Modern Physics vs Classical Physics

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Discussion Overview

The discussion explores the distinctions between modern physics and classical physics, focusing on definitions, applications, and the evolution of concepts within the field. Participants examine the implications of these differences and how they relate to the understanding of forces and dynamics.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that modern physics provides a more accurate definition of force compared to classical physics, which primarily defines acceleration in terms of force and mass.
  • One participant posits that modern physics focuses on the dynamics of space, while classical physics deals with dynamics within space.
  • Another viewpoint contrasts classical physics, which addresses larger, slower phenomena, with modern physics, which is necessary for understanding smaller, faster entities like electrons.
  • A participant mentions varying definitions of classical versus modern physics, noting that some define classical physics as everything before 1905, while others include theories that do not utilize quantum mechanics as classical.
  • It is proposed that in quantum mechanics, the concept of force is less relevant, with potentials playing a more significant role, and that quantum field theory moves away from potentials entirely.
  • One participant introduces the experimental history of light as a case that complicates simple distinctions between classical and modern physics.
  • Classical physics is described as being based on Newtonian principles, while modern physics incorporates general relativity and quantum mechanics.

Areas of Agreement / Disagreement

Participants express a range of definitions and interpretations regarding the separation between classical and modern physics, indicating that multiple competing views remain without a consensus on a singular definition or understanding.

Contextual Notes

There are limitations in the definitions provided, as they depend on specific interpretations of historical and theoretical developments in physics. The discussion does not resolve the complexities surrounding the definitions of force in different contexts.

Senjai
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Just curious, what's the difference?

I was told be someone that modern physics has ways of accurately defining what a force is, while classical physics does not define forces, only acceleration in terms of force and mass.

Again, just curious.. What are the major differences? Is one wrong? (similar to how high school students were taught the bohr model earlier to discover it was wrong later.)

Senjai
 
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Correct me if I wrong in my summation. Modern physics deals mostly with the dynamics of the space, classical - dynamics in the space.
 
one simple difference is that classical physics deals with slow, big things (from bullets to planets) while modern physics was required for smaller, faster moving things (like electrons).

GR is a counter example, of course.
 
There are a few varying definitions of what separates classical physics from modern physics. Some day that everything pre-1905 is classical, and everything afterwards is modern. The defnition I prefer, and have heard most often, is that every branch of physics that does not utilize a quantum treatment is classical, and any physics that is based on quantum mechanics is modern. So classical physics includes mechanics, E&M, the kinetic theory of gases, optics (including the whole wave/particle duality thing), and special and general relativity (yes, I've heard a cosmologist call GR a classical theory). Modern physics then includes non-relativistic quantum mechanics, quantum statistical mechanics, nuclear/particle stuff, and field theory.

Regarding forces, I think you might have heard slightly incorrectly. In quantum mechanics we actually don't talk about forces at all. In non-relativistic quantum mechanics, potentials (potential energy and the magnetic vector potential) play a more direct role than in classical physics. And in relativistic quantum mechanics, or quantum field theory, we get rid of potentials altogether and talk about fields. It's actually somewhat difficult to do a quantum mechanics calculation while talking about "forces," without fudging the formalism somewhat.
 
The experimental history of light is another interesting case that betrays my simple assertion above.

And non-linear (chaos) dynamics perhaps too.
 
Classical physics is based on Newtonian physics where as modern physics supplements upon that with general relativity and quantum mechanics
 

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