Lecture 5  Finish Part 1 of The Elegant Universe  Review for test 1

The Elegant Universe  Turns out there are 4, rather than 2, fundamental forces and that gravity is the weakest, particularly at the level of the sub-atomic.  Determinism seems to hold in terms of large objects (us, earthly events, galaxies, and stars): there are law-like relationships between causes and effects, and events are predictable on their basis.  This is the nature of the universe that Einstein, Newton, and generations of physicists believed in and sought to understand.

The Elegant Universe  But in the 1930’s, physicists such Neils Bohr were studying the realm of the very small: the world of atoms and subatomic particles and finding fundamentally different from the macroscopic realm in terms of cause/effect relationships and, most importantly, in terms of determinism.  It is indeterminacy – chance – they argued that is the norm in the subatomic realm. It is far less regular, far less predictable, and far less familiar than the determinism that seems to hold at the level of large objects.

The Elegant Universe  Quantum theory (or quantum mechanics) the study of quanta (plural of ‘quantum’) – discrete, indivisible units of energy – emerged and many of its predictions were confirmed to an impressive degree.  Einstein hated indeterminacy (stating, famously, that “God doesn’t play dice”) and was, more or less, left behind as the new forces and phenomena at the quantum level became increasingly the subject of research.  Among the implications of experiments in Quantum theory: you cannot determine both the position and the velocity of a quantum at the same time  Observing events involving quanta changes what occurs.

The Elegant Universe  Major themes:  Unification: a theory of everything as the holy grail of physics  Reasons to think it is plausible: past unifications, metaphysical assumptions about the universe  Simplicity! Elegance!  The laws of physics apply everywhere at all times  Testability (related to verifiability and falsifiability)  The (at least apparent) impossibility of ever observing strings.

Review  Evidence: what is it like for theories in physics and biology that posit objects or events we cannot directly observe?  What kinds of argument do scientists who posit objects or events we cannot directly observe offer in support of positing such objects/in support of such theories?  What kinds of philosophical assumptions underlie scientific research: fallibilism/epistemological, universality or contingency, simplicity/elegance or jury rigging, metaphysical, aesthetic motivate and/or inform scientific research?

Review  Case studies  Particle physics  Evolutionary Theory  Human evolution  String Theory  The Copernican Revolution  The Darwinian Revolution  Ancient Greeks of Miletus and Democritus  Vegetation Myths

Review  Forms of reasoning  Thought experiments  From data to hypothesis  Reverse engineering  Inference to the best explanation  The Likelihood Principle  Modus Tollens  Modus Ponens  Affirming the consequent  Denying the antecedent

Review  People and their arguments  Lederman, Thales, Anaximander, Anaximenes, Democritus  Paley, Darwin, and Gould  Copernicus, Galileo, and their critics  Brian Greene, Einstein, Glashow, String Theorists  Glashow’s credo