Antimatter Production at a Potential Boundary

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Recorded: 6/17/2017 Released: 3/25/2017

Randy discusses a proposal for the production of antimatter without using supercolliders with Jim. This proposal would have used Klein's paradox for the production of electron-positron pairs at a very sharp, steep potential boundary produced through the Casimir effect.

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Notes:

1. The paper we read for this program:

• Lapointe, M., "Antimatter Production at a Potential Boundary." NASA/CR 2001-211116 (2001).

2. The NASA Institute for Advanced Concepts no longer exists (apparently it closed down in 2007), but there is now a NASA Innovative Advanced Concepts, a program with the same acronym that seems to have a similar purpose (if not, tell me the salient difference in the comments).

3. Our listenership has increased markedly since we recorded this episode last June. We had 1,057 downloads in the first fifteen days of June 2017, and in the first two weeks of March we had 3,117. In both cases there were no podcasts published during the time interval (in the current case because this is my heavy semester at work and it eats into my free time).

4. Please visit and comment on our subreddit, and if you can help us keep this going by contributing to our Patreon, we'd be grateful.

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Gravitational Field Propulsion

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Randy introduces Jim to several ways in which people have theorized that gravity can be used to propel an object through space. In order of likelihood and in inverse order of coolness:

• The Slingshot Effect -- Using a gravitational well to increase the energy available to an object. (In use)
• The Penrose Process -- Using a rotating black hole to gain energy. (Penrose)
• Negative Inertia Mass -- If mass has both a negative charge and inertia, then you can build a device that moves perpetually (RL Forward)
• Induced Gravitational Dipoles -- Spinning half of a sphere will (supposedly) propel it in some direction or other. (Jeong)
• The Alcubierre Drive -- A process that would sneak around the laws of relativity and allow someone to travel faster than light. (Alcubierre, White)

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Notes:

1. The papers we read for this program:

• Wisdom, J., "Swimming in Space-Time: Motion by Cyclic Changes in Body Shape." Science 299, 1865 (2003).
• Longo, M.J., "Swimming in Newtonian Space-time: Orbital Changes by Cyclic Changes in Body Shape." American Journal of Physics 72, 1312 (2004).
• Forward, R.L., "Negative Matter Propulsion." Journal of Propulsion and Power 6, 28 (1990).
• Forward, R.L., "Space Warps: A Review of One Form of Propulsionless Transport." Proceedings of the 25th Joint Propulsion Conference (1989).
• Jeong, E.J., "Anomalous Center of Mass Shift: Gravitational Dipole Moment." [arXiv]
• Alcubierre, M., "The Warp Drive: Hyper-Fast Travel Within General Relativity." Classical and Quantum Gravity 11, L73 (1994). [arXiv]
• White, H., "Warp Field Mechanics 101." DARPA/NASA 100 Year Starship Conference (2011).

2. The slingshot effect is in common use and is a topic viable at the junior mechanics level in such books as Taylor's and Morin's.

3. There is a problem defining the center of mass in general relativity, and we've recorded at least one podcast related to the topic (although not directly addressing it) between the recording of this last June and its publication in March. But the problem is with defining mass, not the center of mass. And because of the simplicity of the space-time swimmers, I'm still not sure its as much of a problem as some people do.

4. Popular articles for this program:

• Gueron, Eduardo, "Adventures in Curved Spacetime." Scientific American 301(2), 38 (Aug 2009)

5. The video Randy keeps talking about in the podcast he found linking through The Hammock Physicist Blog of Johannes Koelman. You can download it here from the IOP. I haven't yet found the article IOP attached it to.

6. I'll make a video of the non-commutative motion diagrams that I sent Randy and put a link up here.

7. Please visit and comment on our subreddit, and if you can help us keep this going by contributing to our Patreon, we'd be grateful.
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