How did Edwin Hubble discover the cosmos was expanding?

Edwin Powell Hubble was born in Missouri in 1889, the son of an insurance executive, and the family moved to Chicago nine years later. ... Despite a suggestion first made by William Herschel more than a century earlier, the accepted view was that all nebulae were relatively nearby patches of dust and gas in the sky. read more

If we assume that H 0 provides us with a value for the current rate of expansion then its inverse, that is 1/H 0 tells us the Hubble time which is a measure of the age of a universe expanding at a constant rate. Hubble calculated a value for H 0 of about 500 km. s-1. Mpc-1. (1 Mpc-1 is 1 megaparsec or about 3.26 million light years. read more

In 1929 Hubble published a paper that would lead to the realization that the universe was expanding. As astronomers’ abilities to measure the distance and Doppler shift of galaxies improved over the years, Hubble’s and Humason’s discovery of the expanding universe was confirmed. read more

It’s because Hubble’s work was pivotal in changing our cosmology: our idea of the universe as a whole. read more