・The theory of relativity includes “special relativity,” which has the theme of “time and space,” and “general relativity,” and “general relativity,” which adds the keyword gravity to this, of which special relativity can be fully understood with middle school level mathematics. General relativity is such a difficult theory that it is sometimes difficult even if you go to the physics department at a university (p14)
・The three points of special relativity, 1) time delay, 2) shrinkage of space, 3) energy = mass, and time delay mean that what is being done appears to be delayed in time (p21)
・Relative speed is “the speed that an exercising person feels when they see someone doing another exercise” (p39)
・The speed of light at 300,000 kilometers per second is the upper limit of the world's speed, and light can move at that speed. “Mass” indicates “the difficulty of moving things,” and since light has “zero mass,” such a special thing is happening. An object whose mass is not 0 is said to never reach the speed of light even if it approaches high speed (p52)
・When the speed of light is fixed, what must be changed is “distance” and “time,” and there is a fact that “even at the same time is relative, not absolute,” as long as the principle of invariable speed of light is established (p74)
・When the speed is 80% of the speed of light, TA=√ (1- (V/C) ^2・TB, V=0.8C), 1 second of the person observing is 0.6 seconds of the person moving, so TA=0.6TB (P109)
・The difference in how people age between people who are moving and people who are at rest is that when they return to Earth on a spaceship with a speed close to the speed of light, it happens that people around you are much older than you (P113) You can only feel the delay in time when you can do it at a speed close to high speed (P115)