I think that the discovery that the universe is expanding was one of the most significant in science. It is on a similar level with Darwin's discovery of the law of evolution. It tells us the universe wasn't always the way it is today. It tells us we came from something, something violent, something extraordinary.The show credited Hubble with the discovery. I mentioned last month that Lemaitre was cheated by a translator. Now a new paper (and forthcoming book) answers Who discovered the expanding universe?.The answer is Lemaitre, as I also explain in my book. Most of the books credit Hubble instead. (Brian Greene's recent book on multiple universes is an exception.) It appears that the mainstream physicists do not want to credit a Caltholic priest.
Another new paper, provocatively titled Is the Universe really expanding?, also credits Hubble and says:
Hubble initially interpreted his redshifts as a Doppler effect, due to the motion of the galaxies as they receded for our location in the Universe. He called it a ‘Doppler effect’ as though the galaxies were moving ‘through space’; that is how some astronomers initially perceived it. This is different to what has now become accepted but observations alone could not distinguish between the two concepts. Later in his life Hubble [Hubble 1947] varied from his initial interpretation and said that the Hubble law was due to a hitherto undiscovered mechanism, but not due to expansion of space -– now called cosmological expansion.This suggests that not only was Hubble after Lemaitre, but he did not have the concept that the universe itself was expanding, as Lemaitre did, and as the textbooks say so. Furthermore, Hubble did not accept the expansion of the universe 20 year later.
Update: Another new paper addresses Lemaitre's priority. A.D. Chernin says, "In 1927, Lemaitre discovered dark energy and Hubble confirmed this in 1929." He also says:
A non-traditional point was however made by Steven Weinberg in "The First Three Minutes": "Actually, a look at Hubble’s data leaves me perplexed how he could reach such a conclusion – galactic velocities seem almost uncorrelated. In fact, we would not expect any neat relation of proportionality between velocity and distance for these 18 galaxies – they are all much too close, none been further than the Virgo Cluster. It is difficult to avoid the conclusion that... Hubble knew the answer he wanted to get."He probably got wind of Lemaitre's work.