Seven laws.
Five constants.
One loop.

An interactive field guide to how physics connects — from Newton's falling apple to the glowing edge of a black hole. Every demo below shares the same handful of fundamental constants, and by the end they all collide in a single equation Stephen Hawking wrote on a blackboard in 1974.

Begin the loop ↓
TAP A STATION · THE LOOP CLOSES WHERE IT BEGAN
THE RECURRING CAST

Watch these six. Each glows when it enters a section — all six ignite at once inside the black hole.

STATION 1 / 7 · THE PULL

Gravity — every mass whispers to every other

Newton's 1687 law says the attraction between two bodies grows with their masses and collapses with the square of their distance. The constant G sets how loud the whisper is — and it is astonishingly quiet.

ORBIT SPEED FOLLOWS ω = √(GM/r³) · ARROWS SHOW MUTUAL FORCE
F = G M mr2
Force F
Orbital period
Same force, in everyday terms
STATION 2 / 7 · THE EXCHANGE RATE

E = mc² — mass is frozen energy

Einstein's 1905 result is a currency conversion: multiply any mass by the speed of light squared and you get the energy it stores. The exchange rate c² is so extreme that a paperclip holds a small city's yearly power.

PHOTON FLUX SCALES WITH log E · TOTAL CONVERSION SHOWN (ANTIMATTER-STYLE)
E = mc2
Energy released
In tons of TNT
Hiroshima bombs
US homes powered · 1 yr

The Sun runs on this ledger: fusing hydrogen shaves ~0.7% off the mass and radiates the difference. So does a black hole's accretion disk, the most efficient furnace known.

STATION 3 / 7 · THE CURL

Magnetism — moving charge bends space around it

Run a current through a wire and rings of magnetic field wrap around it — curl your right hand to see which way. The strength is set by μ₀, the vacuum's magnetic stiffness.

⊙ CURRENT OUT OF SCREEN · FIELD RING SPEED ∝ B(r) · PROBE = ORANGE DOT
B = μ₀ Ir
Field at probe B
vs Earth's field (~50 µT)
Compass verdict
STATION 4 / 7 · THE CHARGE

Electricity — gravity's law, wearing a plus and a minus

Coulomb's force is Newton's 1/r² pull reborn for charge — except it can also push. Its strength hides ε₀, the vacuum's electric give. Between two electrons, this force beats gravity by a factor of 1042.

FIELD LINES TRACED LIVE FROM E(x,y) · DRAG SLIDERS TO FLIP SIGNS
F = 1ε₀ q1q2r2
Force
Character
vs gravity between the same objects
The bridge Maxwell built (1865). Stations 3 and 4 secretly contain Station 2. Combine the vacuum's two personalities and out falls the speed of light:
c = 1 / √(ε₀ μ₀) = 299,792,458 m/s
Light is electricity and magnetism chasing each other through empty space.
INTERLUDE · STATION 4½ · THE PUMP

The battery — a charge pump with its price in volts

A battery is chemistry doing electrical work: each electron that crosses it gets lifted uphill by an energy of qV. Close the loop and a current flows — and here is the twist: the electrons themselves crawl, while the field that shoves them moves at essentially the speed of light. This one loop of wire quietly contains Stations 3, 4 and 6.

ELECTRON DRIFT SHOWN ×20,000 · BULB GLOW ∝ POWER · CONVENTIONAL CURRENT RUNS THE OTHER WAY
I = VR · vd = In A e
Current I
Power P = VI
Electron drift vd
Energy per electron
Field this wire makes 2 cm away — Station 3's law, live
The exhibit's common currency. Each electron crossing this battery banks qV9 eV of chemical energy — the electron-volt. The Bohr atom (Station 5) prices its rungs in the same unit, and Arrhenius (Station 6) sets its activation tolls in it. One coin, three stations.
STATION 5 / 7 · THE LADDER

Atoms — electricity caged by the quantum

Station 4's Coulomb force holds an electron near a proton — but Planck's constant ħ forbids it from orbiting just anywhere. Only rungs on a ladder are allowed. Jump down a rung and the atom pays the energy difference as one photon of exact color.

BOHR HYDROGEN · ORBIT RADIUS ∝ n² · EMITTED PHOTON COLORED BY ITS TRUE WAVELENGTH
En =mee48ε₀2h2n2 =13.6 eVn2
Energy Eₙ
Orbit radius
Photon if it drops one rung (n → n−1)

This ladder is why neon glows red-orange and why astronomers can read a star's recipe from 100 light-years away — every element's rungs are a fingerprint.

STATION 6 / 7 · THE CROWD

Chemistry — temperature is a speed distribution

Zoom out from one atom to 10²³ of them and a new constant takes the stage: Boltzmann's kB, the bridge between temperature and energy. Maxwell and Boltzmann showed a warm gas is a bell-curve of speeds — and chemistry happens in its fast tail.

LIVE GAS + MAXWELL–BOLTZMANN CURVE · PARTICLES COLORED BY SPEED · ▲ = MOST-PROBABLE SPEED
f(v) v2 emv²/2kBT
Most-probable speed
Avg energy · ³⁄₂k_BT
Fraction hot enough to react · e^(−Eₐ/k_BT)

That exponential is Arrhenius' law — the reason cooking is fast and rust is slow. Keep an eye on kB: it returns, impossibly, at the edge of a black hole.

STATION 7 / 7 · THE ARC

Newtonian physics — F = ma, and the loop closes

Every trajectory in this room obeys three lines Newton wrote in 1687. Launch a projectile and watch F = ma draw a parabola — then notice that the g you chose is nothing but Station 1 in disguise.

DASHED = PREDICTED PARABOLA · SOLID = INTEGRATED F = ma, LIVE
F = m a · g = GMplanetR2
g (from G·M/R²)
Range
Peak height
Flight time
⟲ The loop closes. Newton's little g = 9.81 m/s² is Station 1's law evaluated at Earth's surface — the exhibit has walked one full circle:
GRAVITY → ENERGY → MAGNETISM → ELECTRICITY → ATOMS → CHEMISTRY → MOTION → GRAVITY…
Now take everything on the ring — G, c, ε₀, μ₀, ħ, kB — to the one object that needs them all at once.
FINALE · WHERE THE LOOP COLLAPSES

The Black Hole Codex — one boundary, every constant

Pack enough mass inside its Schwarzschild radius and spacetime folds shut. The boundary — the event horizon — turns out to be a thermodynamic object with a temperature (Hawking, 1974), an entropy (Bekenstein, 1972), and, astonishingly, an electrical surface resistance straight out of Maxwell's equations.

STARFIELD LENSED · PHOTON RING AT 1.5 r_s · INFALL REDDENS & FREEZES AT HORIZON · RIM FLASHES = HAWKING PAIRS
rs = 2GMc2 · TH = ħc3GMkB
Schwarzschild radius r_s
Hawking temperature T_H
Entropy S / k_B
≈ information content
Evaporation time
Photon sphere · 1.5 r_s
Context
MAXWELL MEETS THE HORIZON · THE MEMBRANE PARADIGM

Apply Maxwell's equations at the horizon boundary (Znajek 1978; Damour; Thorne & Price's membrane paradigm, 1986) and the horizon behaves exactly like a conducting membrane with a fixed surface resistivity:

RH = √(μ₀/ε₀) 377 Ω per square

That number is the impedance of free space — the same constant hiding in Stations 3 & 4. It does not depend on the black hole's mass at all: slide M above and watch everything change except this. Electromagnetism stamps its signature on gravity's most extreme boundary — and via the Blandford–Znajek process, magnetic fields threading a spinning horizon power the brightest jets in the universe.

Derivation trail · the Schwarzschild radius in 4 steps
01
Ask when escape speed reaches light speed. Energy balance for a mass m leaving mass M:  ½mv² = GMm/r.
02
Set v = c (Station 2's constant) and cancel m:  ½c² = GM/r.
03
Solve: rs = 2GM/c². John Michell reasoned this way in 1783; remarkably, full general relativity (Schwarzschild 1915) lands on the same formula.
04
GR reinterprets it: not a speed limit but a one-way surface where time-like paths all point inward. Nothing special is felt crossing it — for a big hole, you wouldn't even notice.
Why kB? · the thermodynamic horizon
01
Bekenstein (1972): horizons must carry entropy or the second law of thermodynamics dies when you drop hot gas into a hole.
02
Hawking (1974): quantum fields near the horizon leak thermal radiation. Anything thermal needs Station 6's constant — so kB enters gravity.
03
Result: S = kBc³A/4Għ — entropy proportional to horizon area, counted in Planck-sized tiles. One formula, four constants, four fields of physics.
04
Read it as information: the hole's surface, not its volume, sets how many bits it can hide — the seed of the holographic principle.
FIELD DISPATCH · MEASURING CONSTANTS WITH SPACETIME ITSELF

Gravitational waves — the constants, re-measured by collisions

When two black holes merge, they broadcast a chirp in spacetime. Because general relativity predicts the waveform's loudness from first principles, each event is a standard siren — a self-calibrating distance marker that lets us re-measure cosmic constants with no ladder of assumptions.

TOP: INSPIRAL → MERGER → RINGDOWN · BOTTOM: STRAIN h(t), THE LIGO CHIRP
fend c363/2πGMtot · h 1/D
Final orbital tone
Strain at Earth (rel.)
Rule of the chirp
Heavier pair → deeper final note & shorter chirp · Farther → fainter, same shape. That shape-vs-loudness split is why sirens measure distance directly.
H₀ ≈ 70 km/s/Mpc
GW170817 + its light flash gave the first Hubble-constant reading fully independent of the cosmic distance ladder — a new referee for the "Hubble tension."
|Δv|/c ≲ 10⁻¹⁵
Gravity's waves and light from the same 2017 merger arrived ~1.7 s apart after 130 million years of travel: gravity moves at Station 2's c to exquisite precision.
390 events
The GWTC-5.0 catalog (May 2026) added 161 detections from run O4b, pushing population-level tests of general relativity to record precision.
2.7 % on H₀
Forecast: with run O5, "dark sirens" alone — no light needed, just Station 1's G and Station 2's c — should pin the Hubble constant to a few percent.
RESIDENT VOICE · STEPHEN HAWKING (1942–2018)

"Black holes ain't as black as they are painted."

The equation glowing in the Codex above — TH = ħc³/8πGMkB — is Hawking's. He spent his 2016 BBC Reith Lectures walking the public along the very boundary this exhibit explores.

EXIT THROUGH THE GIFT SHOP · SOUVENIR №1

The lodestone — magnetite, the universe's oldest fridge magnet

Magnetite (Fe₃O₄) is the naturally magnetized rock that gave us the compass — and its field is still rated in gauss, after the man whose law explains why every magnet you'll ever buy has two poles. Move the compass through the stone's field and watch it argue with the entire planet.

DIPOLE FIELD + EARTH'S UNIFORM FIELD · THE NEEDLE POINTS ALONG THE VECTOR SUM
B·dA = 0 · E·dA = qε₀
Stone's field at the compass
Needle swings off north by
Stone out-pulls Earth within
Who owns the needle right now
The two Gauss's laws are half of Maxwell. The dashed loop drawn around the stone is a Gaussian surface: every field line that exits it comes back in, so the net magnetic flux is exactly zero — nature stocks no magnetic monopoles. Draw the same surface around one battery terminal and the electric flux is not zero: charge exists, and ε₀ sets the exchange rate. Those two statements are Maxwell's equations №1 and №2 — the other two power the light-speed bridge back at Station 4.