Relativity is a philosophical thought and a concrete application of the principle of relativity in physics. However, our textbooks often turn relativism into absoluteness and treat it as an absolute concept. The more people learn, the more confused they become.
In relativity, velocity is the rate of change of the distance between two particles, which has nothing to do with the third party. The first sentence of the topic is "Two spaceships are in the same direction ...". Imagine if there were no other reference objects in the universe, which object would think it was moving? When you take yourself as the frame of reference, the only thing you can see is that other celestial bodies are moving. Assuming that the acceleration caused by gravity is not considered first, then, when two objects are in free fall at the same time and there is no other reference object for each other, what is the motion of the other?
Looking closely at Lorentz transformation, we can see that it will be slower to observe another system on a system with itself as the reference. Actually, I think the time is faster. This is a relative statement.
Just like when two screws and nuts don't match, the nut will be said to be big or small based on the screw and thick or thin based on the nut.
We see that people in the distance will be smaller than those nearby. If we take the size we see as the standard, people in the distance will become bigger. Because its initial velocity is greater than what we saw.
If we take people's body shape as the standard, we can only say that people in the distance have become smaller, because the people we see are smaller than the actual people.
Ok, now back to the topic:
1), the time T: 20 m /c from the stern to the front of the forward flight is time t, because C on any system is the same. This is the time measured on the spacecraft before.
2) Because the relative velocity of the latter spacecraft is 0.98, the observation time becomes longer: 20m /c/0. 199, that is, t/0. 199.
3) the observed speed of light on any system is c.