Which describes what an outside observer at rest would observe about a spaceship that speeds up and approaches the speed of light?

As the spaceship’s speed approaches the speed of light, special relativity predicts that its moving clocks appear to run more slowly to the outside observer. The spaceship’s length along its direction of motion also appears shorter, an effect called length contraction. So the correct choice is “Time moves more slowly on the spaceship, and the length of the spaceship decreases.”

AI-written and checked against the verified answer.