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Is this the Casimir effect? https://en.wikipedia.org/wiki/Casimir_effect
1. pull apart an old multi-platter hard drive
2. Take the platters out
The platters are very flat, and they stick together remarkably well without any liquid between the surfaces. Specks of dust will stop them sticking together so well.
Be careful not to breath in any dust (or eat anything!) from the drive, as they do contain some exciting elements.
Great stuff. We need more of these types of science tidbits on HN. And good links by the commenters too. I love Feynman's classic style of "explaining to a 5 year old" on Cold Welding. The reason for this unexpected behavior is that when the atoms in contact are all of the same kind, there is no way for the atoms to “know” that they are in different pieces of copper. When there are other atoms, in the oxides and grea…
This doesn't really apply to gage blocks because tool steel has passivated surface oxides and complex crystal structures. There are very few metallic bonds exposed on its surface. It also has very nasty, often needle-like grains. There's no chance that the metal atoms are being attracted to each other. Not to mention that wringing works with ceramic gage blocks as well.
It is probably a complicated combination of effects. Adhesion (intermolecular forces) probably plays a minor effect at small regions where the surfaces are extremely close together. Casimir forces probably have an effect on most of the surface. Small amounts of grease probably form much stronger adhesions by "carrying" the forces between the surface oxides. Vacuum being trapped by grease probably plays a fairly large part in rougher blocks wringing in an atmosphere. Adhesion and Casimir forces are not well understood.
This is part of the reason why you commonly see cymbal players in orchestras use an oblique motion for a crash rather than a head-on direct motion. Bringing two symbols together directly along their axis of rotation risks getting them stuck together like suction cups--the crazy part is that even when holes are drilled to release the near vaccum between two stuck cymbals, they remain glued together by the forces descr…
Are you sure that's not just the air pressure difference? Cymbals often have a shape with many concentric ripples, so you might need multiple holes to equalize the air pressure between each ripple. Wringing only works with extremely flat surfaces, and it works even in vacuum.
I grew up next to an abandoned granite quarry. You could, and still can --though they are beginning rarer as the quarry is a bit of a tourist attraction, find super smooth, polished rocks. We would do this wringing with them all the time as kids. Never over until now did I wonder if anyone else had ever done this or if it had a proper name.
I feel like the article is missing a section on uses. Is it strictly measurement?
You can use them in concert with a Sine bar to create precise angles https://en.wikipedia.org/wiki/Sine_bar
[1] https://www.nist.gov/sites/default/files/documents/calibrati...
Further more, if you're really interested in how modern precision engineering/industrial manufacturing came to be; I highly highly recommend you look into Foundations of Mechanical Accuracy by Moore. (it's a $150 book, pdf easily found by googling.)
(I'm a flatness/metrology nerd. I recently lapped three cast iron plates together just because I wanted to create as flat a surface as I could. Just because. )
Almost all you'll ever need to know about gauge blocks [1]. It's also a fairly decent introduction to the uncertainties of measurements, and other factors of taking measurements of objects. Of course it also includes a section on wringing. (and other sources on papers about the wringing phenomenon) [1] https://www.nist.gov/sites/default/files/documents/calibrati... Further more, if you're really interested in how mod…
Great stuff. We need more of these types of science tidbits on HN. And good links by the commenters too. I love Feynman's classic style of "explaining to a 5 year old" on Cold Welding. The reason for this unexpected behavior is that when the atoms in contact are all of the same kind, there is no way for the atoms to “know” that they are in different pieces of copper. When there are other atoms, in the oxides and grea…
Note that this is a big oversimplification- it doesn't apply to gage blocks. Cold welding and similar phenomenon can only truly happen with metallic bonds and very large grain sizes. Non-metallic bonds are structured and require precise orientations and conditions to reform. Metals are still structured -metals have crystal grains- and the microscale structure needs to line up in order to reform. In cold welding, you…