In the 1920s came the development of both the theory (from Einstein’s general relativity theory) and the observations that (apparently) meant that the Universe is expanding. Edwin Hubble made observations of nearby galaxies and he interpreted those observations to mean that they were rapidly receding from our point in space. That discovery seemed to settle two big questions of that time: Is our Galaxy all there is? And, Is the Universe static or expanding?
Later in another blog I will discuss more on Hubble’s observations and his interpretation. Previously, I discussed the issue of static or expanding in regards to the Universe.