Tuesday, week 4 Arney on Systems and more Zita on Astrophysics in crisis Kuhn and Social constructionism This week – Library workshop #2 Next week - Research proposals (in teams) - midquarter conferences (seminar teams)

Arney on Systems Where is the Life we have lost in living? Where is the wisdom we have lost in knowledge? Where is the knowledge we have lost in information? The cycles of Heaven in twenty centuries Bring us farther from God and nearer to the Dust. T. S. Eliot, "Two Choruses from the Rock"

Kuhn on revolutions Original paradigm: good framework for solving old puzzles Anomalies: outstanding problems, inconsistencies? Crisis: proliferation of theories New paradigm: how can it replace the old?

Astrophysics in crisis Black holes: what have you heard? Big Bang: You’ve heard that “the laws of physics break down” in the earliest moment. Black holes can help us understand what that means.

Evidence for the Big Bang The 3-degree background radiation reveals the origin of structure in the universe

More evidence for the Big Bang Expansion of the universe: further galaxies are receding faster Amount of Hydrogen and Helium in the universe: beginning was very hot 3K radiation: universe has cooled to the present

Questions about the Big Bang What happened in the first tenth of a millionth of a billionth of a billionth of a billionth of a billionth of a second ( sec)? The universe was very small, so ask Quantum Mechanics. The universe was very massive and dense, so ask General Relativity (theory of gravity).

Current paradigms in physics Quantum Mechanics explains the very small General Relativity explains the very massive (theory of gravity)

How big was the universe in the beginning? R

General Relativity (gravity) The early universe was a singularity – like a black hole. Event horizon R = distance inside which everything is trapped BH R

Quantum Mechanics The early universe was very small – a point. Small quantum objects have an uncertain size or wavelength RR

Problem: the early singularity could be outside its own event horizon?! “Laws of physics break down” R RR

We need a new theory of “quantum gravity” String theory? Loop quantum gravity? Will one of these resolve the crisis and become our new paradigm? GUT?

Outstanding cosmological questions What physics operated before the Planck time? What is gravity? Higgs? Graviton? Other? What is dark matter? Neutrino mass? Wimps? What is dark energy? Why does universe’s expansion accelerate? How to unite gravity with QM? Loop quantum gravity? Superstrings? D-branes? Supersymmetric particles?

How to choose which model? Criteria: * New model answers old Q * Predictions pass tests * New puzzles solvable * Simplicity, beauty * More? My generation articulated this problem. Your generation will solve it.

Can science discover truth? Facts are “theory-laden”? Theories are created by humans and reflect their biases, language, culture…? In what sense can science be objective, if it is socially constructed? Stay tuned…

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