Category: Physics

The motion of one of the simplest dynamical systems, a torqued, damped, nonlinear pendulum, can be infinitely complicated. Consider a simple pendulum of length and mass rigidly connected to an axle of radius wrapped by a rope that hangs down one side with a mass climbing up and down it, as in the attached animation.…

Quantum field theory predicts that the temperature of empty space should depend on the observer’s motion, increasing proportionally with acceleration. Here I attempt an accessible introduction to this striking effect, related to Hawking radiation and discovered independently by Fulling, Davies, and Unruh, assuming only sophomore-level physics (including hyperbolic functions) with some assistance from Mathematica. Hyperbolic…

The forces between two electric charges in arbitrary motion are complicated by velocity, acceleration, and time-delay effects. The forces need not even lie along the line joining the two charges! Suppose a source charge is at position with velocity and acceleration , and a test charge is at position with velocity and acceleration . Let…

Overcoming decades of enormous physics and engineering challenges, and despite persistent pessimism, skepticism, and criticism, the National Ignition Facility has achieved an historic milestone for controlled nuclear fusion, a target energy gain factor of . Last week, NIF focussed the world’s most powerful laser pulse on a small gold cylinder that converted the incident ultraviolet light into x-rays and caused an enclosed…