Inherent time refers to the event time recorded in a coordinate system with zero speed relative to the event location. Two things happened on the ship here. One thing is that the spacecraft found a comet, and the other thing is that the spacecraft exploded. If the ground is in the S coordinate system, the spacecraft is in the moving coordinate system S'. Obviously, the pilot in S', that is, the spaceship, is still relative to these two things.

In the theory of relativity, the difference and connection between the time and space coordinates of the same event observed in two coordinate systems S and S' with relative motion. In the content of time expansion, it is emphasized that the time interval measured in S' system is shorter than that measured in S' system. For example, one person on the ground determines an S series and one person on the train determines an S' series. If something happens in the same place on the train, for example, it takes 1 minute to light fireworks at X', then the interval between people on the ground and seeing it happen must be less than 1 minute.

Let's go back to the question of t=5s: Earth people found that the spaceship collided with a comet five seconds later, which means that two things happened on the spaceship. One thing is the discovery of a comet (which can also be considered as the initial moment), and the second thing is the explosion of the spacecraft. The time interval between these two events on the spaceship seems to be t = five seconds to the people on the earth, so how long does it seem to the people on the spaceship? (It is known that the speed of the spacecraft relative to the Earth is 0.6c), which is converted into the simplest question about time expansion. The time t measured in the inertial system S moving relative to the event position is longer than the time t' measured in the inertial system stationary relative to the event position. Now that we know that t=5s, then t'=?