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Worldbuilding

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  • $\begingroup$ The heck do you mean by light cone? $\endgroup$ Commented Dec 20, 2015 at 21:42
  • $\begingroup$ I expect it means the speed of light. I.e. if he goes back one second he can see everything within 1 light second of him. Which is already 186 thousand miles....so basically he can see anywhere on earth. $\endgroup$ Commented Dec 20, 2015 at 21:54
  • $\begingroup$ @TimB: Exactly. On earth it's not really a limitation, but he can't for example look at a star (whose light is travelling for a long time before reaching earth) and tell the astronomers "point your telescopes there, in one hour you'll see something happening with that star". $\endgroup$ Commented Dec 20, 2015 at 23:35