Plastic Rings. The Great Pacific Garbage Patch contains millions of "six-pack" rings, milk jug rings and plastic bags.

Alternating Current. Nikola Tesla invented the alternating-current generator; in 1893 Westinghouse used AC to light the World's Columbian Exposition in Chicago.

Yuri Gagarin. On April 12, 1961, Yuri Gagarin of Russia became the first person in space.

Wind. Chinook winds are strong, dry winds found in the American West, where the prairies meet the mountains.

Axons. The axon project from the neuron to conduct electrical impulses.

A Tornado. "Gustnadoes" are small, weak tornadoes that do not stay on the ground for very long.