That’s So Second Millennium
Episode 050 - Craig Lent: decoherence, entropy, and faith

Episode 050 - Craig Lent: decoherence, entropy, and faith

March 11, 2019

0:00 - Three issues: entropy, decoherence, Schrodinger vs. Dirac equations

2:30 - Schrodinger uses a non-relativistic Hamiltonian, with a p^2/2m kinetic energy

3:00 - Dirac equation absorbs special relativity by shifting from scalar to spinor field

4:00 - Quantum field theory as a further extension, accommodating fields that include many particles

5:00 - Field Lagrangian and all the particles and interactions in the Standard Model

6:00 - Even "everyday" gravity is in some sense accommodatable in the theory, just not extreme gravity capable of "separating out the vacuum"

8:00 - Decoherence, not to be confused with the measurement problem

9:00 - Decoherence arising from the interaction of a simple system with other systems

10:00 - Reduced density matrix begins to look classical

11:00 - Zurek and the work on decoherence: states that are "chosen" to survive interaction with the environment

11:30 - Measurement problem not solved by this work

12:30 - Entropy: the proposal that entropy is most fundamentally lack of information

progress from the special case of thermodynamic entropy, to statistical mechanics,

to von Neumann's quantum definition, to Shannon's information theory

21:00 - Craig's career: why is an engineer so interested in the fundamentals of physics?

24:00 - Journey of faith

30:30 - People of Praise in Indianapolis

31:20 - Final thoughts

Episode 049 - Craig Lent: physics and humanity

Episode 049 - Craig Lent: physics and humanity

March 4, 2019

0:00 - Introduction

1:00 - The power of physicalism/reductionism: a tremendously powerful method

2:00 - Course on physicalism and Catholicism; Sean Carroll's least hysterical "poetic naturalism"

3:00 - The lack of evidence for "emergence" in the sense of "downward causation"

3:30 - Soft and hard emergence

10:15 - Materialism vs. physicalism and reductionism: philosophical materialism

13:00 - Are human beings exhausted by this account of reality?

14:00 - The break with the mechanical universe of 19th century physics underappreciated

15:00 - Laplace's demon

16:30 - Thermodynamics

17:30 - Future not contained in the present

19:00 - Einstein & hidden variables

20:00 - Bell inequality experiments

24:00 - Entanglement

26:00 - Human experience: both, as physical, but also as having choices

27:00 - Quantum physics on many body systems

28:00 - The hard problem of consciousness

29:00 - The explanatory gap

31:00 - The tendency to explain the brain as "just like" some recent piece of technology

33:00 - Complexity of neurons, the continuing relevance of physical laws amid the complexity

35:00 - Continuing relevance of quantum effects at the level of neurotransmitter molecules, etc.

36:00 - Quantum effects in weather and rock mechanics

Episode 036 - Anne Hofmeister on Galactic Rotation, Math, and Glass

Episode 036 - Anne Hofmeister on Galactic Rotation, Math, and Glass

December 3, 2018

The times below are continuations from the last episode. My opening is about 1:30, and then we start with galaxy motions at "26:00".

26:00 Galaxy motions

27:00 Galaxy rotation curves: do not match Keplerian orbits

28:00 Galaxies spin more like records (laggy soft records); mass distribution is nothing like the Solar System

29:00 Hurricanes as a better analogy for galaxies

30:00 Stars in a galaxy move in local organization

32:00 Nebulas

34:00 The opposite extreme: rigid body rotation

35:00 Gravitational attraction between stars creating coherence

36:00 Curiosity that gravity and electrical forces are both inverse square laws

37:00 Poisson's equation

38:00 Summing densities in Poisson's inhomogeneous term is physically meaningless; intensive quantities can't be summed that way

40:00 Gauss' theorem: flux through a surface and quantity within a volume

41:00 Summing is for extensive variables

42:00 Pressure an ambiguous variable

43:00 Future work

44:00 Thermal expansivity: Giauque

45:00 Problems with the glass transition measurements done in the past: need to completely drive out water from the experimental charges

48:00 Wrapup

Episode 035 - Anne Hofmeister Shakes Up Earth Science

Episode 035 - Anne Hofmeister Shakes Up Earth Science

November 26, 2018

TSSM goes heavy: hard-hitting journalism from one of science's great controversialists, Anne Hofmeister. Intrigued? Disagree? Write me an email ( or look her up at Washington University in St. Louis' EPS department website.

The times below are keyed to the start of the interview and ignore my opening (just over 2 min).

0:00 Introduction

1:00 Anne's background (sorry, this part Anne was talking so quietly that I can't seem to fix it with Audacity, but bear with us; we moved the microphone and figured some things out and it gets better)

2:00 Spectroscopy and heat transfer

3:00 Thermal conductivity experiments and their pitfalls

5:00 Criticism of the history of thermodynamics and heat transfer; identification of light and heat

6:00 Problems with equilibrium and elastic collisions in theories of thermodynamics

8:00 Criticism of phonon theory

10:00 Electron and vibrational transfer of heat decoupled; metals and heat transfer

13:00 Garnet

14:00 Earth's interior: convection, the Rayleigh number

15:00 Viscosity

16:00 The Earth's mantle: nearly all solid

17:00 Plate tectonics without mantle convection

18:00 An even more radical idea: heat is being trapped inside the solid Earth

19:00 [there was a distortion I had to cut]

20:00 Implications: heat generation is in the crust (this part is widely known!)

21:00 Implications: the core is melting, not solidifying?

22:00 The geodynamo and magnetic field

23:00 The core: buffered at the temperature of melting high pressure iron

24:00 Magnetic modes diagram for the planets: spin and magnetic field