Physics of Paradox

This talk — scheduled for the Library of Congress & for Capclave next week — is now up.

It was a lot of fun to put together:  I discuss time in relativity & quantum mechanics, kinds of time, some possible time machines, the three kinds of paradox (grandfather, bootstrap, & freewill), the Hawking & Novikov consistency conditions for avoiding paradox, some ways to implement those conditions, paradox noise, what the world might look like if paradox avoiding time travel were possible, and of course why this is likely.

I’ve got the talk on line as Keynote (for Mac users), PowerPoint (for PC users), PDF in slides-only and also annotated forms.

I’m doing a practice run on the talk in two days at the Radnor Memorial Library in the Winsor room from 6pm to 8pm (when we have to be out).  I start the actual talk about 6:30pm.  This is a dry run (well more of a wet run really) for the talks next week.

If you are not too far from Wayne, PA & have an interest in time & paradox (but then if not why are you reading these words?) please feel free to come!

Paradox Noise

“YOUR ONLY CHANCE LIES IN PREVENTING THE ASSASSINATION OF PRESIDENT ABRAHAM LINCOLN . . .” “What?” A burst of audio and visual static reduced reception to unintelligible noise. Then the paradox-generated interference was gone again, as suddenly as it had come. ” . . . Fourteenth of April at Ford’s Theater –” blast, crackle. “. . . you must be within two meters of the President . . . just before the bullet smashes into Lincoln’s brain. Your total window of opportunity will be three seconds.” – Fred Saberhagen’s After the Fact

If the block universe view is correct, if time is “nothing but” a space dimension, then we should be able to travel in it. Leaving aside the fact that we don’t quite yet know how to do this (but see some of the books under references) shouldn’t time travel be forbidden by the paradoxes it would otherwise make inevitable?  There are three kinds of paradox to consider:

Three kinds of paradox

Grandfather paradox

Why pick on grandfather? It seems that the only way to prove that time travel is impossible is to cite a case of killing one’s own grandfather. This incessant murdering of harmless ancestors must stop. Let’s see some wide-awake fan make up some other method of disproving the theory.

– 1933 letter to Astounding Stories, as quoted in Nahin’s Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction

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Five Popular Talks

Over the last ten or fifteen years I’ve done a number of slide talks at Balticon, Philcon, & Farpoint, three local science fiction conventions. A number of these have been relatively heavy on the physics – within the context of a science fiction convention of course – and I thought it might be fun to post them. As Rod Sterling might have put it, presented for your consideration:
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