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Kenneth Krane's Modern physics begins a text on quantum and relativity theories with a few pages on the deficiencies of classical physics. [ 84 ] : 3 E.T. Whittaker's two volume A History of the Theories of Aether and Electricity subtitles volume one to The Classical Theories and volume two The Modern Theories (1900–1926).
Cartesian x-axis basis unit vector unitless current density: ampere per square meter (A/m 2) impulse: kilogram meter per second (kg⋅m/s) jerk: meter per second cubed (m/s 3) imaginary unit (electrical) unitless ȷ ^
This timeline lists significant discoveries in physics and the laws of nature, including experimental discoveries, theoretical proposals that were confirmed experimentally, and theories that have significantly influenced current thinking in modern physics. Such discoveries are often a multi-step, multi-person process.
There are two main descriptions of motion: dynamics and kinematics.Dynamics is general, since the momenta, forces and energy of the particles are taken into account. In this instance, sometimes the term dynamics refers to the differential equations that the system satisfies (e.g., Newton's second law or Euler–Lagrange equations), and sometimes to the solutions to those equations.
In physics, Hamiltonian mechanics is a reformulation of Lagrangian mechanics that emerged in 1833. Introduced by Sir William Rowan Hamilton , [ 1 ] Hamiltonian mechanics replaces (generalized) velocities q ˙ i {\displaystyle {\dot {q}}^{i}} used in Lagrangian mechanics with (generalized) momenta .
Predicate logic, originally called predicate calculus, expands on propositional logic by the introduction of variables, usually denoted by x, y, z, or other lowercase letters, and by sentences containing variables, called predicates. These are usually denoted by an uppercase letter followed by a list of variables, such as P(x) or Q(y,z).
5th century BC: The Greeks start experimenting with straightedge-and-compass constructions. [30] 5th century BC: The earliest documented mention of a spherical Earth comes from the Greeks in the 5th century BC. [31] It is known that the Indians modeled the Earth as spherical by 300 BC [32] 460 BC: Empedocles describes thermal expansion. [33]
Variational principles are found among earlier ideas in surveying and optics.The rope stretchers of ancient Egypt stretched corded ropes between two points to measure the path which minimized the distance of separation, and Claudius Ptolemy, in his Geographia (Bk 1, Ch 2), emphasized that one must correct for "deviations from a straight course"; in ancient Greece Euclid states in his ...