The Climbing Magnets Mystery (ft. Steve Mould)

When spun on a screwdriver, magnets climb up its length, but why?

This all started with a question on twitter, when someone wanted to know why a chain of neodymium magnets climbs up a screwdriver when the screwdriver is rotated. A search for the explanation ensued, culminating in the stick-slip conclusion presented in this video. Let us know what you think in the comments.

[Dodo-rbzf]

ME "Well that's easy to answer..."
Steve "If you turn upside down, it still goes up"
ME "Alright... I still a dumb mf"

[mauritz]

Why is this on 2veritasium and not on the main channel?
Steve Mould is High quality content!

[PaulPaulPaulson]

In my head, I was already constructing a complicated device to spin it with a smaller radius at the top. Then Steve just turns the screwdriver upside down. Now i feel stupid 😁

[LookingGlassUniverse]

Such an exciting collaboration! And really intuitively explained too- well done ☺️

[gorisenke]

The only think I can think of (haven’t heard their explanation yet) is that magnetic fields have a flow, I think it’s clockwise, that they are acting in. It’s the same reason railguns work, you wind your electromagnets in a way where both magnetic rails have a flow that goes forward towards the tip, and the ammunition is launched that direction. Here, the forces aren’t as extreme, and the magnets don’t have anything to suspend them in open space, so friction stops them from moving, but by spinning it, you’re adding another velocity than just towards the rod, and the magnetic field’s flow makes them roll forward. My thought starts crumbling there though. Dunno if it’s friction that lets it go up, I’m just thinking that the magnets roll and maybe this is why.

Edit: well shit I was waaaay off.

[mikerich]

But in order to be certain this theory is correct, it needs to be tested with different variables. For example, magnets with a square cross section instead of a circle, or a change in relative size in either the metal pole (screwdriver) or the magnets to test the "roll and slip" idea.

[akshat]

I love Steve so much. He explains everything so nicely and elegantly that even a 5 year old would understand after a while.

[jadeddragoon]

4 seconds into video... "uhm... centrifugal force? How is that not obvious?"
1:00 into the video... "oh... okay... never mind then..."
5:30 "Ooooh! Because gravity! Okay."

[kart]

Marvel: "Avengers Infinity War is the most ambitious crossover event in history"
Veritasium: "hold my beer."

[omri]

You can demonstrate it by drawing a line with a marker over the magnets and do a short spin to check it it rotated the way you predicted.

[ClearerThanMud]

Wow! I was expecting this to be a fairly lame video boiling down to the tilt of the screwdriver, but I WTFed when he did it upside-down. The stick-slip explanation is gorgeous and unexpected.

This video makes me want a new adjective meaning "seemingly lame at first glance but surprisingly interesting." :)

[DerUnbekannte]

what a fantastically calming way of speaking

[kronk]

Steve is really awesome. He has the most easy to understand explanations Ive seen.

[danieljensen]

Isn't it general relativity and quantum mechanics that don't get along? I'm pretty sure QFT and even the Dirac Equation are perfectly happy with special relativity...

[markjones]

Throughout the video, everything I came up with a counter point he almost immediately explained it to my satisfaction. Cool video, thank you. It's always a good day when I can learn something new.

[dWHOHWb]

Well, since there's no symmetry and gravity always biases it upwards... And as it moves around the screw driver, gravity is tipping the magnet roll downwards, only the bottom edge makes good contact and the strip rolls around its end. And it'll have a turning radius pointing upwards, since the "inside" of the turn is always pointing up thanks to gravity. Kind of like if you take a core of a toilet paper roll or any other cylinder, stand it up on its end on a flat surface and apply a fake "gravity" to the top, tangential to the flat surface thereby tilting the cylinder... If you then push the cylinder along such that it rolls on the remaining edge, it'll tend to translate on the surface away from the direction "gravity" is pointing in.

That was my thought anyway, before you pointed out the noise -- though I still think it would work just as well even if it could not slip.

[davelangford]

Steve Mould has the best science channel on Youtube. I love the way he explains things

[unvergebeneid]

Yep, Steve Mould definitely deserves more subscribers!

[JaapvanderVelde]

Almost wrecked my headphones trying to correct the missing audio channel on Derek, but then Steve came one. Thanks Steve!

[pjox]

You should have posted this to your main channel. This is a very simple yet very well done video. You could've given Steve far more visibility like that!