If you took two random objects and pressed them together, they would look a lot like taking two chunks of mountainous land and pressing them together. There’s almost no contact area between them; they only touch at a couple of the mountaintops and nowhere else.
This is what ‘flat’ surfaces look like on the microscopic level. If we carefully flatten and polish a material, it *will* actually stick, but even our best polishing techniques are far from perfect.
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