What Hubble really saw

• Edwin Hubble studied “the realm of the nebulae” – fuzzy blobs – to try to figure out if they were in our galaxy or not

• He discovered individual stars which varied periodically in brightness

• Some of these stars were in our own galaxy, and he could use parallax to figure out how far away they were

• But others seemed to be much farther away, and they were also redshifted