You fly a rocket along one straight line. The cruise-speed slider sets the speed you want: the center is stopped, right flies right, left flies left. Its scale is logarithmic in proper velocity γv, from about 1 m/s near the center to γ = 2×10¹⁹ at the ends; at high speed each step is the same change in rapidity. The rocket eases to the new speed, and the readout shows the push you feel while it does. Hold ◀ or ▶ to slide the target, or tap Stop.
The camera keeps a fixed zoom. Length contraction does the zooming: the faster you go, the more of the universe squeezes into view. Use − and + to change the zoom, and Reset to go back. The bar above the controls shows your progress toward the edge on a log scale.
Instant-sight shows where everything is right now in your rest frame. Distances and sizes shrink by γ. Real-sight shows where the light reaching you right now was emitted, in your rest frame, with its Doppler color shift. Ahead looks stretched and blue, behind looks squeezed and red. Light shifted far outside the visible band is drawn as a faint ghost.
The model is flat spacetime: no gravity and no cosmic expansion. Every object sits at its true distance from the Sun with its true diameter. Venus, Mercury, the Sun and the near half of the Milky Way are to the left; everything else is to the right. Far objects use light-travel distance, and the edge is 13.8 billion light-years away. Spiral-arm positions, galaxy light profiles, quasar host sizes and the background stars are approximate or procedural.
Position is stored as an exact integer number of millimeters, so you can stop anywhere, even next to a quasar, and still see millimeter detail.
Bodies are drawn as disks. Motion squeezes only the direction of travel, so in instant-sight a fast-moving planet becomes a thin ellipse, then a pancake. Near light speed things cross the view in a blink. If you want to watch one squash, tap 1× to slow playback to 1/10, 1/100 or 1/1000; tap again to cycle back. Your clock always reads true proper time. Your rocket is drawn life-size: 50 m long and 9 m wide. At most zooms it is far smaller than a pixel, so amber marks show where you are.
Keys: ← → change speed, space stop, V switch view, + − zoom, 0 reset zoom, T slow motion, P pause. Pinch or scroll to zoom.