Chapter 15, Problem 29A

If you were in a high-speed spaceship traveling away from Earth at a speed close to that of light, would you measure your normal pulse to be slower, the same, or faster? How would your measurements of pulses of friends back on Earth be if you could monitor them from your ship? Explain.

To determine

Whether the normal pulse rate of person faster, slower or remain same when travelling away from earth in high-speed spaceship.

To Explain: The measurement of pulse of friend who is on the earth when person moving in spaceship.

Explanation of Solution

Introduction:

According to Einstein’s special theory of relativity, time is not absolute. When object moves with speed comparable to the speed of light, time in the moving frameslows down.

According to the first postulate of Einstein’s special theory of relativity, all the laws of physics are invariant in allthe inertial frames of reference. The inertial frame is a reference frame in which Newton’s laws of motion are valid. In another words, inertial frame is non-accelerating frame. Person who standing on the earth, observed the person in spaceship is moving. The normal heart rate of person in spaceship remains same measured inside the spaceship, because person is in inertial frame of reference.

The difference in reading observed because of the nature of observer’s frame of reference. Similarly,when person’s friend is on the earth and person on the spaceship monitored his pulse rate, person in spaceship observed that the earth is moving with respect to spaceship and heart rate of his friend found out to be slower. This is because with respect to person in spaceship, frame of reference of his friend is moving.