Thursday, March 15, 2018

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:


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:

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. Our subreddit.

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