Water Cycle. The water cycle is also called the hydrologic cycle.
Climax. Climate changes can occur over long or short time periods.
Pluto. Pluto's orbit is so eccentric that it periodically passes inside the orbit of Neptune.
Keratin. A rhinoceros's horn is made of keratin.
Ores. Ores are rocks that contain important elements, particularly metals.
Armor. Modern law enforcement and military personnel wear body armor made of DuPont's Kevlar.
Pair Production Quantum Fluctuations. Quantum mechanics predicts that black holes emit radiation.
Ambient Air Temperature. On a typical day on Mercury the early-afternoon temperature reaches a high of 800 degrees Fahrenheit, hot enough to melt zinc and tin.
Sundial. The sundial is the most ancient of scientific instruments.
Spring Scale. A spring scale works by Hooke's Law.
Neritic Zone. The neritic zone is also called the "coastal waters".
Cnidarians. The group called Cnidarians includes jellyfish, coral and hydra.
Timebase Corrector. Time base correction is used to reduce or eliminate mechanical errors in analog recordings.
Fossil Record. The earth's fossil record provides information about evolution.
Chest X-Ray. The X-ray was invented by accident in 1895.
Soil Erosion. Extensive soil erosion resulted in the "Dust Bowl" of the 1930s.
Erosion. The Grand Canyon was made by erosion.
Very Fast Whitewater Cascade. Niagara Falls comprises the American and Bridal Veils Falls on the American side and the Canadian-Horseshoe Falls on the Canadian side.
Rings. One annual tree ring is composed of a ring of early wood and a ring of late wood.
Wind Tunnel. A wind tunnel is used in aerodynamic research to study how air moves over an object.