I Modern Atom Model: Is It Perpetual Motion?

  • I
  • Thread starter Thread starter dom_quixote
  • Start date Start date
  • Tags Tags
    Atom Model
dom_quixote
Messages
50
Reaction score
9
Is the current atomic model a kind of perpetual motion?
 
Physics news on Phys.org
dom_quixote said:
Is the current atomic model a kind of perpetual motion?
It is not a perpetual motion machine. “Perpetual motion” is not forbidden by the laws of physics, just “perpetual motion machines”.
 
  • Like
Likes aaroman, dom_quixote, russ_watters and 3 others
dom_quixote said:
Is the current atomic model a kind of perpetual motion?
In a QM atom there is no motion at all in the classical sense. The atom is described by a state (aka wave-function) and is governed by conservation laws, but there are no perpetual classical trajectories.
 
  • Like
Likes dom_quixote, russ_watters and vanhees71
The answer will depend upon your definition of Perpetual and Motion...
 
  • Like
Likes dom_quixote and russ_watters
dom_quixote said:
Is the current atomic model a kind of perpetual motion?
No. It only feels like that, because theoretical quantum mechanics is taught before theoretical statistical mechanics. So you first teach it in a way as if temperature would be exactly zero. But at zero temperature, all degrees of freedom are frozen out, hence all dissipative forces seem to be absent.

On the other hand, with respect to crystallization, molecules and chemical reactions, room temperature is often surprisingly close to zero. (But with respect to electrical and heat conduction, it is not close to zero.) There are some interesting considerations elaborating this near the end of E. Schrödinger's What is life?
NERNST'S THEOREM
When does a physical system - any kind of association of atoms - display 'dynamical law' (in Planck's meaning) or 'clock-work features'? Quantum theory has a very short answer to this question, viz. at the absolute zero of temperature. As zero temperature is approached the molecular disorder ceases to have any bearing on physical events. This fact was, by the way, not discovered by theory, but by carefully investigating chemical reactions over a wide range of temperatures and extrapolating the results to zero temperature - which cannot actually be reached. This is Walther Nernst's famous 'Heat Theorem', which is sometimes, and not unduly, given the proud name of the 'Third Law of Thermodynamics' (the first being the energy principle, the second the entropy principle).
Quantum theory provides the rational foundation of Nernst's empirical law, and also enables us to estimate how closely a system must approach to the absolute zero in order to display an approximately 'dynamical' behaviour. What temperature is in any particular case already practically equivalent to zero?
Now you must not believe that this always has to be a very low temperature. Indeed, Nernst's discovery was induced by the fact that even at room temperature entropy plays an astonishingly insignificant role in many chemical reactions. (Let me recall that entropy is a direct measure of molecular disorder, viz. its logarithm.)

THE PENDULUM CLOCK IS VIRTUALLY AT ZERO TEMPERATURE
What about a pendulum clock? For a pendulum clock room temperature is practically equivalent to zero. That is the reason why it works 'dynamically'. It will continue to work as it does if you cool it (provided that you have removed all traces of oil!). But it does not continue to work if you heat it above room temperature, for it will eventually melt.

THE RELATION BETWEEN CLOCKWORK AND ORGANISM
That seems very trivial but it does, I think, hit the cardinal point. Clockworks are capable of functioning 'dynamically', because they are built of solids, which are kept in shape by London-Heitler forces, strong enough to elude the disorderly tendency of heat motion at ordinary temperature.
 
  • Like
Likes dom_quixote, protonsarecool and vanhees71
dom_quixote said:
Is the current atomic model a kind of perpetual motion?
It would have been, if it were a model of classical particles in motion.
 
  • Like
Likes dom_quixote and gentzen
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated... Source: https://www.physicsforums.com/insights/quantum-entanglement-is-a-kinematic-fact-not-a-dynamical-effect/ by @RUTA
If we release an electron around a positively charged sphere, the initial state of electron is a linear combination of Hydrogen-like states. According to quantum mechanics, evolution of time would not change this initial state because the potential is time independent. However, classically we expect the electron to collide with the sphere. So, it seems that the quantum and classics predict different behaviours!

Similar threads

Replies
3
Views
1K
Replies
11
Views
2K
Replies
8
Views
2K
Replies
1
Views
723
Replies
6
Views
1K
Replies
7
Views
442
Replies
10
Views
1K
Back
Top