Why does the rocket burn red when it returns to earth?

The time for the rocket to fly away from the earth and come back at a constant speed is really equivalent to the time for the earth to leave the rocket at the same speed and approach the rocket at the same speed. During this period, the rocket's time to see the earth slowed down, and the rocket's time to see the earth slowed down by 0.6 times.

However, the key is the time to "turn your head". When the rocket rotates at a uniform speed, it is a process of general relativity. According to the gravitational time expansion of general relativity, gravity and acceleration are equivalent, and the time of the party with greater gravitational or acceleration force will be slower.

This gravitational time expansion is not mutual. Although both the earth and the rocket saw each other slow down and stop and then accelerate to approach each other, people on the earth saw that the rocket was acted upon, and people on the rocket saw that they were acted upon, but the earth was not acted upon.

So people on the earth watch the time on the rocket slower than themselves, and people on the rocket watch the earth faster than themselves. The final time is the result of the superposition of velocity time and gravitational time.

This process is also confirmed by experiments. The gravity on the ground is large, but the gravity in space is small. On the earth, the time to watch satellites in space should be faster than that on the ground, and the time to watch satellites in space is slower than that of oneself.

There is a relative speed between the satellite and the earth, so we should also consider the influence of speed on time. Finally, time on the satellite is faster than time on the ground. The clock of GPS satellite is faster than the ground and needs to be calibrated according to the theory of relativity.

I know when the resistance (dynamic pressure) is the greatest (and it should also be the time when the heat is the greatest? From the point of view of work, it is, but I don't quite understand it. Generally, it is the biggest when nodding at an altitude of 10 km. For example, the space shuttle is usually 1 1 km, the Apollo mission is about 13km, and now the Falcon 9 of Space Exploration Technology Company is about 13km.