Fifty Years of CMB Anisotropy Experiments (and Theory)

….in 15 Minutes

Bruce PartridgeHaverford College

bpartrid@haverford.edu

A Brief History in 6 epochs

Epoch 1 -- 1965 to ~1970Isotropy as one test of the cosmic origin of the CMBFlavor: “Are we right?”Spectrum: Roll and Wilkinson find To = 3 K (and Dave later finds

evidence for turn-over at spectral peak, confirmed by Boynton et al)

A Brief History in 6 epochs

Epoch 1 -- 1965 to ~1970Isotropy as the other test of the cosmic origin of the CMBFlavor: “Are we right?”Isotropy: by 1967, established ΔT/T < 0.002

A Brief History in 6 epochs

Epoch 2 – 1970 -1977The epoch of upper limitsUsing available equipment and facilitiesFlavor: “What can we do with what we have?”

Hunt for the dipole: definitive results by 1977 (the U2 expt.)But earlier strong hint(Conklin and Bracewell,1971)

Limitations: range of angular scale; atmosphere; detector sensitivity

A Brief History in 6 Epochs

Epoch 3 -- 1977 to 1992Retrenchment Purposeful experimental design Well-grounded theoretical results (But too little interaction between the two)Flavor: “How can we do this better?”

Culmination in 1992: COBE DMR detection of statistical evidence for ΔT/T ~ 10-4

Limitations: range of angular scale; foregrounds made blatantly visible, but not yet limiting

A Brief History in 6 EpochsEpoch 4 -- 1992-2003CMB anisotropy science maturesTheory influences experimental designThe power spectrum as THE representation of anisotropiesSearch for and detection of first acoustic peakEvidence for Silk damping in the high-ell tail

Flavor: “We’re doing the experiments right; now to beat the systematics and foregrounds…”

Limitations: foregrounds; sensitivity of single detectors; instrumental systematics

Culmination: the 2003 WMAP power spectrum

From Lyman Page’s summary in Finding the Big Bang

Culmination of Epoch 4: the 2003 WMAP Power Spectrum

(Actually the five year results)Figure from Dunkleyet al. 2009 toshow thatdamping tail requiresother results

A Brief History in 6 EpochsEpoch 5 – 2003 – 2015 (WMAP to Planck)New directionsNew infusion of innovation/cleverness from theoristsFlavor: “How can we wring more cosmological and physical results out of the data?”

Polarization (EE first detected by DASI, 2001)The richness of the damping tail (the province of SPT and ACT)Exploiting the CMB for physics as well as cosmology

Limitations: now clearly foregrounds; use of arrays gets around limits on sensitivity of individual detectors (makes focal plane and optics harder); instrumental systematics

A Brief History in 6 Epochs

Epoch 6 – the FutureA few observations:EE and TE polarization will be firmly nailed downBB depends on which model of Inflation (a good thing) – and on

control of foregrounds (a hard thing)The CMB will increasingly ne used as a background for

gravitational lensingTheorists will find new ways to use the observations

Some Thanks

To the organisersTo George Field for teaching me cosmology (1961)To Bob Dicke (a) for hiring me (1965) and (b) for asking so many

fundamental AND answerable questions (always)To Dave Wilkinson for teaching me how to care about

experimentsTo Jim Peebles for teaching me how to care about scientific

writingTo so many (some here) – Martin Rees, Rod Davies, Rashid

Sunyaev, Bernard Sadoulet, Paul Richards, Reno Mandolesi, Jean-Loup Puget, for teaching me that science also flourishes in foreign lands, including California

To the young folks who will keep CMB science thriving