Self-evidently, the gravity on the surface of a planet limits the maximum size of large terrestrial organisms.
As we have seen so far in this series, fire was an absolutely crucial component in humanity’s rise to civilization and technology.
As symbols of the perfection of human form, one might consider the Venus de Milo or Michelangelo’s David. But those don’t show the insides.
The firm belief in extraterrestrial life — a belief nearly universal in the scientific community — is an act of faith.
The metal element 42, molybdenum, is needed in the body in extremely small but vital amounts for enzymes to work properly.