A fast-moving rod is measured shorter along its motion — space itself foreshortened. The law is runnable: L = L₀/γ, and only along the direction of travel; transverse lengths are untouched. Down the center the terms go in, the engine contracts the rod, the proven length comes out. The blue team builds and defends it; the red team tries to break it.
source G. F. FitzGerald, The Ether and the Earth's Atmosphere, Science 13 (1889) 390; H. A. Lorentz (1892); A. Einstein, Zur Elektrodynamik bewegter Körper, Ann. Phys. 17 (1905) — wikisource · FitzGerald 1889. Rendered, not quoted. AMBER · pre-DOI primary sources
Contraction is not a force; it falls out of one number, the Lorentz factor:
β = v/c the speed as a fraction of light. γ = 1/√(1−β²) ≥ 1, growing without bound as β→1. L = L₀/γ the length measured along the motion. L⊥ = L₀ — perpendicular lengths are unchanged.
For the current speed, live from the four functions:
| quantity | value |
|---|
Moving rods shrink: FitzGerald (1889) guessed it to save the ether; Lorentz (1892) gave the transform; Einstein (1905) kept the formula and threw the ether away.
L = L₀/γ is the space component of the-lorentz-transformation — and it is exactly reciprocal to its time half, the-time-dilation (dt = γ·dτ). Length shrinks by 1/γ while time swells by γ, and the product is one. Each sphere is the next one's premise.
The blue team's live check: re-run the contraction on a known rod and confirm it is shorter (L=0.800·L₀ at β=0.6). If red flips the sign, this badge is where it shows.
Feed the engine two things: a rest length L₀ (the rod measured in its own frame, here normalised to 1.000) and a speed β = v/c in the interval 0 ≤ β < 1. Nothing may reach or pass c.
| input | meaning | range |
|---|---|---|
| L₀ | rest length (own frame) | 1.000 (fixed) |
| β = v/c | speed / speed of light | [0, 1) |
| along | length ∥ motion | contracts |
| across | length ⟂ motion | invariant |
Slide β below and the panel computes γ and the contracted length on the spot — never looked up.
Move β — γ and L = L₀/γ are computed from the four rules on the spot, and only the ∥ dimension shrinks.
What the machine proves: a rod in motion is shorter along its travel and unchanged across it. At β=0.6 → γ=1.25 → L=0.800·L₀; at β=0.8 → γ=1.667 → L=0.600·L₀; at β=0.99 → L≈0.141·L₀. At β=0 there is no contraction, and L·(dt/dτ)=1 with the-time-dilation — reciprocal, exactly.
The blue team's witness (left) confirms this live; the red team (right) tries to make the rod stretch.
And it is not what a camera sees. Terrell (1959) & Penrose showed that light-travel-time makes a fast object appear rotated, not simply foreshortened — the contraction is what you measure, not naively what you photograph. "Shorter" is a measurement, not a squeeze.
"The moving rod's atoms are physically compressed." Cut. In the rod's own frame nothing is stressed; the shorter number is a between-frames comparison born of the relativity of simultaneity — and it is symmetric.
"You could photograph the contraction directly." Cut. A snapshot shows Terrell–Penrose rotation; contraction is the measured length between simultaneous endpoints, not the raw image.
"Contraction has a real, preferred (ether) frame." Kept, corrected. FitzGerald & Lorentz first read it that way; the formula L=L₀/γ is exactly theirs, but Einstein made it frame-relative — no ether required.
The red team's move: flip the law to L = L₀·γ so the moving rod grows longer instead of shorter. The blue team's witness (window 7) is watching.
Replace 1/γ with γ and the rod stretches — the witness re-checks the known rod, finds L > L₀ instead of shorter, disagrees, and turns red. Nothing is faked; the attack is real and it is caught.