Superman has no powers on krypton, but why on earth?

Superman has no powers on krypton, but why on earth? In the movie Superman: The Man of Steel, Joe-El played by Russell Crowe explained to the superman played by Henry Cavill: the natural environment of Krypton is much worse than that of the earth ... The earth star is younger and brighter than Krypton, and your cells absorb its radiation and strengthen your sensory muscles and skin; The gravity of the earth is smaller than that of krypton, and its air can nourish people more. I can't imagine you becoming so strong.

Superman, nourished by the yellow sun and fresh air, is indeed stronger than the Kryptonian headed by General zod who came to earth later. Although Superman's performance was not good at first, he became stronger and stronger in successive battles. In World War I, the town was suppressed by Feola alone. Later, Feola was too big to suppress, and finally he had to retreat back to the spaceship. In the decisive battle with zod, zod may still have a slight advantage in visual effects, but the final result is that zod was killed by Superman and completely defeated.

The characters in comics are very similar to those in real life, and the society in comics is similar to human society, but the basic science in comics is not far from human science. Gravity, friction and conservation of mass are not counted in comics, so Flash runs to talk to himself. The basic science in comics is "setting", which is not only chaotic, but also each comic can have its own rules. If judging by the standards of real life, it is almost invincible for children born in Krypton to go to the earth, then human beings can easily be killed by a small beetle when they go to Krypton. Can NBA players come to CBA and CBA players go to NBA to perform? Although Kryptonians look like earthlings, their bodies are actually much stronger than humans, but the environment and red sun of Krypton limit them. As long as kryptonians absorb yellow solar radiation, they are superhuman.