Superlubricity – tuning friction to the point where it disappears | Hacker News Reader

Superlubricity – tuning friction to the point where it disappears

newsoffice.mit.edu

33 pointsSami_Lehtinen15 comments

This seems to me to go a long way toward explaining why dissimilar metals make the best bearing interfaces, i.e. the atomic lattices don't match up.

I would be surprised if this phenomenon caused the friction between metallic surfaces. The surface of metals aren't that flat on nanoscale (even if they are well polished).

This also kind of seems analogous to the electron Cooper pairs moving through a superconductor... As one electron moves down into a trout, the other moves up into a peak, and because of the push/pull balancing interaction of their paired up connection, energy is not dissipated (as heat), and in-turn no additional energy is required for propagation... They just keep on moving.

I haven't heard this theory of superconductivity before. Is it new?

It isn't new. That would be BCS Theory[1].

[1]: http://en.wikipedia.org/wiki/BCS_theory

It's pretty funny, when we can finally build a machine in perpetual motion, nobody cares anymore.

This is only perpetual motion in the same sense as a rock in space. We've known about Newton's First Law for a while before this.

Even if there is zero surface-surface friction, there is still friction and resistance generated by, eg, the flexing of the materials making contact.

Good point, this will bar more complicated mechanisms. But a ring spinning forever around a dimple (in vaccuum of course) should work. Constant pressure so no flexing.

"Perfect vacuum" is a classical physics concept which abstracts away quantum effects. In short, it isn't real, and it can never exist.

https://en.wikipedia.org/wiki/QED_vacuum

So, your perpetual motion device will inevitably interact with virtual particles with momentum contrary to its own, and therefore run down.

Even if you have problems with that, consider this: It's impossible to cool anything to 0K (absolute zero); all warm bodies (warmer than absolute zero) give off photons; therefore, your moving parts will interact with photons carrying momentum contrary to their own, and therefore be slowed and eventually halted. Again, this is unavoidable.

So the simple classical picture of a rock in simple inertial motion through the vacuum of space is valid as a simplification. Remember, though, that it's equally valid to construct a coordinate system where the rock is stationary and everything else is in perpetual motion.

Friction is not the (only) obstacle to perpetual motion. The main problem is conservation of energy.

Please explain that for me, because resistance is the thing that burns the kinetic energy off to other forms (such as heat). If you remove resistance, what is the problem?

Sure, if you remove all resistance it won't stop, that's Newton's First Law. But usually "perpetual motion" means you'd be able to harness the motion somehow, which is still not the case.

>A perpetual motion machine of the third kind, usually (but not always)[12] defined as one that completely eliminates friction and other dissipative forces, to maintain motion forever (due to its mass inertia).

http://en.wikipedia.org/wiki/Perpetual_motion#Classification

This was the type I refered to.

You know how if you drop a conductive material between two magnets, it slows down?

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