(Encyclopedia) cobalt, metallic chemical element; symbol Co; at. no. 27; at. wt. 58.9332; m.p. 1,495℃; b.p. about 2,870℃; sp. gr. 8.9 at 20℃; valence +2 or +3. Cobalt is a silver-white, lustrous,…
(Encyclopedia) rainbow, arc showing the colors of the spectrum, violet inside and red outside, which appears when the sun shines through water droplets. It often appears while the sun is shining…
1998 News Month-By-MonthWorldChina to Improve Human Rights (Oct. 5): Signs major international agreement that includes ban on arbitrary arrest and torture, and protects freedom of thought,…
By choosing a lifestyle that avoids certain risks, you can help protect yourself from developing cancer. Many cancers are linked to factors that you can control. Tobacco. Smoking and using…
(Encyclopedia) science fiction, literary genre in which a background of science or pseudoscience is an integral part of the story. Although science fiction is a form of fantastic literature, many of…
(Encyclopedia) shark, member of a group of almost exclusively marine and predaceous fishes. There are about 250 species of sharks, ranging from the 2-ft (60-cm) pygmy shark to 50-ft (15-m) giants.…
