The @NobelPrize to Jim Peebles represents, among other things, the first Nobel prize for the discovery of Dark Matter. Here are some thoughts, also based on discussions with him about the evidence for DM, and his own role in the discovery. THREAD 
First, to clear any confusion: the observational discovery of the accelerated expansion of the universe (often referred to as the Dark Energy problem) had already celebrated with the prize awarded in 2011 nobelprize.org/prizes/physics…
But until today no prize had been awarded for the discovery of DM, despite many pioneers had been put forward as candidates: Bosma, Roberts, Rubin, etc. (I hope they will be recognized eventually, although it is unfortunately too late for Vera Rubin, who passed away 3 yrs ago)
Peebles played a key role in establishing the existence of an unseen matter component of the Universe in the 1970s, by bringing together evidence in galaxies, clusters and on cosmological scales. adsabs.harvard.edu/abs/1974ApJ...…
Then, most importantly, in the 1980s he showed that DM had to be *fundamentally different* from ordinary matter. When I asked Peebles what convinced him that DM exists, he said that he "became convinced ... by the increasingly tight bounds on the CMB anisotropy”
In other words, he figured that to grow galaxies from a universe that was hot and homogeneous right after the Big Bang, we needed a form of matter that interacts with gravity but does not behave like atoms
Subsequent work confirmed — actually to his own surprise — his theory. Anisotropies in the CMB were eventually found (Nobel prize 2006), and evidence for a “mostly dark” universe became ever stronger.
More information about the history of dark matter here: arxiv.org/abs/1605.04909 (with Dan Hooper @DanHooperAstro) and here arxiv.org/abs/1703.00013 (with J. de Swart @JGdeSwart and J. van Dongen).
Another prize awaits those who will identify *the nature* of dark matter. Here’s an incomplete list of present/upcoming experiments worth following: @ATLASexperiment @CMSExperiment @Xenon1T @lzdarkmatter @DarwinObserv @CTA_Observatory @AMS_02 @LSST @EC_Euclid @LISACommunity
