what is classical physics?and what are the theories of modern physics which have proven it wrong?
"Classical Physics" is, basically, any physics from before "Quantum Physics" and "Relativity" both developed around 1900. I would not say that classical physics was "proven wrong", just developed further.
In my opinion, classical physics deals with phenomena we can experience and manipulate directly, with a minimum of apparatus. There are new developments in classical physics all the time.
In some cases, "modern" physics (now almost 100 years old) provides a stronger foundation for classical phenomena: the color of copper, for example. In other cases, modern physics explores physical phenomena outside of our daily experience- the very fast, cold, small, or large.
So now that you've been given a couple examples of the extensions to Classical Physics (especially to extend to the very small with Quantum Mechanics, and the very large with Relativity), what do you think might be some things that Classical Physics has trouble handling accurately? You can look up Quantum Mechanics and Relativity at wikipedia.org for quick summaries to help your thinking....
Thinking about orbital mechanics might help...
If you know Maxwell's equations, then try to calculate this simple classical problem:
Two small balls are charged with a charge e. They have a mass m and are a distance of r apart. What acceleration do they experience?
If you calculate this in a coordinate system where they move (Coulomb+magnetic force) you will get a different result than in a system where they stand still (only Coulomb force).
This result contradicts Galileo's transformation (which should be replaced by relativistic Lorentz transformation to achieve consistency).
I think Classical Physics could be defined as an approximation of what Quantum Physics and Relativity discovered...I mean...The laws of classical physics doesn't change so much for our "order of magnitude", as a matter of fact they almost coincide with the "new physics" law...... but when we handle with subatomic distances and speeds close to the speed of light....The laws of Classical Physics are no more valid.
It's not so much that modern theories contradict classical theories, it's that observations gathered over time are not always consistent with the theories that have been developed over time.
Classical physics is *not* an approximation to quantum physics, except in the limiting case of weakly interacting point particles. Classical mechanics encompasses much more that that, which unfortunately is not the impression given by introductory physics textbooks.
Classical physics is the most generally applicable, most widely verified theory of physics, without question. Classical mechanics nicely describes my drive into work today; what does quantum mechanics have to say about it?
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