Question

1. which of the following describes the appearance of galaxies decreasing in spectral wavelength as they move away from the milky way? blueshift green flash purple sky redshift

Explanation:

When galaxies move away from the Milky - Way, their spectral wavelength increases, which is called redshift. Blueshift occurs when an object is moving towards the observer. Green flash and purple sky are not related to the change in spectral wavelength of galaxies moving away.

Answer:

redshift