Re: Kryptonian Physiology in Man of Steel
Here's my take on the subject. I believe the people of Krypton had super powers at one time. I believe after their sun became older, it lost the ability to give out certain rays that gave them powers. It also change the gas composition in the atmosphere. Which means Krypton's atmosphere is different from that of earth. At the same time, they are educated in science, math, and other forms of knowledge like earths'. They also space travelled. After they lost their powers, they increased their knowledge in science, biology, psychology, and math to compensate so they wouldn't be vulnerable to attacks from other planets. They developed advance technology, computer systems, far beyond earth so it can help in it's efforts. This is why I think they knew how kryptonians would respond to earth's atmosphere. Their battle suits were specially designed to mimic super feats like a kryptonian who absorbed earth's yellow sun without affecting them.
Earth's atmosphere or gases when breathe aids in a Kryptonian power. Alone with the rays from earth's sun. Krypton's gravity is 1,000 times greater than of earth's. Which means Kryptonian bones and muscles need to be 1,000 times denser than a human. Kryptonians have a well-developed psychology beyond humans. They learned how to control their bodies with their minds. Which might explain how Clark is able to fly. It's similar to Chi-power in martial arts. This is why when Zod brought Clark aboard the ship he was affected by the change in the atmosphere. Plus, Zod was able to probe Clark and Lois's minds.
It's earth's gases combined with the sun rays that super-charge a Kryptonian. Clark's body does absorb the sun's energy. Since he can control his own physiology he can shoot fire from his eyes. This is very scientific and grounded in realism.