Yes, according to the theory of relativity, if a spaceship were traveling near the speed of light relative to an observer, the observer would perceive time passing more slowly on the spaceship due to a phenomenon known as time dilation. However, it's important to note that the term "moving slowly" can be misleading in this context.
From the perspective of someone on the spaceship, their own experience of time would proceed normally. However, for an observer outside the spaceship, watching it pass by at a high velocity, time would appear to be moving more slowly for the spaceship and its occupants. This means that from the observer's point of view, the spaceship would seem to be experiencing time at a slower rate compared to their own.
The apparent slowing down of time is a consequence of the constant speed of light in the theory of relativity. As an object approaches the speed of light, its relative velocity to the observer increases, leading to a greater time dilation effect. This effect becomes more pronounced as the spaceship's velocity approaches the speed of light, resulting in a significant difference in the passage of time between the spaceship and the observer.
So, while the spaceship would not appear to be moving slowly in a visual sense, an observer would perceive time on the spaceship as passing more slowly due to time dilation.