As a humble scientist Lemaître didn't take the credit of the discovery of the expanding universe. Appearently there was a nice presentation by experimental part

As a humble scientist Lemaître didn't take the credit of the discovery of the expanding universe. Appearently there was a nice presentation by experimental particle astrophysicist Ariel Goobar at "Symposium - Georges Lemaître’s Big Bang In Modern Cosmology: A Celebration" last month: https://fys.kuleuven.be/ster/meetings/lemaitre/programme https://fys.kuleuven.be/ster/meetings/lemaitre/programme At the end it states: "SNIa cosmology provides stunning confirmation of cosmic expansion – as predicted by Lemaitre in 1927! •  Expansion currently accelerating – as proposed early on by Lemaitre to explain the age of the Universe •  Is it Einstein’s CC or some exotic new phenomena? Observers busy trying to find out. Theory badly needed!" Perhaps the dark energy is the combined weight of all those unproven undiscovered astral dimensions :-) Or perhaps it's something more mundane as unproven strings or quintessence: http://blogs.scientificamerican.com/critical-opalescence/2012/06/11/is-dark-matter-a-glimpse-of-a-deeper-level-of-reality/ http://blogs.scientificamerican.com/critical-opalescence/201... http://www.newscientist.com/article/dn12261-is-dark-energy-lurking-in-hidden-spatial-dimensions.html http://www.newscientist.com/article/dn12261-is-dark-energy-l... http://en.wikipedia.org/wiki/Quintessence_(physics) http://en.wikipedia.org/wiki/Quintessence_(physics)