Fire rainbows are the rarest of all naturally occurring atmospheric phenomena. For a fire rainbow to occur, cirrus clouds must be 20,000 feet in the air with the precise amount of ice crystals, and then the Sun must hit the clouds at 58 degrees.
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German geologist and mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science.
Planets are turning out to be so common that to show all the planets in our galaxy, this chart would have to be nested in itself--with each planet replaced by a copy of the chart--at least three levels deep.
The Supercontinent Pangaea of the Triassic Period - A map of the Earth around 250 to 200 million years ago featuring Gondwanna, Laurasia and Pangaea the Supercontinent. Populated with Dinosaurs, Therapsids, Pterosaurs, and other prehistoric beasties.