Question

Suppose that the entire Universe began to contract (collapse) right now. Five billion years from now, an astronomer looking at the spectra of galaxies. What would be the changes noted?

A. Spectral lines from planets and stars in the Milky Way would be all blue shifted.
B. Spectral lines from galaxies within a distance of less about 5 billion light years would be red shifted.
C. Spectral lines from galaxies farther than 5 billion light years would be blue shifted.
D. Spectral lines from galaxies within a distance of less about 5 billion light years would be blue shifted

Answer 1

spectral lines from galaxies within a distance of less about 5 billion light years would be blue shifted ( D )

Step-by-step explanation:

The spectral lines from planets and stars in the milky way would not be all blue shifted because the speed of light in the universe is extremely fast while the spectral lines from galaxies within a distance of less than 5 billion light years would not be red shifted due to the distance instead they would be blue shifted when viewed by an astronomer in the spectra of galaxies.

but spectral lines from galaxies farther than 5 billion light years would be red shifted instead of blue shifted as stated in the question.

Answer 2

D is correct.

Step-by-step explanation:

The contraction towards us will cause a blue shift, and after 5 billion years that blue shift light will finally reach us.