classical physics

Physics that does not make use of quantum mechanics or the theory of relativity. Newtonian mechanics, thermodynamics, and Maxwell's theory of electromagnetism are all examples of classical physics. Many theories in classical physics break down when applied to extremely small objects such as atoms or to objects moving near the speed of light.Classical mechanics refers to the classical physics of bodies and forces, especially Newton's laws of motion and the principles of mechanics based on them. Compare quantum mechanics.



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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


What is classical physics?

Classical physics refers to physics not involving quantum mechanics or the theory of relativity.

Physics is the branch of science that deals with things like motion, energy, and force. Classical, in this context, means standard or accepted, as opposed to experimental.

The term is used to distinguish it from modern physics, which does involve quantum mechanics and relativity.

Classical physics meaning and branches

Sometimes, scientific breakthroughs mean that we throw out everything we thought we knew. When Albert Einstein came up with his theories of relativity and quantum mechanics, that almost happened to physics. The old theories couldn’t explain everything—but they could still explain a lot of things. Because they were still important and useful, but because they belonged to a completely different way of seeing the world, physics split into two main branches: classical physics and modern physics.

Classical physics involves classical mechanics (the study of the movement of fluids and particles), thermodynamics (the study of temperature and heat transfer), and electromagnetism (the study of electricity, magnets, and electromagnetic waves). Classical physics can be described as the study of the physical world that’s visible to the naked eye—in other words, the things that are macroscopic. It’s based on Isaac Newton’s laws of motion and gravity (because of this, classical physics is also called Newtonian physics) and it is the basis of various other branches of science like chemistry and biology.

In the late 1800s, however, scientists started to explore the things that classical physics couldn’t properly explain. This resulted in the theories of relativity and quantum mechanics, which required a whole new model of physics. But in the “normal world”—the visible, physical world—the old laws of physics continued to work perfectly well. Classical physics is what you might call “practical physics”—for most practical, everyday purposes, classical physics is still important and useful.

Modern physicists may be engaged in study that goes way beyond the practicality of classical physics, but that’s not to say that they no longer pay classical physics any attention. There are lots of questions in classical physics that still haven’t been answered, or that scientists are still arguing about.

Did you know ... ?

There are a lot of basic answers to the question “How do airplanes fly?” But even with all the knowledge of classical physics, the truth is that physicists still don’t know everything about how it works.

What are some real-life examples of classical physics?

Much of classical physics is based on the observations of Isaac Newton, who laid the groundwork for classical mechanics.


What other words are related to classical physics?

Quiz yourself!

Which of the following is NOT a branch of classical physics?

A. thermodynamics
B. electromagnetism
C. quantum mechanics