[FoRK] Inertial Mass != Gravitational Mass?

Jeff Bone jbone at place.org
Sat Jun 19 02:51:37 PDT 2010

Sent from my iPad

On Jun 19, 2010, at 2:04 AM, Harish Singh <senqua at googlemail.com> wrote:

> JB.
> No monkeys zipping around the cosmos yet. Yet, researchers, John
> Singleton and Andrea Schmidt of Los Alamos and their colleagues, have
> built a sort of wire in which an electric pulse can outpace light.
> Singleton says the basic principle of FTL currents goes back to work
> by English physicist Oliver Heaviside and German physicist Arnold
> Sommerfeldt in the 1890s, but was forgotten because Einstein's
> theories dissuaded physicists from thinking about FTL phenomena, even
> those that evaded the theories' strictures. I've only just touched on
> this engrossing physics and I recommend you read the team's papers,
> beginning with this one. "People just don't think about things moving
> faster than the speed of light," Singleton says. "This is a completely
> wide open and unexplored field."
> Fascinating stuff.
> http://www.scientificamerican.com/blog/post.cfm?id=faster-than-light-electric-currents-2010-06-18
> http://arxiv.org/abs/0903.0399
> - Harish
> Fascinating stuff.

No doubt.  Minor quibble, though:  lots of folks think seriously about that kind of thing.    

Long history of this sort of thing.  Had already seen this particular bit of work.

Another fun hack:  slow light down.  You can use a Bose-Einstein condensate for that.  Then you can go "FTL" on a bicycle...  A little extrapolations from existing experiments along that front even get you time travel w/o any significantly advanced technology from what we have today.  Curiously, nobody's built a time machine yet.  The Nazis tried, and there's a rather wacky scientist with a fixation on seeing his dead cater again that's picking at it, but...  Nobody doing it yet or apparently ever in our future history;  apparently we aren't overrun with tourists from the future or T800s or whatever, the occasional prankster notwithstanding.  No hedge funds using future data to vacuum out the world economy.

Similarly non-locality via entanglement.  Apparent c violation, but no causality violations.

But:  nothing yet that is even theoretically useful.  You can't even use it to transmit information, for reasons well understood and rarely questioned.

There have been a few papers lately demonstrating that even Alcubierre-style warp drives that use exotic matter to move a bubble inertial reference frame FTL relative to its starting frame probably result in a non-survivable experience.  Makes perfect sense and even sort of indirectly supports the conjecture I mentioned;  as you push through the vacuum the "bow spray" stirred up from the vacuum energy becomes an exceedingly dense radioactive wall...  And that's assuming you can get the "exotic" matter (I.e., unobtanium) to do it in the first place.

Then there's the little matter of causality.  Assuming Lorentz invariance of the space-time 4-manifold, FTL = time travel and causality violation.  If you read Eintein's own description of the origins of the idea, you'll find that, really, justifying causality was a the primary motivation rather than a side effect.  Those damn fence-jumping cows ruined it for all of us. ;-)  A bit of a red flag for me...

But as it turns out, whatever the operative mechanics and dynamics, reality looks close enough to GR to imply that the various constraints hold: the c limit seems to be not just a good idea, but the law.  

Apropos my conjecture, the point was this:  any FTL strategy for interstellar that's been seriously proposed requires implausible amounts of energy.  Direct acceleration requires getting past the asymptotic infinite energy condition the closer you get to c.  Warping space to avoid it requires, well, nobody knows.  Unobtanium for sure.  Doc Brown amounts of gigawatts, times many orders of magnitude. My conjecture, though it does imply vastly more accessible energy, doesn't get around this; indeed, it moves the speed limit back.  It's as if a ship moving through the sea could harvest the hydro-energy of the waves as it cuts through the water.  But at some point, the faster the ship goes the denser the water becomes, up to a limit of about 2/3 the speculative limit, when the sea ahead becomes an impenetrable solid for practical purposes...

The only thing my conjecture supplies that is novel is a different interpretation of the origins of inertial mass and gravitational curvature.  Both are seen not as the local effect of local mass on local space but rather the local effect of the sum of the residuals of all non-local wave functions vs. the Pauli exclusion of those states by the presence of local mass, ironically an "empty hole" relative to the surrounding vacuum energy density --- obeying a familiar curvature relation but for exactly the opposite reasons than those usually given.  Absent local mass, an object merely experiences rest of the universe "pushing" against it quasi-uniformly in all directions.  With local mass, it pushes the object towrds it. And there you have Newton's second law and the Reimann tensor, neatly bundled with a physical interpretation compatible with quantum mechanics.  All the rest follows without any particular cleverness. The result still looks like GR at a coarse level and certainly the math is almost identical.  You still see the same curvatures and rotational characteristics, with some minor exceptions which coincidentally give us a kind of MOND in regions neither dense with local matter nor absent it, such as those, say, on the edge of what would be ordinarily perceived as a steep gravity "well" under GR.  Like out at the boundaries of a solar system.  And you get long range effects that explain various observations w/o dark matter / energy beyond the reasonably well understood vacuum energy.

But no warp drive here, as far as I can tell.  Much to the detriment of Steven's (and, to be fair, my own) romantic notions and wishful thinking.

Nice prospects for much more efficient intrasystem travel, fab, other energy-demand stuff, etc. though.  As long as you can get where you are going in acceptable time at a max cruising speed of 2/3 c (and somehow dodge the oncoming traffic) you can get around easily.  Don't even have to lug around propellant mass.  And the only unobtainium required is a lot more obtainable than the type usually required for applications of these kinds of wacky ideas.

Lastly: whatever the limits of practical physical space travel, hauling fragile and bulky meat-bags and all their annoying life support ecosystems around is just foolish, unless for some reason that's all you can do.  If you assume that you can get consciousness in digital form, on a dense and efficient solid-state substrate or even transmit it, things become MUCH more efficient and practical in every way.  The cosmos is *ideal* for machines / software; even ones that think they are or were once "human."


More information about the FoRK mailing list