Question 1
To determine whether a celestial body is approaching or receding from Earth, astronomers employ ________.
◦ Einstein's equation
◦ telescopic imaging
◦ high speed radar
◦ the Stefan-Boltzmann law
◦ the Doppler principle
Question 2
If a yellow star is moving away from us very rapidly, what color will it appear to be?
◦ reddish orange
◦ greenish blue
◦ purple
◦ bluish purple