Chapter 4, Problem 1RQ

Why did Greek astronomers conclude that the heavens were made up of perfect crystalline spheres moving at constant speeds?

To determine

The reason for Heaven's were mode of perfect crystalline sphere moving at constant speed.

Answer to Problem 1RQ

Greek Astronomers concludes that heavens are made of perfect sphere because heavenly bodies move in circular motion. The only perfect geometrical shape is sphere.

Explanation of Solution

• Heaven is a huge dome under which Sun, moon, stars, planets are situated. As sphere is a perfect geometrical shape, it carries a point on its surface around a circle anywhere and circular motion is the only motion which is uniform.
• Greek astronomers were highly interested in numbers and mathematics. They wanted to calculate heavenly motion of the object. They concluded that all the objects in heaven are attached to giant Sphere which rotates around Earth at uniform motion.
• Sun, moon, planets do not revolve around earth and don’t set and raise like sun, they just go laterally like a cap which turns half along head and back.

Conclusion:

Unlike set and rise of stars, heaven is perfect sphere of Crystal which moves uniformly at constant speed. Stars are attached to a rigid frame called heaven.