In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this?

By observing individual Cepheid variable stars in Andromeda and applying the period-luminosity relation

Explanation:

In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. He was able to prove this BY OBSERVING INDIVIDUAL CEPHEID VARIABLE STARS IN ANDROMEDA AND APPLYING THE PERIOD-LUMINOSITY RELATION

the last day of school because i didn’t have to go to school the next day