You know like the kind that go on a window or bathroom mirror or on the wall or in the shower. They need the atmosphere pushing down on them to work, right?
Yes. They won’t work because they operate on a difference in air pressure providing a force. No air? No force. Same reason an airplane wing won’t provide lift in the upper atmosphere.
But, compare to a rocket engine that does NOT need an atmosphere to push against.
This only works on “virgin” metal iirc - if it’s been exposed to Earth’s atmosphere, it won’t work. If you shave off some from the surface I believe it works again.
I didn’t realize that the layer was thin enough to rub away with minimal friction. I’d learned about this years ago so I could be misremembering things, but the source I read made it out as if it wasn’t a major concern with space exploration because it took substantial effort to cold weld things that had been exposed to air.
I like the gauge block notion. A (quick) search says that it’s a combination of surface tension from the oils they’re coated in, suction (gone for us), and the super flat surfaces slightly exchanging electrons and bonding in close proximity.
I’m a fan of the surface tension angle as the “rocket of suction cups”, since it’s got that “non-binding force” element, where welding or glue feels different, and Velcro feels like a tangle.
It’s “pull-y” where suction is “push-y”.
Now the question is would surface tension grab something in a vacuum the way it does outside of one. I know you’d have water sublimate off, so it’s questionable to me.
Just a technicality, but the Casimir effect would still provide some adhesive force. It would be greatly reduced vs a suction cup in an atmosphere, but it wouldn’t be 0 force.
Though in microgravity, it might be enough to stick something to a surface, as long as it’s not getting bumped or jostled. And don’t expect it to stay in place if you need to do a maneuvering burn.
Ah thanks for the spelling, swipe typing had Kashmir already so I thought that was right. Corrected above.
And yeah, even in high school I was lucky to have a physics teacher that liked delving deeper into the topics than what’s normally done at that level because my mind seems to naturally seek out those edge cases where rules as given break down. Still hoping we find one of those cases for the laws of thermodynamics lol.
It’s a good line of thinking for trying to be scientific (how do we replicate conditions better, and where might we be introducing errors that would make the experiment “bad”), so you didn’t deserve a down vote.
That being said, it won’t change the outcome too much. In a vacuum, it’s just pushing a bit of rubber against something, there’s no possibility for suction. It’ll just fall off.
If it starts outside a vacuum, the force of air pushing on the outside will keep the rubber from pushing away from the surface at first, but as the air pressure drops, the little bit of air under the cup will give it the tiniest oomph of extra push as it falls off in a way visually indistinguishable from the vacuum scenario.
That’s what I was thinking too, you would need to have the pressure outside the cup to be higher, that’s the force keeping the cup “sticking”.
My prediction is that if you were to stick the cup while under atmospheric pressure, it would have a small amount of air inside … making it unstick more easily after the outside gets depressurized, compared to the condition of having stuck the cup while in vacuum, although the difference would properly be negligible.
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