Chapter 14, Problem 1RQ

How does the darkness of the night sky tell you something import ant about the Universe?

To determine

To explain the darkness of the night sky, provide what important information about universe.

Explanation of Solution

Introduction:

If we look in any direction in the night sky our line of sight ends at surface of stars. Similarly, our universe is isotropic it looks similar in all directions. It is filled with stars.

According to cosmological theory our universe is not infinitely old and static. If we explore the night sky more distant stars are far away from us. Their star light is unable to reach us because of inverse square law their brightness decreases. In the same way if we look in the past to predict the beginning of the universe we see the time before the first star is formed.

Conclusion:

The darkness of star shows that the universe is not infinitely old it came into existence from some finite time in the past.