Time Machine whirls back over eight centuries to 1000-1200. Ancestral Puebloans are living in the cliffs of Mesa Verde. Elsewhere in the world:

1) Mongolia: Warrior-emperor Genghis Khan has united tribes in Asia to build the Mongol Empire. Extended families, known as clans, make up those tribes. They live in yurts—felt-lined, circular tents. They are nomads, always on the move. Horses are central to their way of life. Children learn to ride and shoot a bow from a galloping horse.

2) China: There are 100 million people here—more than a million in one city! Emperor Huizong of Song promotes poetry, painting, calligraphy, and music. The Chinese have schools, a legal system, paper money, and many inventions.

3) Mideast: Muslims have conquered the land of Palestine. The head of the Catholic Church, Pope Urban II, has launched the Crusades. Ordinary people and armored knights are answering the call to war in an effort to recapture the Holy Land for Christianity.

4) South America: People of the Inca Empire don’t ride horses or use animals to pull plows. They have no metal tools or weapons, and no systems of writing or money. But they are creating huge stone structures and many roads.

5) Africa: Sundiata Keita is uniting the Mandinka tribes of West Africa into the Mali Empire. Gold, copper, and salt are mined. Salt is used as money and is worth more than gold.

6) Scandinavia: The end of the Viking era is near. Vikings will one day be glamorized as warriors. But most are farmers. Vikings wear leather, fur, wool, and linen. They use their metalworking skills for weapons and tools, but also for the jewelry that both men and women wear.

7) England. It is the Middle Ages. The king and lords own all the land. The rest of the people are poor. They rely on the landowners and their castles for protection. England’s King John will soon sign the Magna Carta. It will be remembered as a first step toward a new kind of government, where the power of rulers is decided by the people.