The proof, in six diagrams

Each figure matches one step of the argument that an infinite no-three-in-line walk exists. All numbers shown are real, exhaustively computed values from the project (repo: github.com/ekalvi/erdos-193).

1 · The game: no three footprints on a line, ever

a legal walk — check every triple: none aligned violation — three footprints on one line
Footprints live on the integer grid; each hop comes from a fixed menu of 124 moves. The rule applies to every triple — including footprints laid thousands of steps apart. Question: can a walk go on forever?

2 · The machine: enlarge, twist, patch — repeat

seed (obeys the rule) enlarged ×3 + twisted (skeleton) patched with legal hops blue = inherited anchors · green = newborn patch points
One generation: every anchor position is the enlargement of an old footprint; gaps get 2–4 legal hops. Walk length ×3.4 per round. Verified runs: 20 → 62 → 214 → 715 → 2,457 → 8,292 → 28,271 steps, no failure ever.

3 · Born safe = safe forever

h = miss margin a trio that missed at birth → enlarge ×3 → 3h — margin GROWS the same trio, one generation later — safer, automatically, forever
Enlargement is a reversible linear map: lines stay lines AND non-lines stay non-lines (proven exactly; verified on millions of real triples with zero exceptions). So risk exists at exactly one moment per trio: birth. The infinite future is deterministic and safe.

4 · Death has one door: the graded corridor

grade 0 — safe, out of reach 90.2% of chord pairs grade 1 — leading digit matches 8.4% grade 2 — two digits match 1.28% grade 3+ … deeper … 0.18%, thinning ×8.5 per digit EXACT = all digits = collinear never observed (280B pairs) advance: ≤ 18% per round (worst case, proven over ALL states) rescue: ≥ 82% per round — the stitches re-scramble digits
Every possible violation must climb this ladder rung by rung — digits of direction-agreement can't be skipped. Each rung costs a ≤18% event while an 82% rescue pushes back. Reaching the bottom needs an infinite losing streak: probability zero per triple.

How to read this: a “grade” counts how many leading base-3 digits two chord directions share — grade 0 means they differ immediately (harmless), and exact collinearity would mean agreeing in every digit. Three facts make the ladder work. No rung can be skipped: one enlargement round can deepen agreement by at most two digits, and a birth can only write the last few digits (figure 5) — so any triple headed for collinearity must pass through every grade on the way down. Each rung is a toll: we computed, over every one of the 78,728 possible arithmetic situations (not a sample), that at worst 18% of stitch choices let a pair hold or deepen its grade — the other 82% kick it back up. The bottom is infinitely far: reaching “all digits” requires winning the 18% event forever — a probability-zero streak per triple. The percentages on the right are the measured population at each grade in the record walk; they thin by ×8.5 per rung, exactly matching the toll.

5 · Why births can't cheat: the digit lock

a newborn's chord direction, digit by digit (base 3): 2 · 1 · 0 · 2 · 1 ? · ? coarse digits: locked before birth (inherited from enlargement — untouchable) fine digits: writable (the only thing a stitch offset can change) to kill, ALL digits must match a line through two old footprints — impossible unless the coarse digits already matched.
A new point = enlarged parent + small patch offset. The offset edits only the finest digits, so a birth can only complete an alignment that was already a deep near-miss — the corridor's lower rungs. Grade-0 pairs (90.2% of everything) are physically out of range. Rare "born-deep" cases (0.097%) are counted separately.

Why this locks births out: a new point is always “3 × parent + small offset,” and multiplying by 3 in base 3 is a digit shift — it fixes the coarse digits before the stitch is even chosen. The offset (at most a few grid units) can only write the final digits. So for a newborn to land exactly on a line through two old footprints, the coarse digits of that alignment must already agree — which is precisely being deep in figure 4’s corridor. Grade-0 configurations (90.2% of everything) are unreachable by any birth this round, no matter how unlucky. The rare exceptions — births that land already deep, 0.097% measured — are counted as their own event family rather than swept under the rug.

6 · The finale: exponential toll beats linear entanglement

The Lovász Local Lemma needs e · pH · (d+1) ≤ 1: each H-round failure (pH ≤ 0.18H, shrinking exponentially) must be small against its entanglement (d ≈ 3(H+1)·6.5×10⁷, growing linearly). The curve crosses the threshold at H = 14: watching each newborn danger for 14 generations suffices for ALL dangers — infinitely many, across the infinite walk — to be dodged simultaneously. (Current status: constants certified; the semantic repair of the chain is in final build.)

This last step turns “each danger is individually dodgeable” into “all of them can be dodged at once” — the leap from probability to existence. The Lovász Local Lemma says: if every bad event is unlikely relative to the number of other events it shares decisions with, then some assignment of all decisions avoids every bad event simultaneously. Here the failure probability falls exponentially with the watching window H (×0.181 per round — the certified worst case), while entanglement grows only linearly in H against a fixed catalog of 6.5×10&sup7; templates. An exponential always overtakes a line: with our constants that happens at H = 14, where the criterion is satisfied with margin (0.33 ≤ 1). What closure buys, once the remaining theorems land: at every level of the construction a legal stitching exists; a final compactness argument (König’s lemma) then chains the levels into one infinite walk. Honest status: the constants are certified by exhaustive computation; the semantic containment linking them to the exact birth event is the piece currently being rebuilt after hostile review.

Companion page: the interactive amplification explainer shows step 2 with real coordinates you can click.