The story in cosmology seems to have become: we didn't believe in Lambda, then the Type Ia SN results were announced, then we did. #LCDMhi
The actual history was, of course, rather more involved. There were many observational indications of Lambda that paved the way. #LCDMhi
Prehistory: CDM and Inflation were both established in the 1980s. Standard CDM (SCDM) had Omega_m = 1.000 and H0 = 50. #LCDMhi
SCDM was Known, Khaleesi. Om < 1 was inconceivable. H0 > 50 was unfashionable. Lambda was Right Out. Unmentionable. #LCDMhi
The first time I personally heard Lambda mentioned as a serious scientific possibility was by Yoshii at a conference in 1993. #LCDMhi
Yoshii made a simple argument based on the N(m) test. There were so many faint galaxies, we needed a big volume - hence Lambda. #LCDMhi
Yoshii was shouted down. NO! Galaxies evolve! We don't need no stinking Lambda! #LCDMhi
In retrospect, http://bit.ly/1iJ1xF9 looks like a good detection of Lambda. Perhaps Yoshii & Peterson also deserve a Nobel prize? #LCDMhi
Indeed, there were many hints that Lambda was needed, e.g., http://bit.ly/1iAMdeE http://bit.ly/1hT7KO2 http://bit.ly/1pPdDkT etc. #LCDMhi
Certainly by the mid-90s it was clear that we were not going to make it to Om = 1. Inflation was threatened. SCDM was in crisis. #LCDMhi
A very influential 1995 paper http://bit.ly/1memdrT by Ostriker & Steinhardt did a lot to launch the concordance cosmology. #LCDMhi
I was very impressed by the breadth of data O&S discussed, all of which demanded low Om. I thought the case for Lambda less strong. #LCDMhi
The closing line of O&S still resonates today: "how can we explain the non-zero value of the cosmological constant" theoretically? #LCDMhi
O&S scrupulously avoided mentioning an important prediction of Lambda: the expansion rate of the universe should accelerate! #LCDMhi
So I wrote a brief note http://bit.ly/1rPs46d pointing out the predicted accelerated expansion. #LCDMhi
This was an early mention of accelerated expansion. But I meant it in a bad way: how crazy would that be?! #LCDMhi
I mean[t], surely we could live with Om < 1 but no Lambda. Can't we all just get along? #LCDMhi
Not really, as it turned out. I remember Mike Turner pushing the SN people very hard in Aspen in 1997 to Admit Lambda. Not.Yet. #LCDMhi
A year later, there were many more SNIa. Enough to see Lambda. This time, we were intellectually prepared to see it - unlike 1993. #LCDMhi
The rest, as they say, is history. There are still open fundamental issues. http://bit.ly/Sbnkf3 If we're ready to face them. #LCDMhi