To chase a sunset on Venus forever, you only need to walk 3.1 mph. But you'd have to head east, and instead of a glowing sun, you'd be outrunning a wall of pitch blackness.
Venus is the only planet in the solar system that rotates backward, a quirk known as retrograde rotation. Because of this, the sun rises in the west and sets in the east. To match the speed of this reversed rotation, a traveler must keep moving east.
Venus rotates exceptionally slowly, taking 243 Earth days to complete one spin on its axis. Because the planet is also moving around the sun, a full Venusian solar day—the time from one sunrise to the next—lasts 116.75 Earth days, or 2,802 hours.
The planet’s circumference at the equator is 38,025 kilometers. Divide that distance by 2,802 hours, and the terminator—the line separating day and night—moves at 13.5 kilometers per hour (8.4 mph). This is a fast jogging pace for a human, which is too fast to sustain indefinitely.
Planets are spheres, meaning the circumference of the latitude lines gets smaller closer to the poles. By the time a traveler reaches 68 degrees latitude—about as far north as northern Alaska on Earth—the shadow line slows down to just 5 kilometers per hour (3.1 mph). At that latitude, maintaining an average walking pace is enough to keep pace with the planet's rotation.
While the math works, the physical reality of Venus would stop any attempt. The atmosphere is so thick that surface pressure is 92 times that of Earth, roughly equivalent to being 900 meters underwater. At this pressure and at the planet’s average surface temperature of 465°C (869°F), carbon dioxide becomes a supercritical fluid. Moving through it would feel like wading through a chest-deep swimming pool of thin syrup, making a 5 km/h walk physically impossible.
Even if a traveler could survive the conditions, there would be no distinct sunset to watch. The dense sulfuric acid clouds block 90% of incoming sunlight and scatter the rest so heavily that the sun is never visible as a defined disc. The sky would simply remain a featureless, murky orange gloom until the terminator line finally caught up, plunging the landscape into total darkness.