Momentum. Velocity, displacement, momentum, force and acceleration are vectors.
Stamp Collector. Philatelists study stamps as well as postal history.
Erosion. The Grand Canyon is one of the world's most staggering examples of erosion.
Medium. Electron pressure and gravity determine the size category of a star.
Duck-Billed Platypus. The duck-billed platypus is native to Australia and Tasmania.
Payload. "Useful load fraction" is the combined weight of the payload and the fuel.
Navy. BGM-109 Tomahawk was developed by General Dynamics and is produced by Raytheon.
Apollo 11. Apollo 11 landed on the moon July 20, 1969.
One-Sixth. The moon is 1/4 the size of Earth, so the its gravity is much less than the earth's gravity.
1/9th. Icebergs that come to rest on the seabed in shallow water can become an ice island.
Genetics. Gregor Mendel became interested in why things take on the traits of their parents, and began his research with plants.
10^5. A "newton" is named for Sir Isaac Newton, who discovered gravity.
Marble. Marble is a metamorphic rock composed of recrystallized carbonate mineral.
Index Fossil. Index fossils are used to define and identify geologic periods or faunal stages.
Pegasus. One of the stars in 51 Pegasi is orbited by the first true extrasolar planets ever discovered.
Apollo 8. Apollo 8 was the first human spaceflight to leave the orbit of the Earth.
Pluto. Since being declassified as a planet, Pluto's technical name is "134340".
A Tornado. "Gustnadoes" are small, weak tornadoes that do not stay on the ground for very long.
Atlantic Ocean. The Atlantic Ocean is divided by the equator to create the North Atlantic and South Atlantic oceans.
South Sea. Because of the calm waters, Magellan renamed the sea the "Pacific Ocean".