1. 8 ii 2012KIPAC1 The Hubble Constant Current and Future Challenges Roger Blandford KIPAC

2. Topics Why do we care? How are we doing? How many (Hubble) flowers? Physics vs magic? Validation? What next? 8 ii 2012KIPAC2

3. 8 ii 2012KIPAC3 Why do we care? Serious questions require independent Ho –Is the world flat? –Neutrinos, neutralinos, neutonian gravity Major discoveries still possible –New components of universe?

4. 8 ii 2012KIPAC4 How are we doing? Amazingly well! –Hard work Convergence real? – We could all be measuring the same thing accurately!!

5. 8 ii 2012KIPAC5 How many (Hubble) flowers? Continue all approaches as of now –Surprising conclusion Expect some efforts to cease to be viable –TACs, students, postdocs… will cease to be interested –Future Observations Eg Planck, weak lensing, BAO, SN… –Future Experiments Eg LHC neutrinos direct. Indirect dark matter detection –Future Telescopes Eg BigBoss…

6. Physics vs magic CMB, SZ, BAO, reconstruction… –Well understood SNIa, Masers… –Poorly understood Lenses, TRGB, Populations, Cepheids… –Intermediate Astrophysics –Galaxy structure, gas dynamics Understanding physics –Enhances credibility –better control of systematics 8 ii 2012KIPAC6

7. 8 ii 2012KIPAC7 Validation? Scientific integrity –High moral character of astronomers! –Errors in answers to important questions quickly exposed –Choose between being castigated as a fool or a knave Need a protocal for deciding when to announce/publish –Analog of “five sigma” Blind leading the blind? –Open boxes, distance challenges Particle physicists vs astronomers –galaxies are like fundamental particles Frequentist statistics –galaxies are like people (though not as easily classified!) Bayesians – priors and evidence Quality vs quantity –e.g. clusters/lenses vs SNIa/Cepheids –Picking cherries or making do with lemons?

8. What next? Communique –Red(shift) brigade? Second meeting? –2-3 yr? Thanks –Sherry, Stefan, Martha… 8 ii 2012KIPAC8