The principle of least action.
Other related questions:
Q: What are the principles of the theory of relativity?
A: The theory of relativity is a theory that explains the physical laws that govern how objects move. It is based on the idea that the laws of physics are the same for all observers, regardless of their relative motion.
Q: What is non-relativistic theory?
A: In physics, non-relativistic theory is a theory that does not take into account the effects of special relativity. Non-relativistic theories are often used in situations where the speeds involved are much smaller than the speed of light.
Q: What is not relative in the special theory of relativity?
A: There is no definitive answer to this question since it depends on how you interpret “relative” in the context of special relativity. However, some concepts that are often considered to be absolute in special relativity include the speed of light, the spacetime interval, and the mass-energy equivalence.
Q: What are the two main principles of general relativity?
A: The two main principles of general relativity are the equivalence principle and the general principle of covariance.