One of the most important observations in the history of astronomy was the one by Edwin Hubble that established that there are other galaxies, quite removed from the Milky Way. How did Hubble show this?
A) by debating with Harlow Shapley and being more eloquent
B) by observing a supernova explosion in a nearby galaxy, using it as a "standard bulb"
C) by observing a Cepheid variable in a nearby galaxy and using it to get the distance
D) by measuring the distances to many globular clusters using parallax
E) by going to see Einstein, who knew the answers to these kinds of questions

Question

Quizplus · Accepted Answer

Hubble observed a Cepheid variable in a nearby galaxy (the Andromeda Galaxy) and used it to determine its distance, which showed that it was far beyond the Milky Way and therefore other galaxies existed. This was the first evidence for the existence of the universe beyond the Milky Way.

One of the Most Important Observations in the History of Astronomy