectation would have been a distribution with the maximum in the lowest (potential) energy state at the bottom and decreasing numbers lifted to each level. But that rather depends on there being something to stop the balls escaping at the bottom, and enough random motion in each ball as it gets lifted up to form the first step that they’ll remain on that step for long enough that some will proceed to higher steps.
But I’d also bet that the “artists” would likely cheat by gluing little magnets into each ball, helping some to stick onto the steps and be collected at the top. (oh yeah ; the colours would be distraction.)
[Watches] Hmm, there’s something taking energy from the system. Unless those balls are a lot less squashy than they look. Anyway, volcanic rocks of North Fife this morning, unless the snow covers up the rocks. So I’d better go.
I read your comment while posting. Your observation of dissipation could concur with my analysis below, rolling friction could be the main culprit.
Oops! I forgot to make a prediction before watching the video. :-/
But anyway, this could make for a nice problem. The resulting steady state could depend on the escalator speed vs the ball speed, so ball size and mass. One could approximate the escalator with a moving sloping plane, and possibly the rolling frictions for the balls gets into it.
[I assume one could neglect hops for simplicity by shrinking the step height and length proportionally until rolling, as well as the collisions by diluting to a sparse set of balls.]
But I feel too lazy today…
“rolling friction”. Don’t know where that “s” came from, especially if one wants to make a simpler problem…
Seems like a good conceptual metaphor for deistic/theistic/cosmic evolution, with g*d as the escalator.
The balls appear to accumulate at the top, where they are (presumably) prevented from exiting the system. However, they are not prevented from exiting at the bottom, and periodically a ball has enough energy to roll or bounce away (one even bounced over the railing onto the adjacent escalator). In time there will be fewer balls, and my guess is eventually only those stuck on the top floor would remain. I wonder:
1. what would be the distribution of balls in the system if both ends where blocked?
2. just the bottom were blocked?
3. neither end was blocked?
4. what would be the result if the balls were released from the top?
5. what would be the result using ping pong balls or nerf balls or marbles or bowling balls(!)
I loved the couple walking up to use the escalator. with the ‘WTF are you doing?’ expression on their face.