third planet from the Sun and the fifth in the solar system in terms of size and mass. Its single most outstanding feature is that its near-surface environments are the only places in the universe known to harbour life. It is designated by...

Abnormal eating patterns, including anorexia nervosa, bulimia, compulsive overeating, and pica (appetite for nonfood substances). These disorders, which usually have a psychological component, may lead to underweight, obesity, or malnutrit...

Global warming is an extremely severe problem facing the world today. Its effects and causes have been on the rise and people need to do something about it before the problem gets any worse. Global warming is an increase in the earth's te...

Capacity for doing work. Energy exists in various forms—including kinetic, potential, thermal, chemical, electrical (&see; electricity), and nuclear—and can be converted from one form to another. For example, fuel-burning heat ...

political and ethical movement that seeks to improve and protect the quality of the natural environment through changes to environmentally harmful human activities; through the adoption of forms of political, economic, and social organizat...

Practice of obtaining military, political, commercial, or other secret information by means of spies or illegal monitoring devices. It is sometimes distinguished from the broader category of intelligence gathering by its aggressive nature ...

In today's society, there are many ethical issues on the Internet. Some of the biggest issues and concerns seem to be hacking and viruses, copyright infringements, spam, privacy, and cyberporn. Internet ethical issues affect a wide variet...

Differences exist among ethnic and cultural groups in their use—and abuse—of drugs and alcohol, as well as among risk factors that precede use and responses to treatment. Research suggests that an approach known as cultural c...

subtropical saw-grass marsh region, a “river of grass” up to 50 miles (80 km) wide but generally less than 1 foot (0.3 metre) deep, covering more than 4,300 square miles (11,100 square km) of southern Florida, U.S. Through it, ...

The plan was originally constructed by the first President Bush back in 1989, and called for a human landing on Mars no later than 2019. However, the requirements for such a trip were too extreme for the plan to be carried out. The 400 bill...

The word "extremism" is used to identify people, ideologies, or organizations that differ radically from mainstream society to such an extent that they are seen as existing on the margins of that society. This term, however, is applied by...