Category: Time Machines

Time to the Power of Tim

Three Time Travel Tales by Tim Powers

Three Time Travel Tales by Tim Powers

This year the guest of honor at Capclave was Tim Powers. (Capclave is the Washington DC Science Fiction convention.) Tim is not only the author of many fine science fiction novels, but a very nice guy.

This turned out to be a good thing, as the initial proposal was to have Tim & I appear together and do something physic-y about his novels.  I have never done a talk with a live author before (dead authors are no problem, I have that down cold), so I was a bit nervous about the whole thing.

But it worked out well:  Tim was very helpful & gracious and when the audience asked him if one of my theories about the time travel in his novel The Anubis Gates was correct he said, essentially, “Now it is.” 🙂

I focused on three of his novels, The Anubis Gates — his first big success (with romantic poets & time-traveling Jackel Gods), Three Days to Never — something like the bastard child of John Le Carre & H. P. Lovecraft, and Medusa’s Web — who can resist the Time Spyders?

One of the distinctive features of Tim Powers working method is that he starts with a place and a time, researches it looking for the curious facts, bizarre details, & strange omissions that point to an unknown but dark reality, then gradually teases out the true story of whatreallyhappened!

“I made it an ironclad rule that I could not change or disregard any of the recorded facts, nor rearrange any days of the calendar – and then I tried to figure out what momentous but unrecorded fact could explain them all.”

So Tim builds his novels from the bottom up. As a result, they tend to differ wildly from each other.  Other authors, once they have got a setting that works, tend to reuse it, Tim builds anew each time.  No ten volume trilogies here!

And he also works out the timelines of all of his critical characters.  At each moment, he knows where each of his on and off stage characters are & what they are up to.  His notes on this are a kind of secret history of the secret history!

He has 20 or more novels out, so I focused on just three, all involving time travel.  And in each the theory of time travel was radically different!  I had a lot of fun linking each up to the corresponding physics and going back & forth about all this with my stage-mate Tim. 🙂

The talk, minus alas, the actual talking, is now up on slideshare.  Download if you will & any questions/comments please let me know!  thanks!



Stargates: The Theory & Practice

Doors and Portals and Stargates, Oh My!

Call them Stargates, Jumpgates, Fargates, Hypertubes or just an invitation to every unwanted pest from the far reaches of the Galaxy to visit, they are absolutely necessary if we are to have the glorious Science Fiction action we desperately need.  But could they actually be built?  We look at what modern physics has to say:  how to glue black holes together to build a wormhole, how to avoid the dangers of spaghettification, radiation poisoning, and paradox noise, and just what it would take to build one in practice.

This was a talk I did at the last Philcon, went over well.  And I had a lot of fun doing it.  I’ve got it up as a talk on slideshare.  And I may do variations on this at the 2017 Balticon & also Capclave.

It is the kind of subject you can go anywhere with!


Red Letter Days in the Time Traveler’s Almanac

The Main Line SF Book Discussion Group (is that the official name Denise?) which meets the third Tuesday of each Month at 7:15pm at Mainpoint Books, is doing the Vandermeer’s Time Traveler’s Almanac at our next meetup March 17th.

I’m pleased with this collection:  I’m a big fan of time travel & try to read  everything on the subject that doesn’t involve a strong yet sensitive woman going back in time to the Scotland of the clans & claymores to help a rough yet sensitive Scottish chieftain find true yet sensitive love.

The Vendermeers have done a good job of getting a wide range of good stuff.  There are some clunkers (avoid getting yourself trapped into Loob’s time loop) but overall average good & some standouts, including several I had not seen before.

The MLSFBDG decided we’d pick a few of the 80 odd stories to focus on.

Herewith my own favorites.  I used a really simple test:  I had already read thru the volume; these are the ones I particularly found myself wanting to read again.

  • Needle in a Timestack — love & time travel, spreadsheet time where you can feel the changes when you personal time line is recalculated
  • The Gernsback Continuum — the glorious futures of the lamented past, and a great addition to my collection of Imaginary Books: The Airstream Futuropolis:  The Tomorrow That Never Was
  • Triceratops Summer — cabbage stealing triceratopses & a meditation on impermanence
  • A Sound of Thunder — the classic butterfly effect story
  • Vintage Season — tourism more fun for the tourists than the tourees
  • Fire Watch — what can’t be changed can be remembered, is it enough?
  • Under Siege — George R. R. Martin shows his usual delicate concern for his character’s well-being
  • Traveler’s Rest — “No one knew what really happened to Time as one came close to the Frontier…”
  • At Dorado — her past is his future
  • Red Letter Day — curiously appropriate title for an almanac, interesting balancing act between free will & the desire to know how it will come out

And some more, likely to be good for discussion:

  • Ripples in the Dirac Sea — reminiscent of the Stevenson’s the Bottle Imp
  • Himself in Anachron — time & self-sacrifice
  • Time Travel in Theory and Practice — good review of the basics
  • The Final Days — Iron Man thinks the time travelers are watching him because he is about to do so well
  • On the Watchtower at Plataea — the time travelers are there to view the Peloponnesian War but get caught up in a war of their own
  • The Gulf of Years — love & bombs
  • Enoch Soames — time travel deal with the devil
  • Palindromic — opposite arrows of time collide
  • Delhi — time ghosts in Delhi, intriguing
  • Terminos — bottled time (see Tourmaline’s Time Checks, Momo) with an interesting narrative method
  • The Waitabits — classic Analog story-with-a-point: slowly, slowly, they get conquered that move fast
  • Music for Time Travelers — non-fiction
  • As Time Goes By — Tanith Lee channels her inner Moorcock, with a bit of Robert Service: “The nature of time, What do we really know about it? Two thousand streams, and us playing about in them like salmon.”
  • Against the Lafayette Escadrille — carpe diem — a frequent theme of this collection: Fokkers, crinolines, & Confederate spy balloons.
  • Palimpsest — Stross does the reductio ad absurdum of Heinlein’s All You Zombies (recently made into a not-bad movie), Gerrold’s The Man Who Folded Himself, Asimov’s The End of Eternity. If you like your absurdum’s reductio’d, this is the tale.

Most of the rest were worth reading as well: the only real clunkers — personal opinion obviously — were Loob & Forty, Counting Down with its companion Twenty-One Counting Up.

If you want to get on the Book Discussion’s list, email Denise who will be glad to add you to the list.  And check out Mainpoint Books, which has provided & new & hospitable home for the group (even staying open late just for us!).

Invisibility, Anti-gravity, Ethics of Time Travel, & Balonium

I’ve just received my schedule for Philcon, being held in a bit over a week, November 8th thru 10th.  Curious collection of subjects, but looks like a lot of fun.  If you are in the Philly area, it would be great if you can come by!

Sat 1:00 PM in Crystal Ballroom Two (1 hour)


[Panelists: John Ashmead (mod)]

How do we hide a jet fighter, a tank, even a city from sight? For
millennia people have dreamt of invisibility rings, caps, & cloaks:
how close are we to Harry Potter territory? Progress in the last ten
years has been extraordinary, and, with some help from general
relativity, 3d printers, advanced photonics, and more than a pinch
of ingenuity, we can now bend, fold, & spindle light in ways
unimagined ten years ago
Sat 3:00 PM in Crystal Ballroom Two (1 hour)

[Panelists: John Ashmead (mod), Ed Bishop, Walter F. Cuirle, Jay

Both creating and negating gravity are very common tropes in science
fiction. It’s taken for granted in most Science Fiction that
spacecraft have normal gravity, although they do not spin. How this
is achieved is rarely discussed. Anti-gravity is nearly as common,
(and convenient for the plot).. Are either of these concepts
scientifically plausible? Could such a technology ever actually be


Sat 6:00 PM in Plaza II (Two) (1 hour)

[Panelists: John Ashmead (mod), Evelyn Leeper, Andrew C. Ely]

Everyone talks about killing Hitler in his crib, or stopping Booth
from shooting Lincoln. But if you could change the past, would you
Sat 7:00 PM in Plaza III (Three) (1 hour)

[Panelists: John Ashmead (mod), Darrell Schweitzer, John Monahan,
Sharon Lee]

From cavorite to kryptonite, science fiction fiction writers love to
add new elements to the periodic table. How do you create
convincing imaginary substances and what do you do with them

Talks now on Slideshare

I’ve uploaded a number of my more recent talks to Slideshare.  Physics, with occasionally a wee bit of speculation admixed:

  1. Thought experiments – talk done 1st April 2012 for the Ben Franklin Thinking Society.  Role of thought experiments in history, use by Galileo & by noted violinist, how they can turn into real experiments.
  2. Not Your Grandfather’s Gravity – done last year (2011) on the latest developments in the suddenly hot area of gravity.  The stuff on faster-than-light neutrinos is, alas, already out of date:  boring won:  looks as if the FTL neutrinos were due to experimental error.   But Verlinde’s entropic gravity is still one of the most promising lines of attack.
  3. Temporal Paradoxes – physics talk given at NASA’s Goddard Space Center 2011.  A slightly NASA-fied version of a talk I’d given at several SF conventions in 2010.
  4. Quantum time – physics talk given at Feynman Festival in Olomouc in 2009.  I did popular versions of that talk as well.
  5. How to build a (real) time machine – talk given at several SF conventions in 2009.
  6. Life, the Universe, & the Second Law of Thermodynamics.  Or, the Infinite Probability drive.  About the role of entropy in the universe, complete with Babelfish.  2008.
  7. Faster Than Light – talk on faster than light travel:  theory, practice, applications. Given at several SF conventions in 2007.
  8. Confused at a Higher Level – arguably one of the funniest talks ever given about problems in quantum mechanics. OK, competition not that fierce.  Given at several SF conventions in 2004.
  9. The Physics of Time Travel.  Review of time, with respect to the bending, stretching, folding, & tormenting thereof.  Given at Philcon & Balticon (in various versions) in 2003.
  10. The Future of Time Travel – mostly about the science fiction thereof.  Probably 2002.

These are not all of my talks — I’ve probably done 20 or 30 SF talks over the last 20 years, at least one per year — these are just the ones done using Keynote or Powerpoint.  The 2005 & 2006 talks have gone walkabout.  If they reappear, I will upload.  I generally talk at Balticon, Philcon, & more recently Capclave.  I’ve spoken twice at Farpoint, but that is really more of a media convention, not as good a fit.

Talks before 2002 were done with Word & overheads. Overheads are easier to make than slides, but have a tendency to get bent, flipped, out of order, or in one especially memorable talk:  burnt.  That talk I was doing at the Franklin Inn Club: the projector failed at the last minute & I had to rent another from a nearby camera shop.  The rented projector ran hot. If I stayed on a specific slide for more than 60 seconds, the slide began to smoke.  Literally.  Colored smoke of course, wafting in strange tendrils towards the ceiling. Taught me a lot about pacing, mostly to make it faster.
By the way the word you are looking for, in re me & time travel, is not obsessed, it is focused.  Let’s just be clear about that.

Other talk(s), marginally less speculative:

  1. Overview of Backbone – talk on the jQuery library Backbone, given at PhillyCoders. April 2012.
  2. How to Destroy a Database – talk on database security.  October 2007.  Wile E. Coyote & other experts on correctness & security are enlisted to help make key points.
  3. Getting started with MySQL – talk given at PACS and my Macintosh programming group in 2006. Manages to work in the Sumerians, the Three Stooges, a rocket-powered daschhund, some unicorns, and – of course – dolphins (the totem animal of MySQL).

New Hope for Space War


I’m on the Space War panel at Balticon, how & why.  Fun topic though in all candor, a bit implausible.

The main problem is that travel in space is likely to be slow, expensive, & a bit dangerous.  Given this, it is likely that space travel itself will be reserved for moving stuff that is light weight & of very high value:  information, pharmaceuticals, experts, embryos, the “unobtainium” that features in Avatar, and so on.  Bullets satisfy neither test & even nukes have a hard time.

And if it takes a century to get over to the enemy’s star, why bother having the war?  And what are you fighting about anyway?  To have a war you have to be close enough to do some damage in a reasonable time frame & similar enough to have common — if opposed — objectives.

I owe the initial observation about the high costs of space travel to Paul Krugman, the Nobel-prize winning economist.  In the spirit of not pointing out problems without also pointing out a solution, he has found an economically viable use for space war:  as a way to generating a badly-needed stimulus, a kind of weaponized Keynesianism.

Given that there is now new hope for space war, and to get me in the right frame of mind for the panel, I list ten of my favorite space war novels:

  1. The War of the Worlds by H. G. Wells.  The number one space war novel.  The evil octopi are defeated by our germs. Great idea; two problems:  1) germs have to co-evolve to be effective against a host; ours probably would have no effect on the Martians and 2) real octopi are fun:  they play pranks on their experimenters & are great communicators as well.  With their ability to change skin color at will, octopi are practically eight-tentacled color television sets.
  2. The Lensman series by E. E. “Doc” Smith.  Six deathless volumes, each with at least two space-shaking interstellar battles. Chlorine breathers beware!  The oxygen breathers of the galaxy have found your secret base & are going to reduce it to a glowing pile of molten rock.
  3. Which is pretty much what happens to the lunar military base in Arthur Clarke‘s Earthlight.  Three Federation cruisers duel it out to a jointly fatal draw with a lunar fortress.  The war is about mineral rights & induced by attacks of mutually assured dementia, making the physics (this is Arthur C. Clarke!), the war, & the politics pretty realistic.
  4. Starship Troopers by Robert Heinlein.  Heinlein wrote about space suits in his pre-WWII SF, then used ideas from his stories when helping to design pressure suits for our fighter pilots in WWII, then used ideas from those pressure suits for his Have Spacesuit, Will Travel juvenile and for Starship Troopers: a beautiful example of the inter-relationship of reality & SF.  The space combats are a bit less stupid than most; Heinlein understands something of the difficulty of taking a space war to an underground enemy.
  5. The Forever War by Joe Haldeman.  This is partly a reaction to the Vietnam War & partly a reaction against Starship Troopers.  The forever war starts by accident, proceeds by error, and lasts for over a thousand years:  both humans & aliens are restricted to sub-light travel, so the war plays out in slow motion.  One of the few successful space war stories that works with existing physics.
  6. Keith Laumer’s Bolo Series.  Laumer wrote a long series of stories about Bolos, giant sentient tanks that are every adolescent male’s dream weapon.  In practice, they would likely be an economic & military disaster:  witness some of the late stage Nazi vehicles:  mechanically problematic, too heavy for bridges, & absorbing a disproportionate share of the military budget.  See Arthur Clarke’s delightful story Superiority.
  7. Dan Simmon‘s Hyperion series, especially the 2nd volume, The Fall of Hyperion, which concludes with a beautifully realized space battle between two fleets for control of a planetary system.  The inevitable confusion & long delays of such a battle are foregrounded.
  8. Catherine Asaro‘s Skolian Empire series.  Asaro has a physics background, gets existing physics right, & invents as much as she needs to keep the action fast-moving & interstellar.  The space combats are realistic:  long periods of nothing, brief high velocity exchanges of fire & then more long pauses while the surviving opponents regroup & turn around.  They remind me of the lance combats in White’s The Once & Future King.
  9. David Weber’s Honorverse series, starting with Manticore Station.  Weber is another author who tries to “get it right”.  The politics are modeled on the dueling ship combats of the Napoleonic wars, with wormholes to get realtime star to star travel without invoking faster-than-light mechanics (which would imply time-travel & a lot of confusion:  it is very rough on a space navy to first have triumphantly triumphed & then never to have been in the first place!).  He sets up the physics & weapons so that the ships even have broadsides, includes relativistic time dilation, and so on.  Weber’s Honor Harrington owes her “H’s” and general command style to C. S. Forester‘s Horatio Hornblower.  In a video game version of the Honorverse, it turned out that realistic implementing the physics/combat implied a near-planet maneuver (wish I could remember what it was) that invalided much of the combat in the novels.  With the infinite authority of the auteur, Weber passed a treaty that banned the disastrous trick.
  10. And I’ll finish with John G. Henry‘s Lost Fleet series.  The first six volumes reset Xenophon’s Anabasis in a medium-future space-faring context, again with wormholes connecting selected star systems.  A nearly destroyed fleet has to work its way back home in the face of enemy attack, mutiny, and sheer running out of resources.  Henry’s focuses on the many conflicting pressures on his commander, Jack Geary, as Geary balances military requirements, the demands of honor, & the imperatives of law, democracy, and a forbidden love.  The space combat — Henry used to be a ship driver in the US Navy – takes place in four dimensions and with admirable clarity about the command difficulties created by the finite speed of light:  if the enemy is on the far side of a solar system, he will see your maneuver only hours after you make it — and you will see his response hours after that.  You have to factor his response — and the responses of your detached units — into every move you make.  It is like blindfolded chess where you don’t find out the enemy’s move until after you have made three more moves of your own.  And your pieces are moving on their own.

And a couple of titles to avoid:

  • Anything by C. J. Cherryh, as least as far as space combat goes.  I remember reading one of her novels where the defenders had an advantage because they were at rest. In space, both sides are at rest with respect to themselves; the comment & resulting tactics were just nonsense.  Nonsense on stilts.
  • Gordon Dickson’s Dorsai series.  Omni-competent genetically enhanced uber soldiers trash lots of stooges.  The “ho” meets the “hum”.

So, my minimal requirement for space war in science fiction(not counting the golden classics of one’s youth of course) is that the humans, the physics, & the space war should make at least a bit of sense.

Temporal Paradoxes Talk Done: World Safe for Grandfathers

Had a very good time at NASA’s Goddard Space Center doing my talk Temporal Paradoxes.  Nice crowd; lots of good questions.  NASA’s audio-visual support was first rate, as you would expect, and the talk should be up on their site in a bit.  I’ll post a link here when that happens.

I’d like to thank Brent Warner & his colleagues for their warm welcome & all the feedback during the talk.  Brent tells me he particularly liked the quote from an Astounding Science Fiction reader (1933):

“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”*

As I say in the talk, if the current literature is on target, the grandfather & other paradoxes are cancelled out by interference by the time machine’s wave function with itself.

Brent & his NASA colleagues were kind enough to provide lunch & a fascinating tool of the facilities:  they manage the Hubble & are working on the James Webb.  Huge rooms with vast devices for subjecting equipment to high G’s, vacuum, heat, noise, vibration, & every other insult that it will need to be able to withstand during launch or in space:  gives one a real sense of just how hard it is to get this stuff to work!

*as quoted by Paul Nahin in his Time Machines: time travel in physics, metaphysics, and science fiction

Temporal Paradoxes Talk Online

I had a lot of fun putting my NASA talk Temporal Paradoxes together.  The feedback I got from the assembled multitude at the Radnor Library last week was extremely helpful, leading to a near complete rework of the talk, in the interests of making it clearer.   Thanks!

The pdf & keynote versions are now online.

Practice Run Thru on Temporal Paradox Talk

I’m doing a practice run thru on my Temporal Paradoxes talk at NASA.

The run thru will be at the Winsor room at the Radnor Memorial Library on March 12 at 2pm.  This is a few hundred feet from the main intersection in Wayne, PA.

The talk is basically the Physics Of Paradox talk, but more focused on the physics than the science fiction (tho in this area it can be hard to tell them apart) & with animations.

Since this is a complete redo of the talk, I’m hoping to get feedback on timing & clarity & focus & such like!

Please come!  And criticize!


— John Ashmead

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.

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