The Early Iron Age     During the Bronze Age (roughly 3300-1200 B.C.E. in the Middle East), civilizations were limited in their use of iron. Most iron occurred not in ...

重复时间 2024-06-18 2024-09-28 2025-02-22 Equestrian Portraits in the Eighteenth and Nineteenth Centuries     It was common for European rulers from the eighteenth ...

The Moon's Origin   One of the earliest scientific theories about the Moon's origin postulated that Earth and its moon formed out of a dust cloud alongside one another, much a...

The Origin of Mars's Moons     Mars has two tiny moons, Phobos and Deimos. The orbits of both these satellites are nearly circular and close to the planet: Phobos orbits...

Why Did Agriculture Arise   Sometime around 10,000 years ago, some hunter-gatherers took up agriculture. Though the advantages may seem obvious, there are also disadvantages: ...

Opera in Seventeenth-Century Venice     Opera, a form of drama set to music and featuring vocal performance supported by an orchestra, was born in Italy at the very end ...

  Periglacial Mounds   Periglacial regions are cold-climate areas that are located near the margins of glaciers-permanent ice sheets covering parts of the Arctic and ot...

The American Hospital     Few institutions have undergone as radical a transformation as the hospital has in its modern history. It is perhaps distinctive among social i...

The Azolla Event     During the early Eocene period, about 56 million years ago, Earth's atmosphere had high levels of carbon dioxide(CO2) which warmed the planet. But a...

The Deforestation of England Today's typical English countryside of rolling green fields and few trees did not evolve naturally. England was originally wooded. Forests of oak and ...