Physics simulators
Fields and the equations that move energy through space.
Electromagnetic Waves
Shake a charge and watch its field ripple outward as a glowing shell, at the speed the medium allows. Build a dipole antenna to see its radiation glow as a doughnut round the wire, with E and B turning transverse in 3D, or switch to statics for Coulomb field lines and the magnetic circles round a wire.
Wi-Fi in a House
Maxwell's equations on the GPU over a whole house at the true Wi-Fi wavelength: watch 2.4 and 5 GHz spill through doorways, leave dead spots a few centimetres across and fade behind brick and concrete, with the signal a phone would read in every room.
Entropy
Lift the wall and a gas fills its box. Flip every velocity and it flows home; nudge one particle by a billionth and it never does. Entropy counts arrangements, and chaos makes the count win.
Heat Equation
Watch heat diffuse through a 3D room as glowing fog, from a radiator to a cold window, paint in your own heat or cold, and see a thermometer settle into steady state.
Wave Equation
A drum skin where every point accelerates toward the average of its four neighbours. Put a probe anywhere and watch that pull live: down on a crest, up in a trough, nothing on a straight slope. Swap in the heat equation and the same pull only slides the point into place.
Normal Modes
Every object has a few shapes it can hold while it vibrates, each ringing at its own note. Pluck it and the motion splits into those notes: whole multiples on a string, an untuned jumble on a drum.
Phonons
Every mass obeys Hooke’s law and pulls only on its neighbours. Out comes a pulse travelling at a speed nobody wrote down, and a shortest possible wavelength.
Wave Interference
Two sources of ripples cross and combine into bright and dark fringes. Drag the sources to see the pattern behind the double-slit experiment.
Ideal Gas
A few hundred atoms in a glass cylinder under a piston. Pressure is the drumming of their impacts, temperature is how fast they fly, and PV = NkT is what that adds up to: squeeze, heat or insulate and watch it hold.
Stationary Action
Bend the path a particle takes between two fixed events and watch its action get worse. Rolling that downhill turns out to be Newton in disguise.
Band Theory
Bring a line of atoms together and every level splits into a band. Which bands are full, and how wide the gap is, decides metal, semiconductor or rock.
Quantum Tunnelling
Fire a wave packet at a wall taller than its energy. Classically it bounces straight back; as a wave, part of it leaks through the wall and out the far side.
Wavefunction Collapse
A matter wave spreads through space as a cloud of probability until a measurement finds it at one single point. Fire particles at a screen one by one and the interference fringes build up dot by dot.
Atomic Orbitals
The exact hydrogen orbitals drawn as glowing clouds of probability: shells and nodal planes, the phase winding of m, the signed lobes of chemistry, measurements that collapse the cloud to a point, and superpositions that slosh and emit light.
Stern-Gerlach Experiment
A beam of atoms should smear into a band and arrives as two spots. Chain the analysers, turn the next one, and measuring x wipes out what was known about z.
Quantum Gates
Build a circuit on two qubits and watch the amplitudes, their phases and both Bloch arrows move together. Then build the one circuit whose arrows shrink to nothing.
Nuclear Fission
One neutron splits one nucleus and two more fly out. Turn the enrichment, the size and the control rods and watch the chain die, hold steady, or run away.
Nuclear Fusion
Slam light nuclei together hard enough to tunnel through their own repulsion, and chase the one line every star has to cross: power out beating power lost.
Special Relativity
Space and time are one fabric. Boost to a moving frame and its grid skews: clocks tick slow, rulers shrink, and simultaneity comes apart. Yet every arrow in spacetime keeps one length that all observers agree on.
General Relativity
Hang two clocks above a black hole, a neutron star or the Earth: the low one runs slow, so its light flashes arrive stretched, and a clock carried down comes back younger. Then lay a ruler between two circles and it needs more rungs than their circumferences allow: space is curved too, not just time.
Black Hole
See a black hole the way its light does: every pixel is a photon traced through curved spacetime, so the disk wraps over the top and the sky folds round a shadow 2.6 times the horizon. Then put a particle in orbit and watch it trace rosettes, plunge inside 3 rₛ, and its clock run slow.