All on = the model's received-light prediction, with approximate materials and lighting. Switching one effect off makes a diagnostic view; the resulting pictures do not split into additive contributions. The two foundations are finite light travel time and the Lorentz transformation between you and the city. The six modeled consequences are listed in 🚲 Three pictures → 📋 Effects.
City geometry · compare the same viewpoint
All effects models a received-light image. Classical (Newtonian) uses ordinary perspective and instant light, with rest-size cars and a same-speed pacer 14 m ahead. Contraction only is a source-colour spatial diagram at one observer-frame instant, not a photograph.
The comparison shares one camera and field of view. Both effects (top left) uses the relativistic received-light geometry; Classical (Newtonian) (top right) uses instant light and rest-size objects; Length contraction only (bottom left) is a diagram of one observer-simultaneous slice. The bottom-right light-time-only view is a hypothetical, uncontracted city with finite light speed. It is available only as a paused snapshot below γ = 5: its moving cars do not yet form a consistent alternate history, and high-speed surface visibility is not fully validated. Source colours help compare shape; signal states can also differ because the sampled emission times differ. Doppler on adds the spectral shift to the top-left pane, and Full light adds beaming and modeled thermal emission there. The separate Car-body control above changes only moving-car body length. Wet-road reflections are off in this comparison; exposure can be matched or metered separately for readability.
Light from the side reaches you from further ahead, so the world squeezes into a forward window. This is effect 2 (turn and stretch: light travel + Lorentz transformation) described from your moving frame, not a separate effect; the switch splits it off as a diagnostic.
Approaching light is squeezed to shorter wavelengths (bluer), receding light stretched (redder), including infrared and ultraviolet sliding into view.
Light ahead is concentrated and more energetic, D⁴ brighter. Behind, D⁴ dimmer.
You see each car and signal as it was when its light left. Off shows where things are right now (impossible to see).
The city's own 287 K infrared glow. Invisible at rest; at 0.95c ahead it is shifted into visible light.
Light sources · switch each on or off
Street lamps, headlights, sky and sun bouncing off paint, asphalt, glass and leaves. Each material has its own reflectance from UV to near-infrared.
Windows (tungsten or LED), neon tubes, traffic signals, car lights, screens and the LED lines in your lane. Each has its own spectrum.
The 2.72548 K glow of the early universe, all around you. Its temperature shifts up with γ, but in this model the air hides it from the eye until γ of several thousand.
Point sources: their total flux grows like D² ahead (D³ per wavelength).
Time of day
Speed of light in this city
The scaled-light teaching model turns c down to 45 m/s (162 km/h) so the traffic is relativistic and light travel times are visible; c is the same in every teaching view and only β = v/c varies. With real c, cars and signals are nearly frozen, because time is slowed (by c/45 m/s, 6.7 million×) so you can still move.
View
Keys
W/↑ faster · S/↓ slower · Space stop · drag to look · 1–4 ahead / left / right / back · M mirror · C compare · F light fronts · E effects · P pause · J auto slow motion (Object lab) · B effect layers: rotation / beaming / both (Object lab) · . step one frame · N next chapter · U hide panels · Esc close panels · Tab moves between buttons
☢ Beyond RGB · radiation lab
Your eyes see only 380–780 nm. Here you control what radiates, how you see it, and what it does to your pod. Every number is live.
City temperature 287 K
How you see
Torches set into your lane
Spectral street
Real line lamps on the highway barriers (infrared, ultraviolet, X-ray), each the star of one speed; boards over the avenue and façade murals painted in heat, near-infrared or UV ink: blank at rest, readable only through Doppler.
Radiation on your nose
Nose temperature 290 K
A reference calculation (v8.15): the power per m² on the front of your pod, in your frame, from a graybody street canyon at the city temperature plus the CMB. It does not follow the source switches (those only hide light from the camera), lamps, traffic or the Object lab. The nose temperature relaxes toward its radiative equilibrium; it is not a heat-capacity model, and none of this is a radiation dose.
✓ Try this ·
Each item ticks itself when you do it. "Take me there" sets up the speed, view and settings for you.
What you are seeing
Spectrum probe · a source at rest in the city, along the crosshair
A calculator, not a sensor: it does not identify the object under the crosshair or its motion (a moving car adds its own shift). Cyan: the source's rest spectrum as λ·Sλ (power per ln λ, normalised). Shaded: the part that lands in your eye, coloured as it arrives. Dashed: your eye's own 380–780 nm.
SAME SPOT, FOUR SPEEDS · four observers pass this point at the same instant · same camera · same instant
0near c
Presentation mode · W / S speed · arrows or 1–4 look · P pause · V or Esc to leave
Up to three objects pass you, away from the city. Each point is drawn where its light left it, in its own colour, through the real spectra.
Try an experiment
Who is at rest with the floor, light and sky?
Light
Objects · speed relative to you
Camera and time
What to switch
Brightness · from γ 1000 down to 10⁻²⁴ across one view
Undo beaming 0 %
Separate the effects on the shape · two compete
Ghost overlay
Morph seen
Newton → measured (contraction) → seen (light travel time). Smooth for the wheel; other objects switch halfway.
LEFT EYERIGHT EYE
Mechanics · what the object itself feels
Material
ⓘ Idealized rolling wheel. In the hub's frame it turns rigidly (a true circle, straight spokes, rim speed v); each point's worldline is then Lorentz-transformed exactly and drawn at its own light-delay time. So the contact point is at rest, the top moves at 2v/(1+v²/c²), the outline is the circle contracted by the hub's γ along the motion, and rim material is spaced by its own speed. A real material wheel could not be spun up to stay rigid like this near c (Ehrenfest paradox).
PLAY WITH THE NUMBERS · the speed of light c is fixed
Measured clock rates in one frame. Switching restarts the comparison with the other frame’s simultaneity.
keys: → next · ← back · Esc exit
keys: → next · ← back · Esc exit
Claude Edition v8.38.2 · real-time special relativity
SPEED OF LIGHT CITY
In this city, light crawls at 162 km/h. Drive the elevated highway up to γ 600,000 and watch red lights turn green, the street fold into a tunnel, and the city's own heat start to glow.
W / ↑ accelerateS / ↓ slow downdrag to look1–4 ahead · left · right · back
Every colour is computed from a spectrum, so nothing is tinted. Aberration, Doppler, D⁴ brightness, light travel time, Lorentz contraction and time dilation follow the exact formulas; the city they act on is a model (see What's NOT accurate).