Economics begins with the assumption that human actions are rational-intended for maximum self-benefit. For example, people pay more for a larger box of the same cer...

Characteristics of Tropical Rain Forests Almost all the action in a rain forest (not just photosynthesis but also flowering, fruiting, predation, and herbivory) happens high in t...

Martian Volcanoes       Earth is not the only planet to have volcanoes; in fact Mars-though all of its volcanoes have long been inactive-has the two largest ones i...

    How the First People Got to the Interior of North America   Most researchers believe that the first people to come to North America came from Asia to what is no...

The special character of the Nile, which made it central to ancient Egyptian culture, was its annual inundation (flooding). During June the river began to rise, and a quantity of g...

The Porcelain Industry at Jingdezhen Porcelain is a ceramic material that is prized for its translucence, hardness, and smoothness. Porcelainwas first produced in China, perhaps ...

Woody plants produce a great variety of chemical compounds to provide protection against other plants, diseases, and herbivores (plant-eating animals) big and small. These chemical...

Methane Hydrate as a Potential Fuel   At the bottom of the world's oceans lies a potential source of energy that could provide society with fuel well into the next century. Th...

The oldest Earth rocks known to date, found in Quebec, Canada in 2008， were determined to be about 4.3 billion years old. However, the oldest known materials of the solar system-M...

  During the European Renaissance (1300-1600)， artists in Florence, Italy, made striking use of oil-based paints, but the development of these paints was part of a long and c...