Chapter 15, Problem 27A

To determine

To Explain: When someone looks out into the universe, he/she sees into the past.

Explanation of Solution

Introduction:

According to Albert Einstein’s Special theory of Relativity, speed of light is ultimate speed for the moving matter. The light can travel with the speed of 300000 km/s.As this is the highest speed that a particle or light can achieve, it requires certain amount of time to travel from one place to another place.

When observer looks out into the surrounding, the light reflected from the object incident on the observer’s retina gives the sensation of the object. Suppose the observer saw a star in the sky which is 10 billion light years from the earth.The time taken for light to reach the person from star is 10 billion years. So, star seen by the observer presently is not the actual star, but the star 10 billion years ago. With similar analogy, every object around seen by naked eyes is the object certain time ago, because light takes time to reach eyes.

Conclusion:

Therefore, when universe is seen by the observer, light takes time to reach from object to person. Due to that reason,when observer look out into the universe, he/she sees into the past.