Is Perpetual Motion Possible at the Quantum Level? | Hacker News Reader

Is Perpetual Motion Possible at the Quantum Level?

quantamagazine.org

31 pointsdigital5546 comments

As long as people understand this means perpetual motion which is incapable of doing work is possible, because there's no indication that you can somehow extract anything from this.

It does make me wonder whether this could help with reversible computing, which reverses out everything except its output, which is all you pay energy for. In theory that would be vastly more efficient.

It could be fashioned into a neat desk toy though!

If such a toy could be created that displayed a perpetual quantum process, wouldn’t that count as doing work?

If so, then you could only have one that contains an unobservable perpetual quantum process; well, you’d need to trust that the seller that it does!

No, it wouldn’t count: “work” in this context is a technical physics term meaning a force applied over a distance.

If you are not observing some force over some distance then what, exactly, are you observing?

Constant motion doesn't require constant force.

observation requires the transmission of information to the observer, how is it being proposed to do this without force? The question on the table is "constructing a toy which demonstrates" and demonstration requires observation, I think is what is being said

For example, perfectly circular motion against no resistance requires no work since the force is always perpendicular to the motion.

he's saying you can't observe the phenomenon you are talking about without some additional work being done, which you might say is not part of the system, but it is part of the system that G*P proposed

I suspect it should be possible to have something that reflects light without doing work, or at worst absorbs a small portion of the incoming light and reflects the rest. Since it will sit on a desk, it will always be under light when observed by humans.

Brownian motion is perpetual, easily observable by microscope and still it's not doing any work.

To my very lay understanding, many quantum phenomena effectively "borrow" energy and then "repay" it. I wonder if one day we might find a way to delay that repayment long enough to accomplish things we otherwise couldn't.

If you are late on your energy loan payments, we will freeze your entire house to 5 Kelvin!

When life freezes your house, make a huge profit from using temperature difference against environment!

> So a time crystal is a phase of matter that spontaneously breaks this translation symmetry in time, to show you some kind of periodic, pulsing forever.

Isn't this Maxwell's Demon?

Only if it can choose arbitrary particles to let through a gate or reject.

Pulsing is just standing still, but with a bit extra flair.

Is that like falling with style?

Yes but in all directions at one!

No, but debates around Maxwell's Demon, Landauer's Principle and reversible computing are still kind of ongoing...

https://news.ycombinator.com/item?id=26908886

https://en.wikipedia.org/wiki/Landauer%27s_principle#Challen...

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

> Due to the unitarity of quantum mechanics, quantum circuits are reversible, as long as they do not "collapse" the quantum states they operate on.

Everything in this universe is in perpetual motion. Perpetual motion is trivial. Now, perpetual motion energy... now we have something to which the answer is and will always be "no".

Remember how superconductivity is about the complete (?) removal of friction thanks to quantum behaviour ?

Also this talk of quantum toys convinces me even more that the right framing is instead how our (subjective) information about a system can only decrease with time (or stay unchanging for exceptional systems such as these).

I was surprised superconductivity wasn't mentioned.

The new part here isn't the "perpetual motion" it's the complexity of the pattern.

I guess in some highly abstract sense it's like exciting a more complex resonance mode in a bounded system. The simplest mode gives you a simple output, more complex modes give you more complex outputs.

Superconductivity can be achieved at room temperature using pulses of electricity and vibration.

Isn’t perpetual motion the basis of the whole universe?

I mean, it hasn’t stopped yet, right? And it technically does all the work we do?

Doesn't the heat death of the universe contradict this?

Hasn't been empirically observed yet ;-P

Seriously thou: it seems reasonable to assume that our current models of the universe may be incomplete.

That's only one plausible ending to the universe, while perhaps favored, certainly far from being determined.

Then there's handwaving about given a large enough time scale energy should randomly concentrate enough to 'restart' the universe or something silly along those lines.

For myself I like the notion of the universe starting from a breaking of symmetry of whatever base form of energy the universe is built out of.

This allows for scattering of information, increasing diversity and complexity of the system, while also not adding or creating any new energy.

So if the universe can start in a place of equilibrium I'd imagine after heat death leads to a static state then 'restarting' is possible since it's happened at least once.

Perpetual motion actually means a violation of the first or second law of thermodynamics, rather than just something moving for a very long time.

That's perpetual motion machines, not perpetual motion. As a closed system, the universe (as a whole, not in parts) absolutely qualifies as being in perpetual motion, you just can't take energy out of the system.

(which is convenient for us, because we're part of the system)

what if some higher beings outside of our universe is using us (this universe) as a perpetual machine!

That’s a Rick and Morty episode

Then it's no longer perpetual, because the total energy in the system decreases over time.

Okay sure, it’s just that no one uses the term “perpetual motion” except to refer to perpetual motion machines as I described. Even the Wikipedia article on the topic is titled “perpetual motion.” And the entire universe, as far as we know, is not in perpetual motion. i.e. does not violate the laws of thermodynamics.

I don't think you can apply the laws of thermodynamics to the Big Bang.

First there was nothing, then there was everything. For currently undefined values of "first" and "then."

It's very much an out-of-scope problem.

No (serious) person uses it for the quantum scale either. Same problem, just other end of the scale. The very idea of "motion" doesn't even apply to quantum particles.

What does thermoquantum-mechanics even mean?

Mechanics of heat energy in a quantized system

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

perpetual motion is kind of guaranteed by quantum mechanics because absolute stillness is impossible.

What is the deal with physicists and clickbait? They've redefined "free will", "teleportation", and now "perpetual motion".

Lol, you think this it's the physicist choosing the headline? I mean, there are some dumbass physicists out there that will do anything for attention (max tegmark, Neil Tyson, etc.), but come on.

How did they redefine free will?

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

That doesn't seem to be redefining anything.

It goes to the beginnings of Western science.

The alchemist Cornelis Drebbel successfully harnessed what he considered to be the perpetual motion of the universe for his perpetual motion machine...

https://antonhowes.substack.com/p/age-of-invention-why-wasnt...

... that now we know to have been changes in temperature and atmospheric pressure, both concepts which were very fuzzy at the time, especially the pressure.

Sadly, his machine had made such an impression, that the legend of it then continued to plague patent applications for centuries !

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