The Big Questions in 2020? Mario Livio Space Telescope Science Institute

2 The Dangers of Predicting the Future of Science and Technology London in 1900 had 11,000 horse-powered cabs and several thousand buses, each requiring 12 horses per day. An average horse produces pounds of manure per day. One might have predicted that in 50 years every street in London would be buried under nine feet of manure!

3 Is There Extraterrestrial Intelligent Life? We could progress systematically: Find terrestrial planets… In habitable zones… Characterize their atmospheres… etc.

4 Is There Extraterrestrial Intelligent Life? Or… we could take shortcuts: Searching directly for signals of extraterrestrial intelligent civilizations (e.g. SETI).

5 The Nature of Dark Energy, Dark Matter

6 SNAP The Nature of Dark Energy Observations will place increasingly tighter constraints on “strength” (w) and “permanence” (w‘ ). Future observations will use supernovae, baryon acoustic oscillations, CMB, integrated Sachs-Wolfe effect, etc. ADEPT Destiny SPACE, DUNE

7 The Nature of Dark Matter (and Energy?) The Large Hadron Collider may find the Higgs (?), supersymmetric particles (?), extra dimensions (?). New large telescopes will yield information about dark matter distribution, large-scale structure.

8 The Nature of Dark Energy Additional tests of alternative theories of gravity (e.g. by lunar ranging experiments).

9 Direct Observational Evidence for Inflation? Possible detection of B-mode polarization power spectrum The gravity wave signature of inflation

10 The Physics Near Black Holes Could we detect directly the event horizon?

11 Ultimate Goal: Quantum Theory of Gravity Most of the time, gravity and quantum mechanics “live” in their separate worlds… But they inevitably meet in two places: Black Holes Big Bang Hubble Ultra Deep Field HST ACS

12 Are there Observational Signatures of String Theory? What physics selects the vacuum solution of our universe?

13 The Vision for Space Exploration will enable progress in many areas of Astrophysics Capabilities are ideally suited for transportation of large- aperture telescopes (or their components), of the type envisioned for a broad range of future astronomical missions. The VSE should be planned so as not to preclude — and to the extent possible to include — capabilities that will enable astrophysics from free space. Almost 10m diameter fairing Lifting power of tens of tons to Sun-Earth L2 Ares IAres V An Opportunity That Shouldn’t Be Missed

14 The Lunar Surface Can Be Used to Study The Epoch of Reionization and Beyond Reionization Fluctuations are about 10 mK z = 12.1, 11.1, 10.4, 9.8, 9.2, 8.7, 8.3, 7.9, 7.6 z = 12.1 z = 11.1z = 10.4 z = 9.8z = 9.2z = 8.7 z = 8.3z = 7.9z = 7.6 Time since the Big Bang (years) Time since the Big Bang (years) ~400,000 ~500 million ~1 billion ~9 billion ~13.7 billion Z ~ 1,000 Z ~ 10 Z ~ 6 Z ~ 0.5 Z = 0

15 Observations of redshifted 21 cm (in the frequency range MHz) neutral hydrogen emission could probe 7 ≲ z ≲ 100 (100 million - 1 billion years after the Big Bang) On Earth Far side of Moon offers: 1.Very little RFI 2.Avoids Earth’s ionospheric frequency cutoff (at ~10 MHz) 3.No ionospheric distortion at higher frequencies 4.No disturbances from weather and human activity. Far side of Moon offers: 1.Very little RFI 2.Avoids Earth’s ionospheric frequency cutoff (at ~10 MHz) 3.No ionospheric distortion at higher frequencies 4.No disturbances from weather and human activity. On the Moon “Everyone is a Moon, and has a dark side.” − Mark Twain

16 Relatively Easy to Do? Low frequency radio observations require only lightweight dipoles