# From CMB anisotropy data observed in 1992, did astronomers figure out that the universe should be accelerating before its discovery in 1998?

CMB anisotropy was measured in 1992. I assume that astronomers, then, like now, would have been able to deduce the cosmological constant and things like that from the CMB anisotropy data. Then, from the cosmological constant and things like that, they would have been able to find that the current universe was accelerating. Did they indeed know that the current universe should be accelerating before its observation in 1998? Or, was the discovery in 1998 a great surprise? What was the exact situation between 1992 and 1998?

• I would wait a bit before accepting the first answer within minutes of it appearing. You discourage others from answering and it may also be that other want to dispute my answer or point out inaccuracies/suggest improvements. – Rob Jeffries Nov 14 '18 at 14:49
• The discovery was not a complete surprise, because there was some non-CMB evidence for inconsistencies in the 1990s. E.g., the current, local expansion rate of the universe as deduced from the Hubble constant implied a universe that seemed a little too young for the oldest stars. – Peter Erwin Nov 15 '18 at 8:03
• Admittedly, the indirect evidence for acceleration was weak, since both the Hubble constant and the ages of stars were rather uncertain, – Peter Erwin Nov 15 '18 at 8:04

In actual fact, the evidence for $$\Lambda$$ from the CMB alone is rather weak. As explained in one of Wayne Hu's cosmology tutorials, the strongest evidence from the CMB is that the total density of the universe $$\Omega = 1$$ from the CMB and this can then be combined with other data (e.g. primordial abundances of D, He; galaxy cluster dynamics; gravitational lensing) to suggest that the matter contribution to this is only $$\simeq 0.3$$.