Relativity Park: Walking Speed of Light

Your velocity

0.00km/h

β: v / c: 0.0000
γ: Lorentz factor: 1.000
Lengths ahead: × 1.0000

Elapsed

Your watch: 0:00.0
World clock: 0:00.0

Galilean view (aberration off)

Arrows / W A S D: accelerate Mouse: look Space: stop L G C B: toggle effects R: reset

Light is slow here

In this park, the speed of light is 5 kilometers per hour — a brisk walk. Just like in the real world, the speed of light is not attainable, only approachable asymptotically. The more you speed up, the more relativistic effects will become apparent: length contraction, time dilation, Terrell rotation, etc. The Doppler effect of light also becomes apparent, with objects in front of you blueshifted, objects behind you redshifted, and transverse Doppler effects visible on objects in motion.

Settings

Effects Light-travel delay L You see each object where and when its light left it. Aberration & contraction G The Lorentz boost of apparent position. Doppler color C Spectra blueshifted and redshifted according to motion. Relativistic beaming B Light piles up ahead of you and thins out behind.

World

Speed of light5.0 km/h

Eye adaptation Your retina adjusts to the average brightness ahead.

Debug

Beaming exponentD^4.0

Exposure1.00

Render scale100%

Ground detailHigh

Adapt to speed Retessellate the ground with finer detail as the observer approaches c.

By Dmitry Brant, 2026
source code

Field guide

All of the motion effects you see are physically accurate, in a world where the speed of light is greatly reduced, so it can be observed more easily on human scales.

Controls

On touchscreens: use the left joystick to accelerate and drag the view to look around. Release the joystick to coast; tap STOP to halt. Hold Rise or Drop to change height. Reset returns you to the entrance.

W A S Daccelerate

↑ ↓ ← →accelerate

Mouselook around

Spacestop

Q drop / E rise

Rreturn to start

Tabsettings

Escrelease mouse

Effects

Play around with what effect causes which phenomenon to be observed.

Llight-travel delay

Gaberration & contraction

CDoppler color

Brelativistic beaming

Things to try

Accelerate by pressing the Up arrow. Your field of view begins to condense in the direction you are traveling, and becomes blueshifted. If you look behind you by using your mouse to turn, that field of view is redshifted and stretched out. This is relativistic aberration. Press Space to stop any motion, and observe how the field of view returns to normal.
The lamp posts all flash once per second of world time. Move toward a lamp and the flashing speeds up; move away and it slows down. Also observe the timers labeled "Your watch" and "World clock", and see time dilation in effect.
The Ferris wheel and carousel cars move at 75% of the speed of light. They are contracted by their own motion, and you see each one at a different moment in its trip around the circle. As the cars move around, you can see the effects of relativistic contraction and Terrell rotation.
The shuttle near the end of the corridor runs back and forth, also attaining a speed of 75% of the speed of light. Notice how it also contracts and undergoes Terrell rotation as it moves.

What's NOT accurate

Obviously a Ferris wheel spinning at relativistic speeds would fly apart, and if you travel through the atmosphere at relativistic speeds, you would be vaporized instantly. Even if you travel near the speed of light in interstellar space, you would be cooked by the cosmic microwave background radiation blueshifted to gamma rays.
The rendering of blueshifts and redshifts is a rough approximation. At extreme redshifts, the color fades to black. And at extreme blueshifts (past violet), the color turns to a metallic silver to represent x-rays, then to bright white to represent gamma rays (totally unphysical, but just to get a sense of it).

MOVE

Drag the view to look · Release to coast