Category: Popular

Temporal Paradoxes Talk at NASA

I’ve been asked to do a talk, Temporal Paradoxes, at NASA.  This will be on the 21st of this month, at 3:30pm.  This is a NASA-fied version of my previous Physics of Paradox talk, meaning more animations & less science fiction, and perhaps a few equations in a grayish font.  Abstract:

ABSTRACT — Einstein’s general relativity is the leading theory of gravity. Simple and elegant, it has passed all available experimental tests including: deflection of light by gravity, precession of orbital apsides, gravitational time dilation (used in GPS), and frame-dragging.

However, general relativity makes a number of counter-intuitive predictions. In particular, trajectories looping around massive, rapidly rotating stars or passing through a wormhole can close on themselves in time, creating closed timelike curves (CTCs).

This creates the possibility of “grandfather” and “bootstrap” paradoxes. Recent work by Greenberger & Svozil, and others, however, questions this conclusion. That work suggests that when quantum mechanical effects are included, the paradoxes become self-canceling, eliminated by destructive interference within the wave function. If the paradoxes are self-canceling, then closed time-like curves are possible. If they are possible, can we create or detect them?

Several authors have suggested that we look for evanescent wormholes with the Large Hadron Collider. If we find them, we may be at the edge of temporal paradox. While the only safe prediction in this area is that there are no safe predictions, we look at the implications of this for general relativity, quantum mechanics, & causality.

Reality versus free will, escaping the Holodeck, are the laws of physics “more guidelines than rules”?, and more!

I’m doing five panels and my Physics of Paradox talk at the Philadelphia Science Fiction Convention, starting in a few hours.

Quite a lot of fun subjects for my panels:  Augmented Reality (for those who can’t get enough reality), Time Travel & Free Will, Are the Laws of Physics Laws (or really more just Guidelines?), Is the Universe a Hologram (& can I leave the Holodeck?), my Physics of Paradox talk in its final & perfected version, & What Came Before the Big Bang (& are we in trouble with whatever it is?)

[I’ve augmented the reality of the Physics of Paradox slides by adding the spoken text to them:  see the Keynote (for Mac users), PowerPoint (for PC users), and  annotated pdf version.]

My complete schedule is:

Fri 10:00 PM in Crystal Ballroom Two (1 hour)
[Panelists: John Ashmead (mod), Earl Bennett, Rock Robertson, Bud Sparhawk]
We’ve all heard about virtual reality and the potential it holds for gaming, learning, medicine etc., but augmented reality, while less well-known, is more likely to have a major effect on everyday life. Imagine wearing a pair of glasses while driving that produce flashing arrows to indicate your turns, or looking at a city street through your cell phone screen and seeing each building labeled by name and type of business. Learn what’s happening now and what we can expect in the future.
Sat 11:00 AM in Plaza VII (Seven) (1 hour)
[Panelists: John Ashmead (mod), Michael F. Flynn, John Grant, Helen Collins, Lawrence Kramer]
Suppose that  three weeks in the future I come back and sit on this panel,does this not imply that nothing can happen in the future toprevent me from getting in a time machine and coming back? Does this mean that time travel implies that the future is pre-determined?
Sat 12:00 PM in Crystal Ballroom Two (1 hour)
[Panelists: Paul Halpern (mod), John Ashmead, Jay Wile, Tony Rothman]
Are the laws of nature really the same across all space and time? No principal is more fundamental to physics than the idea that the laws of nature remain the same at all times and in all places. Much we believe to be true about the universe depends upon this concept. However, new observations have revealed anomalies that suggest that such physical laws as the fine structure constant and the speed of light may actually have changed over time. Will we soon have to rethink our ideas about physics and cosmology
Sat 2:00 PM in Crystal Ballroom Two (1 hour)
[Panelists: Paul Halpern (mod), John Ashmead, Jay Wile, Tony Rothman]
Is the universe a hologram? One of the strangest ideas to come out of modern physics is the holographic principal, which speculates that the universe may be a multi-dimensional projection of information encoded (in Planck length-sized  squares, each containing one bit of information) on a two-dimensional boundary called the cosmological horizon. A new experiment searching for gravity waves may have accidentally found evidence for this theory that was predicted by supporters.
Sat 3:00 PM in Crystal Ballroom Two (1 hour)
[Panelists: John Ashmead (mod)]
There is nothing in modern physics to rule out time travel, save paradox.  And — thanks to quantum mechanics — it seems any potential paradoxes would be self-canceling.  Therefore the only thing standing between us and time travel is not knowing how to go about it, exactly.  But several recent papers have proposed ways to use the Large Hadron Collider at CERN to create particle loops that
go backwards in time.  Now what?
Sat 5:00 PM in Crystal Ballroom Two (1 hour)
[Panelists: John Ashmead (mod), Paul Halpern, Eric Kotani, Tony Rothman]
Was there a time before the beginning? As incredible as it seems, new discoveries have given scientists clues about what may have existed prior to the beginning of our universe. Scientists at the University of Pennsylvania have developed a mathematical model that traces through the Big Bang to a shrinking universe that exhibits physics similar to ours. Measurements of the Cosmic Microwave
Background radiation reveal an imprint from the earliest stages of the universe may also shed light on what came before. The following links are offered as jumping off points to potential panelists who would like to investigate this topic:

The Physics of Paradox — Followup

Gave the Physics of Paradox talk at the Library of Congress Thursday (10/21/2010) & then again at Capclave Saturday (10/23/2010).   Good audiences both times, lots of good questions.  At Capclave talk was standing room only & Brent Warner, from the Goddard Space Center has asked if I would be interested in doing it there this spring.

I made some changes to the talk over the weekend, in response to audience feedback & further reflection.  The latest version is now up as Keynote (for Mac users), PowerPoint (for PC users), PDF in slides-only and also annotated forms.

I’d like to thank Dick Ladson, Walt Mankowski, Bruce Bloom, Shelley Handen, Ed & Marguerite Rutkowski, & of course Ferne Welch for their feedback at the dry run, which improved it immensely.  And I would like to thank Nathan Evans of the Library of Congress & Colleen Cahill of Capclave (& as it happens the Library of Congress) for having me.  Lots of fun!

Time and quantum mechanics at the Chestnut Hill Book Festival

Spoke at noon yesterday (July 10th, 2010) at the Chestnut Hill Book Festival; in spite of heavy rain a nice crowd.
This was my Balticon Time & Quantum Mechanics talk, adjusted for a general (rather than a science fictional) audience.  I covered over a hundred years of physics in less than an hour — a lot — but the audience survived & even seemed to prosper, asking some good questions!
I’ve uploaded the power point and keynote versions of the talk so you can see the animations of the double slit experiment, if you have power point and/or keynote.  You may have to tell your browser how to handle .ppt and/or .key files, for all parts to work with maximum smoothness. I’ve also uploaded the pdf and html versions.
The references — several asked after them — are on slide 36.  Enjoy!
I’d like to thank Oz Fontecchio for organizing this, Ferne Welch for moral & practical support, Bob Rossberg (sp?) for critical help on the AV, & the Chestnut Hill Book Festival for providing the venue!

Time & quantum mechanics talk done

Did the talk Saturday evening as planned.  Very sophisticated audience: almost everyone there had heard of the double slit experiment!

The talk went over well:  audience enthusiastic; lots of good questions.  Post talk I was asked if I would do similar presentations for Capclave & for the Library of Congress.  Leaning in favor.

I think that to really get across quantum mechanics, especially in a short time, nothing beats animations; the animations of the single & double slit were probably the most effective bits.  In future talks I shall be more animated.

The animations were courtesy of Bernd Thaller’s Advanced Visual Quantum Mechanics. He provides a useful kit of Mathematica functions for building such; looks a good starting point.

I’ve uploaded the power point & keynote versions of the talk so you can see the animations of the double slit experiment, if you have power point and/or keynote.  You may have to tell your browser how to handle .ppt and/or .key files, for all parts to work with maximum smoothness.

The pdf & html versions are still present, of course.  These are the talk as delivered, slightly different from the version previously posted (I added several more slides on the quantum eraser).

Paradox Noise



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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Quantum time talk today

December 12th, 2009

One of the members of my Macintosh programming SIG asked me if for today’s meeting I would talk about Quantum Time, which I was, of course, happy to do.  There is nothing like explaining something to a bunch of intelligent listeners for getting it straight in your own head.  And if you can get across some of the wonder & the weird that is modern physics, that’s even better!

I’ve got the slides online (see under talks).  Summary:
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References on Time & Time Travel

Updated 12/2/2009

Recommended popular books on time. All of the authors know their physics; none are mortal enemies of the English language.  Enjoy:
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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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