Classical physics
Classical physics is the name given to physics as it developed from the Renaissance to the end of the 19th century.[1] Discoveries made from the beginning of the 20th century changed it into what is called modern physics.[2]
When classical physics works
Classical physics is not an exact description of the universe, but it is a very good approximation in ordinary conditions. These include matter moving at less than about 1 per cent of the speed of light, and only weak gravity, such as that of the Earth.[3][4] Very small objects, such as atoms and molecules, cannot be properly explained by classical physics.[5] Because people live in these conditions, classical physics seems natural and sensible, while many parts of modern physics seem strange.[6]
Classical and modern physics
Modern physics is made up of two revolutionary theories: relativity and quantum mechanics. Relativity deals with things that move very fast, and quantum mechanics with things that are very small.[7] Albert Einstein developed the theory of relativity in 1905.[8] Niels Bohr made fundamental contributions to quantum mechanics.[9]
Even so, classical physics is still widely taught. One reason is that knowledge of classical physics is needed to understand modern physics. Another is that it still gives an accurate description of the universe in a wide range of everyday situations.[10]
References
- ↑ "1.1 Physics: An Introduction". College Physics 2e. OpenStax. Retrieved 20 October 2026.
Physics as it developed from the Renaissance to the end of the 19th century is called classical physics .
- ↑ "1.1 Physics: An Introduction". College Physics 2e. OpenStax. Retrieved 20 October 2026.
It was transformed into modern physics by revolutionary discoveries made starting at the beginning of the 20th century.
- ↑ "1.1 Physics: Definitions and Applications". Physics. OpenStax. Retrieved 20 October 2026.
Classical physics is not an exact description of the universe, but it is an excellent approximation under the following conditions: (1) matter must be moving at speeds less than about 1 percent of the speed of light
- ↑ "1.1 Physics: Definitions and Applications". Physics. OpenStax. Retrieved 20 October 2026.
(3) only weak gravity, such as that generated by Earth, can be involved.
- ↑ "1.1 Physics: Definitions and Applications". Physics. OpenStax. Retrieved 20 October 2026.
Very small objects, such as atoms and molecules, cannot be adequately explained by classical physics.
- ↑ "1.1 Physics: An Introduction". College Physics 2e. OpenStax. Retrieved 20 October 2026.
Because humans live under such circumstances, classical physics seems intuitively reasonable, while many aspects of modern physics seem bizarre.
- ↑ "1.1 Physics: Definitions and Applications". Physics. OpenStax. Retrieved 20 October 2026.
Modern physics includes two revolutionary theories: relativity and quantum mechanics. These theories deal with the very fast and the very small, respectively.
- ↑ "1.1 Physics: Definitions and Applications". Physics. OpenStax. Retrieved 20 October 2026.
The theory of relativity was developed by Albert Einstein in 1905.
- ↑ "1.1 Physics: An Introduction". College Physics 2e. OpenStax. Retrieved 20 October 2026.
Niels Bohr (1885–1962) made fundamental contributions to the development of quantum mechanics, one part of modern physics.
- ↑ "1.1 Physics: Definitions and Applications". Physics. OpenStax. Retrieved 20 October 2026.
The first is that knowledge of classical physics is necessary to understand modern physics. The second reason is that classical physics still gives an accurate description of the universe under a wide range of everyday circumstances.