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
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!"
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/201... http://www.newscientist.com/article/dn12261-is-dark-energy-l... http://en.wikipedia.org/wiki/Quintessence_(physics)