Nicolaus Copernicus was very frightened when he found all his calculations led to the same     1     (conclude) that the earth was not the center of the solar system. Only if you put the sun there did the movements of the other planets in the sky make sense. Yet the     2     (power) church believed God had made the world and     3     that reason the earth must be the center of the solar system.

Copernicus collected observations of the stars and used all his mathematical knowledge     4     (explain) them. But only his new theory could do that. He worked on his theory, gradually improving it. He placed     5     fixed sun at the center of the solar system with the planets going round it and only the moon still going round the earth. He also suggested that the earth was spinning as it went round the sun. In 1514 he showed his theory     6     (private) to his friends, who encouraged him to publish his ideas, but Copernicus was cautious and was afraid of getting     7     (attack) by the Christian Church.

The Christian Church rejected his theory,    8     (say) it was against God's idea. Yet Copernicus' idea is now the basis on which all our ideas of the universe     9     (build). His theory replaced the Christian idea of gravity,    10     said things fell to earth because God created the earth as the center of the universe.

A deafening boom roars through Pompeii's crowded marketplace. The ground shakes     1     (violent), throwing shoppers off balance. People scream and point toward Mount Vesuvius, a massive volcano     2     rises above them.

Nearly 2,000 years ago, Pompeii was a busy southern Italian city. But in 79, the nearby Mount Vesuvius volcano erupted. Almost overnight, Pompeii and many of its 10,000 residents disappeared under     3     blanket of ash.

Pompeii was basically forgotten until it     4     (rediscover) in 1748. Thanks     5     diggings, scientists have been able to figure out almost exactly what happened on that terrible day.

After the volcano first erupted shortly after noon, the thick ash turned everything black. Some residents escaped the city, while others took shelter in their homes. But the ash kept     6     (fall). Piles grew as deep as nine feet in some places, blocking doorways.

    7     (base) on what they uncovered, scientists believe that Pompeii was a prosperous town popular with     8     (wealth) Romans. Well-paved streets had high sidewalks. To relax, people soaked in public baths and enjoyed plays in two theaters.

Pompeii may be ancient history, but scientists are pretty sure Mount Vesuvius is overdue for another major     9     (explode). Luckily the people living near the volcano today will likely receive     10     (warning) before it blows.