Newtonian mechanics and relativistic mechanics (or specifically, classical mechanics and relativistic mechanics) are two frameworks used to describe the motion of objects. Here are some key differences between the two:
Scope of applicability: Newtonian mechanics is applicable to objects moving at speeds much slower than the speed of light and in gravitational fields that are not extremely strong. Relativistic mechanics, on the other hand, is necessary when dealing with objects moving at significant fractions of the speed of light or in the presence of strong gravitational fields.
Time and space: In Newtonian mechanics, time and space are considered absolute and separate entities. In contrast, in relativistic mechanics, time and space are combined into a four-dimensional framework known as spacetime, and their relationship can be influenced by the motion and gravitational fields of objects.
Speed of light: Newtonian mechanics assumes that the speed of light is infinite and has no fundamental limit. Relativistic mechanics, however, incorporates the finite and constant speed of light as a fundamental principle. This leads to various effects, such as time dilation and length contraction, which are not accounted for in Newtonian mechanics.
Energy and momentum: In relativistic mechanics, energy and momentum have different forms and relationships compared to Newtonian mechanics. The famous equation E=mc² relates energy (E) and mass (m), indicating that mass can be converted into energy and vice versa. Additionally, the momentum of an object is modified by the factor γ (gamma), which depends on the object's velocity and approaches infinity as the velocity approaches the speed of light.
Regarding which framework physicists consider more accurate, it depends on the context. Newtonian mechanics provides an excellent approximation for most everyday situations and remains highly useful in many fields of science and engineering. However, when dealing with phenomena involving high speeds, strong gravitational fields, or subatomic particles, relativistic mechanics is essential for accurate predictions.
Physicists generally consider relativistic mechanics to be more accurate because it encompasses a broader range of phenomena and has been extensively verified by experimental evidence. Relativistic mechanics has successfully explained and predicted various phenomena that cannot be accounted for within the framework of Newtonian mechanics. However, it is worth noting that Newtonian mechanics is still widely used due to its simplicity, convenience, and its accurate predictions in many situations that do not involve extreme conditions.