Question

Which of the following provides clear evidence that the universe is expanding ?

• A. the Oort cloud
• B. the Kuiper belt
• C. Saturn's ring
• D. Halley's comet
• E. the red shift of distant galaxies

Answer 1

The correct option is E the red shift of distant galaxies

The spectrum of light coming from galaxies have spectral lines of hydrogen ,sodium etc. We compare the spectral lines obtained from galaxy to the spectral lines obtained in laboratory of the same element .If the spectral lines of galaxy are shifted towards the red end of the spectrum (red shift) it means the galaxy is going away from earth . This implies that universe is expanding .This is one of the applications of Doppler's effect .