Explain how redshift leads to the idea that the Universe is expanding.
Stars in a distant galaxy emit radiation. The total luminosity of the stars in the galaxy is 
. The emission spectrum of the radiation contains a line X at a wavelength of 
. Radiation from the galaxy is observed on the Earth. The observed radiation has a radiant flux intensity of 
. In the observed emission spectrum, line X is at a wavelength
of 
. Determine:
the distance 
of the galaxy from the Earth
the speed 
of the galaxy relative to the Earth.
.
.
