Consider Galileo’s method of measuring the speed of light using two lanterns. To get an accuracy of about 10%, the time taken by the experimenter in closing or opening the shutter should be about one tenth of the time taken by the light in going from one experimenter to the other. Assume that it takes 1/100 second for an experimenter to close or open the shutter. How far should the two experimenters be to get a 10% accuracy? What are the difficulties in having this separation?

Question

Philoid · Accepted Answer

As we know,

Speed of light = 3 × 10⁸ ms^-1

According to the question,

To get an accuracy of about 10%, the time taken by the experimenter in closing or opening the shutter should be about one tenth (1/10) of the time taken by the light in going from one experimenter to the other.

⇒ Distance travelled by the light in 0.1s = 0.1s × 3 × 10⁸ ms^-1

=3×10⁷ m

=3×10⁴ km

Hence, difficulty in separation of that distance will be the curvature of the earth. As we know, the shape of the earth is an oblate spheroid, it has a curved surface. Because of the curvy property, light from one of the experimenters won’t reach the other.