What is the hardest thing on earth besides diamonds?

What is Neptune's moon proteus like? Is John Glenn the oldest? Which planet would you double your weight on? Why does the sun affect the tides less than the moon does? What is the light of fire a symbol of? What observe lens should be used when you first look at a specimen under the microscope? What part of a rocket allows it to blast off and rise through the atmosphere? Why do you see objects as upwright and of the same size although the images formed on the retina are upsidedown and diminished? Have humans or human-made objects traveled to mars or on it? What do the creeds tell us? The orbits of planets being elliptical was one the planetary laws developed by? What term is defined as a steady or fluctuating pinpoint of bright light that does not go away when all light is blocked from the objective lens? What was Zeus afraid of? How many light years away from earth is galactic center? How can solar raddii be used to describe the sizes of stars including the subgroups of white dwarfs giants and supergiants? What does the little horseshoe mean on a light bulb? Which dwarf planet is closer than Neptune 10 percent of the time? What state does the Space Shuttle usually take off from? How much does an annual subscription to galavision cost? Where scanning is used?