insulin
DNA's double helix
radium and polonium
relativity
penicillin
rotation of Earth
law of falling bodies
Halley's comet (orbit)
circulation of blood
cells
evidence of expanding universe
ring around Saturn
extraterrestrial radio signals
laws of planetary motion
nature of combustion
bacteria
laws of heredity
law of gravitation
microorganisms that cause fermentation
conditioned reflex
oxygen
transmission of yellow fever
X-rays
proton
Martian 'canals'
electron
deuterium
radiation belt around the Earth
plate tectonics
folic acid