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| Motion | |
|---|---|
| Name | Motion |
| Field | Physics, Mechanics |
| Introduced | Antiquity |
| Notable figures | Aristotle, Isaac Newton, Galileo Galilei, Albert Einstein, Leon Foucault |
Motion
Motion is the change in position of a body or system relative to a chosen set of reference points over time. It is central to Aristotelian physics and Newtonian mechanics and was reframed by Galileo Galilei and Isaac Newton before being further generalized by Albert Einstein in special relativity and general relativity. Motion underlies technologies from the steam engine to the Global Positioning System and informs fields as diverse as astronomy, robotics, aeronautics, and molecular biology.
Fundamental concepts include position, displacement, distance, speed, velocity, and acceleration as embodied in works by Euclid, Archimedes, Nicolaus Copernicus, and later formalized by Isaac Newton in the Philosophiæ Naturalis Principia Mathematica. Reference frames such as inertial and non-inertial frames appear in problems treated by Galileo Galilei and formalized in discussions by Ernst Mach and Henri Poincaré. Conservation principles—momentum, energy, and angular momentum—feature prominently in analyses by Emmy Noether and were used in the development of Lagrangian mechanics and Hamiltonian mechanics by Joseph-Louis Lagrange and William Rowan Hamilton.
Kinematics describes motion without regard to causation, tracing back to geometric treatments in Euclid and kinematic analyses by Galileo Galilei in his studies of uniformly accelerated motion. Trajectories, instantaneous velocity, and acceleration are formalized using calculus developed by Isaac Newton and Gottfried Wilhelm Leibniz. Parametric, polar, and Cartesian methods appear in work by René Descartes and Pierre-Simon Laplace, while modern treatments employ vector calculus and differential geometry as advanced by Carl Friedrich Gauss and Bernhard Riemann.
Dynamics links motion to causes through force, mass, and interaction laws. Isaac Newton's three laws of motion and law of universal gravitation set the foundation for classical dynamics, extended in continuum mechanics by Augustin-Louis Cauchy and Siméon Denis Poisson. Electromagnetic forces described in James Clerk Maxwell's equations influence charged-particle motion, while Ludwig Boltzmann and James Prescott Joule informed thermodynamic and statistical forces in many-body systems. Modern force descriptions include the strong and weak interactions characterized in work at laboratories such as CERN and in theories by Murray Gell-Mann and Steven Weinberg.
Common categories include translational, rotational, vibrational, oscillatory, and random motion. Planetary and satellite motion studied by Johannes Kepler and Edmond Halley exemplify orbital dynamics; rigid-body rotation treated by Euler and Simeon Poisson; wave motion analyzed by Christiaan Huygens and Thomas Young; and Brownian motion explained by Albert Einstein and experimentally confirmed by Jean Perrin. Complex behaviors such as chaotic motion are associated with studies by Henri Poincaré and Edward Lorenz.
Equations of motion arise from Newtonian F = ma, Lagrange's equations, and Hamilton's equations; variational principles such as the principle of least action were articulated by Pierre-Louis Moreau de Maupertuis and formalized by William Rowan Hamilton. Differential equations—ordinary and partial—appear in models from Leonhard Euler's fluid equations to the Navier–Stokes equations and the Schrödinger equation in quantum mechanics developed by Erwin Schrödinger. Perturbation methods, Fourier analysis by Joseph Fourier, and linear algebra foundations by Carl Friedrich Gauss and Augustin-Louis Cauchy support solution techniques. Conservation laws linked to symmetries are stated in Noether's theorem by Emmy Noether.
Reference frames define measurable motion; inertial frames underpin Newtonian mechanics while accelerating frames require fictitious forces as discussed by Ernst Mach and treated in rotating-frame analyses used in Foucault's pendulum experiments by Leon Foucault. Albert Einstein's special relativity redefined simultaneity and introduced Lorentz transformations developed from work by Hendrik Lorentz and Hermann Minkowski, altering kinematic relations at high velocities. General relativity by Albert Einstein interprets motion as geodesic propagation in curved spacetime produced by mass–energy, building on tensor calculus by Gregorio Ricci-Curbastro and Tullio Levi-Civita.
Understanding motion enabled the industrial revolution via machines exemplified by designs from James Watt and powered transport such as the steam locomotive and Wright brothers' aircraft. Navigation advances incorporated motion models in systems like the Global Positioning System and spacecraft trajectories planned by teams at NASA and Roscosmos. Robotics and control theory—drawing on work by Norbert Wiener and implemented in companies such as Boston Dynamics—use motion planning and dynamics. In medicine, motion analysis techniques from biomechanics informed by Hermann von Helmholtz support prosthetics and gait studies; in materials science, phonon and molecular motion affect thermal properties central to research at institutes like Max Planck Society.