The San Andreas Fault is a continental transform fault, meaning the plates slide past each other along a fault line. It extends roughly 800 miles (1,300 km) through California and forms the tectonic boundary between the Pacific Plate and the North American Plate.

When most liquids are cooled, the particles settle into a regular order, and the liquid becomes a solid. But helium atoms are so light and weakly drawn to one another that even when ordinary atomic motions have quieted, the atoms jiggle with zero-point motion, a slight momentum imparted by the quantum uncertainty principle. Hence, they never settle into the solid state.

Halley's comet was recorded by Edmund Halley in 1682. It was seen again in 1758, 1835, 1910, and 1986 -- approximately every 76 years.

Burbank developed more than 800 strains and varieties of plants over his 55-year career as a botanist.

Sharks are older than trees. The earliest species that can reasonably be classified as a "tree," the now-extinct Archaeopteris, lived around 350 million years ago. But Sharks? They laugh at trees. They've been around for 400 million years. Insects broadly resembling cockroaches appeared around 300 million years ago. Early humans didn't appear until much later.

The moons of Uranus are named after characters from the works of William Shakespeare and Alexander Pope.

Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.

The chemical symbol Ag is from the Latin word for "silver" -- argentum.

Hydrogen is the lightest and most abundant element in the entire Universe, constituting roughly 75% of all baryonic mass.

The most common stalactites are speleothems, which occur in limestone caves. They form through deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions.