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Projects / A93-09

Nanosecond

A running app that measures how much time relativity saves you on every run.

Part no.
A93-09
Status
prototype
Platform
iOS
Year
2026
Stack
SwiftSwiftUISwiftDataCloudKitStrava API
≈0.32 psTime "saved" per hour of running
γLorentz factor, every GPS fix
92Swift files with unit and UI tests
01 — The problem

Every running app shows the same numbers. Nobody gives you something new to be proud of.

02 — The case for it

A playful hook built on real physics. Your clock really does tick slower when you run, and Nanosecond turns that into a stat you can share, compare and race.

03 — Back of the napkin
Back of the napkinRough · not a forecast

A novelty with a social hook: free to try, with a paid "Field" for leaderboards and twin challenges.

  1. Downloads (assumption)20,000
  2. ×Upgrade for the Field3%
  3. =Payers600
  4. ×Price after Apple≈ €2.50 one-off
  5. =Revenue≈ €1,500
Running costs
Sync
CloudKit, free tier
Strava upload
free API
At 10× / 100×

CloudKit costs scale with Apple, not with me. Its real value is shareability: "I gained 0.3 picoseconds this morning" is a post that spreads itself.

Verdict

Not a business. It’s a brilliant hook, and could be a feature or a marketing stunt for a bigger running app.

04 — How it works
Diagram · From GPS to time dilation
  1. 01VelocityGPS speed in an inertial frame, corrected for Earth’s rotation.
  2. 02Lorentz factorγ = 1/√(1−v²/c²), integrated over the whole run.
  3. 03Proper timeThe gap between your clock and a clock left at home.
  4. 04FieldA twin-divergence view and leaderboard, synced with CloudKit.
05 — On screen
“What if running could buy time?”
“What if running could buy time?”
A live run, counting femtoseconds
A live run, counting femtoseconds
Your stay-at-home twin and the time you’ve gained
Your stay-at-home twin and the time you’ve gained
Design spec: recording, twin divergence, personal best
Design spec: recording, twin divergence, personal best
Route map states: net rate, GR cost, direction
Route map states: net rate, GR cost, direction
06 — Engineering highlights
01

Physics you can check

The project doc derives the Lorentz factor step by step and sanity-checks the result: about 0.32 picoseconds saved per hour of running.

02

Strava-ready

The upload integration is designed around a backend job queue, so it survives flaky networks.