Who stated the universe is expanding?

Answer 1

The Doppler effect is well known, and Fizeau observed the red-shift of the light from distant stars. So the effect was called Doppler-Fizeau.

There are a class of astronomic objects called the Cepheid Variables in which it is observed that the rate of variation in the brightness of the star related to its absolute brightness, and therefore its mass. Thus these stars can be used as a measure of distance, as the period of their variability does not change with distance, but their apparent brightness and their red-shift does.

Hubble made a number of observations of Cepheids in the Andromeda galaxy. The article on Cepheid Variables in wikipedia.org is well worth reading, as it illustrates scientific discovery and enquiry. He went on to reason that the Cepheids could be used as a standard measure of astronomical distance. And this formed the basis of the Expanding Universe.

These observations are one of the foundations of cosmology.