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Physics Frontiers

Jim Rantschler and Randy Morrison discuss physics from elementary particles to cosmological effects at the limits of our theoretical knowledge or have recently emerged.

Weekly hand curated podcast episodes for learning

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Dark Energy

Randy helps Jim get a handle on Dark Energy. Why do we need it? What could it be? What does it have to do with you? How close are we to knowing anything about it?Show Notes: http://frontiers.physicsfm.com/23

45mins

9 Feb 2018

Rank #1

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A Gravitational Arrow of Time

Jim and Randy discuss a cosmological theory that purports to find an explanation for the arrow of time in gravitational theory based on the shape and distribution of matter and how it evolves. Show notes: http://frontiers.physicsfm.com/12

41mins

20 Aug 2017

Rank #2

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Gravitoelectromagnetism

Randy talks to Jim about gravitoelectromagnetism. Based on the similarity between Newtonian gravity and electrostatics, there should be a second gravitational field,the gravitomagnetic field. What are the implications of the existence of such a field, and how large are those effects? Show notes: http://frontiers.physicsfm.com/3

41mins

6 Dec 2016

Rank #3

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Spooky Action at a Distance

Jim and Randy discuss experiments that put a minimum superluminal speed of communication between parts of a wavefunction.Show Notes: http://frontiers.physicsfm.com/44

47mins

16 Jul 2019

Rank #4

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Loop Quantum Gravity

Jim and Randy discuss loop quantum gravity, and integration of quantum mechanics and gravity that quantizes space-time itself through the use of uncertain quanta of volumes and the random connections between them.

44mins

16 Aug 2019

Rank #5

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The Physics of Time Travel

Randy and Jim talk about traveling through through time, discussing relativity and, in particular, Kurt Goedel's solution for closed timelike curves in General Relativity. Show notes: http://frontiers.physicsfm.com/17

43mins

24 Nov 2017

Rank #6

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The Dimensionality of Space-Time

Jim discusses why the world we observe is 4-dimensional with Randy. We discuss anthropic and fundamental reasons why we need 3 dimensions and no more than one time dimension for reasons of complexity, predictability and stability.Show Notes: http://frontiers.physicsfm.com/38

43mins

25 Nov 2018

Rank #7

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Bimetric Gravity

Randy introduces Jim to Sabine Hossenfelder's bimetric theory of gravity. In this gravitational theory, there are two types of matter whose only interaction is through gravitation. However, each one reacts to space-time differently, resulting in different metric tensors for each. In low-curvature situations, this creates a kind of anti-gravitation.Show Notes: http://frontiers.physicsfm.com/47

46mins

24 Nov 2019

Rank #8

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Post-Newtonian Gravitation

Jim discusses the Parameterized Post-Newtonian formalism with Randy. The PPN framework is a general, linearized metric theory of gravity that can simulate all metric theories of gravity and compare them to solar system sized experiments.Show Notes: http://frontiers.physicsfm.com/31

41mins

8 Jun 2018

Rank #9

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Tunneling Time

Jim talks to Randy about the amount of time it takes for an electron to tunnel through a forbidden region of space. Astoundingly, how quickly this happens has been a subject of debate for eighty years and is still unresolved.Show Notes: http://frontiers.physicsfm.com/32

47mins

7 Jul 2018

Rank #10

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Retrocausality

Jim and Randy look at how quantum mechanics is affected by time. Most importantly, what happens when temporal boundary conditions are used to create standing waves in the wave function of a particle?Show Notes: http://frontiers.physicsfm.com/33

34mins

25 Jul 2018

Rank #11

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The Gravitational Equivalence Principles

Jim talks to Randy about the different ways in which the equivalence principle of general relativity can be formulated. More than just the equivalence of accelerations, the different possible meanings of the equivalence principle mean different things about how gravity works. From weak to strong, from Einstein's equivalence principle to Schiff's conjecture, the implications of these theories are explored.Show Notes: http://frontiers.physicsfm.com/27

46mins

15 Apr 2018

Rank #12

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The Origin of Inertia

Randy tells Jim about a scheme that uses Mach's Principle - the idea that there is a preferred background frame with respect to the fixed stars - to explain the origin of inertia.Show Notes: http://frontiers.physicsfm.com/21

38mins

11 Jan 2018

Rank #13

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X17

Jim and Randy discuss a possible "fifth force," the hypothetical X17 particle that has been seen in several experiments. Erratum: The g-2 of the muon was shown to be off by 1 part in 500,000 in 2001 at Brookhaven. It may not be in there, I'm not sure how much of that I cut out.Show Notes: http://frontiers.physicsfm.com/50

38mins

3 May 2020

Rank #14

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The Consistent Histories Interpretation of Quantum Mechanics

Jim and Randy discuss the consistent histories interpretation of quantum mechanics. The brainchild of Robert Griffiths and with a surprisingly strong set of supporters, Consistent Histories seems to be a strong, logical description of what happens in the quantum world.Show Notes: http://frontiers.physicsfm.com/30

45mins

24 May 2018

Rank #15

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Photonic Molecules and Optical Circuits

Randy tells Jim about photonic molecules, pairs of photons that create bound states like molecules do through a force mediated through an ultracold gas and similar ideas in optical circuits. They also discuss application of the same for quantum computing. Show notes: http://frontiers.physicsfm.com/11

36mins

16 Jul 2017

Rank #16

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General Relativity for the Experimentalist

Randy shares some of his favorite papers with Jim: papers on general relativity by engineer and science fiction author Robert L. Forward on how general relativity could be used in a terrestrial environment, including proposals for devices and materials. These papers are "General Relativity for the Experimentalist" and "Guidelines to Antigravity." Show notes: http://frontiers.physicsfm.com/6

49mins

14 Feb 2017

Rank #17

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Time Crystals

Jim talks to Randy about structures that are periodic in time like crystals are periodic in space. Show notes: http://frontiers.physicsfm.com/20

34mins

22 Dec 2017

Rank #18

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Wigner's Friend

Randy and Jim discuss experiments that purport to show that there is no such thing as objective reality.Show Notes: http://frontiers.physicsfm.com/46

44mins

22 Sep 2019

Rank #19

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f(R) Theories of Gravity

Jim and Randy discuss gravitational theories that modify general relativity by changing the action using a polynomial dependence on the Ricci scalar. Although not physically motivated, some of these theories produce effects similar to those of dark matter, dark energy, and cosmological constants. Show notes: http://frontiers.physicsfm.com/9

37mins

2 Jun 2017

Rank #20