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

Time and Quantum Mechanics

I’ve submitted an extended abstract for my paper “Time and Quantum Mechanics” to the Center for Philosophy of Science’s workshop on Quantum Time. I’m not sure what the odds are of my getting in, but at a minimum prepping the abstract for the center has been a big help getting the paper organized, working out what is essential to the argument, and what can be let go.

Note the abstract is more extended than abstract, about two pages:


Invisibility: Theory & Practice

I’ve posted my talk on the Theory & Practice of Invisibility  to ShareShare.  I’ve given the talk at Balticon, FOSSCON, & Capclave, & will be giving it at Philcon in a few weeks.

At Capclave, NASA asked if I would give it at their Goddard Space Center, once the sequester is lifted.  Nice to be asked!

Balticon records the talks in the science track, so at some point a video record should be online.  The last page on SlideShare has the references; I’d start there.

I’m not really sure why I decided to do invisibility for Balticon; Miriam Kelly, who organizes the science track at Balticon, asked me what I was going to talk about this year, & the next morning I woke up knowing the title.  Then there was the awkward few weeks while I tried to attach a talk to the title.

It’s a great subject; the main problem was really to throw enough out that the rest would fit into a 50 minute hour.  Seemed to go OK, lots of questions during the talk & afterwards in the halls.  That’s the real test.

One thing I like about the subject is that it leads in so many directions, among which:

  1. It’s about the math.  One of the limiting factors is just getting enough control over the mathematics of bending light to create the appropriate cloaking effect.  Any subject that borrows math from general relativity in the interests of simplifying itself is complex!
  2. It’s about the money.  The more money, the more transparency! In general, you can make things invisible from specific angles, over specific frequency ranges, to a certain level of quality.
  3. It’s not about the media:  the general approaches for making something invisible are the same for visible light, for radar, for sound waves.  One application under discussion is to make cities invisible from earthquakes:  arrange for the seismic shocks to pass around the city for instance.
  4. The hype to results ratio is still pretty high.  This is normal when an area is just starting; longer term, the most important uses are likely to be ones we haven’t even dreamt of.
  5. Making  things invisible & making them visible are two sides of the same coin, like attack & defense in war, to master either we must master both.
  6. And, finally, while the future of invisibility may not be clear, our motives in studying it are transparent: it’s interesting, potentially profitable, and fun.



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