Doesn’t that mean that heat vision is capable of bypassing his invulnerability? Hair and skin are made of the same thing aren’t they? Also, if you go by the force field explanation for Superman’s invulnerability, his hair is close enough that it should be covered by the force field. What does this mean when Superman fights other kryptonians or other beings that have heat vision like Daximites or Bizzaro? Deep thought😄