Chapter 15, Problem 73A

To determine

To explain: The astronomers conclude that the distant galaxies are moving away from the earth.

Explanation of Solution

Introduction:

The phenomenon where light from an object undergoes an increase in wavelength is called redshift.

Redshift describes how light shifts towards longer wavelengths. When an object moves away from us, its light moves away from us hence its wavelength increases. Longest wavelengths are towards the red end of the spectrum. Since the light coming from distant galaxies appear redder than light coming from nearer galaxies, the astronomers can conclude that the distant galaxies are moving away from us.

Conclusion:

Redder lights indicate increasing wavelengths.