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Lightspeed Courier

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Lightspeed Courier

Deliver cargo in a ship flying at nearly the speed of light. Time slows down, space contracts and stars change colour — all by the theory of relativity.

  1. 1Hold the left mouse button — the ship turns to the cursor and fires the engine. Or W — thrust, A/D — turn.
  2. 2Space or S — brake: the ship turns against its motion by itself. The dashed “stop” circle shows where you would stop.
  3. 3Approach a station slowly to dock. There you take jobs and refill fuel and oxygen.
  4. 4Oxygen is used by the SHIP clock: the closer you get to light speed, the slower your time runs.
About, tips and FAQ

About the game

Lightspeed Courier is a science game about Einstein’s special theory of relativity. You pilot a courier ship that speeds up to nearly the speed of light and delivers cargo between star stations.

Every effect uses the real formulas. At high speed your clock runs slower than the galaxy’s (time dilation), space contracts along your path (Lorentz contraction), and the stars ahead crowd together and turn blue while those behind redden (aberration of light and the Doppler effect). You can never reach light speed: the closer you get, the harder it is to speed up.

These effects are the gameplay. Oxygen is used by the ship clock, express jobs run on the galaxy clock, and perishable cargo can only be delivered thanks to time dilation — a hands-on way to understand the twin paradox. Play free in the browser on desktop and mobile.

Tips

  • Brake early: the “stop” circle shows where the ship would stop if you started braking now.
  • You need fuel both to speed up and to brake — don’t burn the whole tank accelerating.
  • For perishable cargo, go faster: at γ = 2 the cargo ages half as fast.
  • Express jobs run on the galaxy clock — a straight route matters more than extreme speed.
  • Steer around asteroid clusters: a hit at high speed badly damages the hull.

FAQ

What is time dilation?
A relativity effect: a moving clock runs slower than one at rest. At 0.87c time on board runs half as fast (γ = 2), at 0.99c seven times slower.
Why can’t you reach the speed of light?
Getting closer to light speed takes more and more energy, and reaching it would take infinite energy. In the game your speed grows ever more slowly even though the engine thrust stays the same.
Why do stars change colour and gather ahead?
Aberration of light and the Doppler effect: light from stars ahead arrives at a different angle and a higher frequency (bluer), light from behind at a lower one (redder).
What is γ (the gamma factor)?
The Lorentz factor: how many times slower time runs on board and how much space contracts along the motion. γ = 1/√(1 − v²/c²).