Using the Casimir force
Dan Goodman
Physical Review Letters
Metamaterials could reduce friction in nanomachines
Nanoscale machines expected to have wide application in industry,
energy, medicine and other fields may someday operate far more
efficiently thanks to important theoretical discoveries concerning the
manipulation of famous Casimir forces that took place at the US
Department of Energy's Ames Laboratory.
US Department of Energy
Contact: Mark Ingebretsen
ma...@ameslab.gov
515-294-3474
DOE/Ames Laboratory
http://www.ameslab.gov/final/News/2009rel/Casimir.html
Confession: I don't know enough to understand this.
--
Dan Goodman
Journal at:
dsgood.livejournal.com
dsgood.dreamwidth.org
dsgood.insanejournal.com
alie...@gmail.com
> Public Release: 7-Dec-2009
> Physical Review Letters
> Metamaterials could reduce friction in nanomachines
> Nanoscale machines expected to have wide application in industry,
> energy, medicine and other fields may someday operate far more
> efficiently thanks to important theoretical discoveries concerning the
> manipulation of famous Casimir forces that took place at the US
> Department of Energy's Ames Laboratory.
> US Department of Energy
>
> Contact: Mark Ingebretsen
> ma...@ameslab.gov
> 515-294-3474
>
> Confession: I don't know enough to understand this.
Don't worry: Unc and I will understand it _for_ you. ;>)
Seriously, it'll be a huge breakthrough if it can be made to work.
I'm thinking there'll be a texture factor; one metamaterial will be
repulsive to another patch of the same stuff but attractive to other
metamaterials with different structures.
I'm vaguely remembering artificial-atom metamaterials; they could
provide reversibility.
Mark L. Fergerson
Eric Ammadon
>Public Release: 7-Dec-2009
>Physical Review Letters
>Metamaterials could reduce friction in nanomachines
>Nanoscale machines expected to have wide application in industry,
>energy, medicine and other fields may someday operate far more
>efficiently thanks to important theoretical discoveries concerning the
>manipulation of famous Casimir forces that took place at the US
>Department of Energy's Ames Laboratory.
>US Department of Energy
>
>Contact: Mark Ingebretsen
>ma...@ameslab.gov
>515-294-3474
>DOE/Ames Laboratory
>http://www.ameslab.gov/final/News/2009rel/Casimir.html
>
>Confession: I don't know enough to understand this.
"The Casimir effect was named after Dutch physicist Hendrik Casimir,
who postulated its existence in 1948."
Fascinating stuff, thanks for posting the link.
--
arggh, is it priate day again?
James A. Donald
> Public Release: 7-Dec-2009 Physical Review Letters
> Metamaterials could reduce friction in nanomachines
> Nanoscale machines expected to have wide application
> in industry, energy, medicine and other fields may
> someday operate far more efficiently thanks to
> important theoretical discoveries concerning the
> manipulation of famous Casimir forces that took place
> at the US Department of Energy's Ames Laboratory. US
> Department of Energy
>
> Contact: Mark Ingebretsen ma...@ameslab.gov
> 515-294-3474 DOE/Ames Laboratory
> http://www.ameslab.gov/final/News/2009rel/Casimir.html
>
> Confession: I don't know enough to understand this.
These guys want a repulsive Casimir force so that they
can scale machinery down to very small sizes.
The usual vision of nanotechnology is conventional
machinery scaled down to nanometer sizes. Observe that
biological organisms do not work anything like this,
relying on structures of slime and jelly driven by
thermodynamics, rather than rigid structures driven by
mechanics. Biology uses structures that resist our
intuition to design or to understand, for the
thermodynamics, rather than the mechanics, is primary.
Conventional machinery does *not* scale down to
nanometer sizes because of static friction. Static
friction is a macroscopic manifestation of the nanoscale
and mesoscale Casimir force. Scaling laws tell us that
as we build smaller and smaller machinery, static
friction becomes more and more of a problem, causing our
machinery to freeze up at the mesoscale, freeze up long
before we get down to the nanoscale, freeze up long
before we have to abandon such crude approximations as
static friction for more precise concepts such as
Casimir force.
So to get bits of mesoscale machinery to float freely
and not stick to each other, need a repulsive casimir
force, which is what these guys are trying to get.
Or alternatively, we can start figuring out how to build
out of slime and jelly, which has no problem with static
friction. I observe that proposals for scanning a single
DNA molecule, or synthesizing a single DNA molecule,
seem to be heading the slime route, so I am inclined to
believe it is more practical than repulsive Casimir
forces.
alie...@gmail.com
> --
> On Mon, 7 Dec 2009 20:31:50 -0600, "Dan Goodman"
>
> <dsg...@iphouse.com> wrote:
> > Public Release: 7-Dec-2009 Physical Review Letters
> > Metamaterials could reduce friction in nanomachines
> > Nanoscale machines expected to have wide application
> > in industry, energy, medicine and other fields may
> > someday operate far more efficiently thanks to
> > important theoretical discoveries concerning the
> > manipulation of famous Casimir forces that took place
> > at the US Department of Energy's Ames Laboratory. US
> > Department of Energy
>
> > Contact: Mark Ingebretsen ma...@ameslab.gov
> > 515-294-3474 DOE/Ames Laboratory
> >http://www.ameslab.gov/final/News/2009rel/Casimir.html
>
> > Confession: I don't know enough to understand this.
>
> These guys want a repulsive Casimir force so that they
> can scale machinery down to very small sizes.
Yep.
> The usual vision of nanotechnology is conventional
> machinery scaled down to nanometer sizes. Observe that
> biological organisms do not work anything like this,
That's not necessarily a bug...
> relying on structures of slime and jelly driven by
> thermodynamics, rather than rigid structures driven by
> mechanics. Biology uses structures that resist our
> intuition to design or to understand, for the
> thermodynamics, rather than the mechanics, is primary.
Yep.
> Conventional machinery does *not* scale down to
> nanometer sizes because of static friction. Static
> friction is a macroscopic manifestation of the nanoscale
> and mesoscale Casimir force. Scaling laws tell us that
> as we build smaller and smaller machinery, static
> friction becomes more and more of a problem, causing our
> machinery to freeze up at the mesoscale, freeze up long
> before we get down to the nanoscale, freeze up long
> before we have to abandon such crude approximations as
> static friction
...and hydrogen bonding, van der Waals, and other names for the same
range of forces.
> for more precise concepts such as Casimir force.
>
> So to get bits of mesoscale machinery to float freely
> and not stick to each other, need a repulsive casimir
> force, which is what these guys are trying to get.
Precisely.
> Or alternatively, we can start figuring out how to build
> out of slime and jelly, which has no problem with static
> friction. I observe that proposals for scanning a single
> DNA molecule, or synthesizing a single DNA molecule,
> seem to be heading the slime route, so I am inclined to
> believe it is more practical than repulsive Casimir
> forces.
I'm not so sure. Nature has had a long time to fine-tune those
slimes and jellies, while as you say they're outside our intuitive
base. Rather than forget miniaturizing conventional machinery and play
catch-up on slimes etc. from a dead stop we should proceed with what
we know (gears and levers, and like that) while catching up on slimes
etc. in parallel.
Also, remember that while getting those machines to manipulate
slimy, gelid structures may be awkward, the machines conversely will
be pretty much immune to the attacks of other autonomous mesoscale
"structures of slime and jelly" that come with their own
programming...
Mark L. Fergerson
James A. Donald
> > Or alternatively, we can start figuring out how to
> > build out of slime and jelly, which has no problem
> > with static friction.
"nu...@bid.nes"
> I'm not so sure. Nature has had a long time to
> fine-tune those
> slimes and jellies, while as you say they're outside
> our intuitive base. Rather than forget miniaturizing
> conventional machinery and play catch-up on slimes
> etc. from a dead stop we should proceed with what we
> know (gears and levers, and like that) while catching
> up on slimes etc. in parallel.
Buckey balls spin spontaneously within a buckeyball
crystal, which would suggest that conventional machinery
could be built that would function at nanoscale. On the
other hand, mesoscale machinery locks up, as one would
expect from scaling laws. Buckey balls spin not because
they approximate near frictionless ball bearings, but
because thermal vibration is large at that scale. If we
rely on thermal vibration to avoid locking up, our
machinery is going to have some characteristics
resembling slime and jelly.
Of course, if we can get casimir force to be repulsive,
then we can have vacuum bearings, classical machines as
envisaged by Drexler.
Jonathan L Cunningham
wrote:
>Public Release: 7-Dec-2009
>Physical Review Letters
>Metamaterials could reduce friction in nanomachines
>Nanoscale machines expected to have wide application in industry,
>energy, medicine and other fields may someday operate far more
>efficiently thanks to important theoretical discoveries concerning the
>manipulation of famous Casimir forces that took place at the US
>Department of Energy's Ames Laboratory.
>US Department of Energy
>
>Contact: Mark Ingebretsen
>ma...@ameslab.gov
>515-294-3474
>DOE/Ames Laboratory
>http://www.ameslab.gov/final/News/2009rel/Casimir.html
>
>Confession: I don't know enough to understand this.
I understand it well enough at the level it's written (i.e. vague about
details) that it makes sense to me, but is very surprising.
So surprising that I wonder if their (theoretical) calculations are
missing something. OTOH, the real, physical world is full of surprises,
and it's not an entirely crackpot organisation ;-) so maybe they're on
to something...
One easy way[*] to understand Casimir forces, which the article alludes
to, but doesn't state explicitly, relies on the quantum mechanical fact
that an oscillator has to oscillate: it can't be completely motionless
(this relates to the uncertainty principle, Schrodingers equation etc
etc. -- it comes out of the possible solutions to the equation.)
Basically, a quantum mechanical tuning fork *always* vibrates a bit, and
a pendulum *always* swings back and forth a bit. It can't not.
The article refers to energy waves. What this means is "electromagnetic
waves", i.e. radio, light, x-rays etc. In the gap between two surfaces,
the waves can bounce back and forth: these are called "standing waves"
and act like oscillators (or tuning forks, or pendulums). And,
therefore, the space is vibrating a bit, in every possible way.
(Incidentally, this vibration is what is called "zero point energy".)
But the crucial word there is "possible". Space doesn't vibrate in
impossible ways - that would be impossible. (Impossible things are
impossible, fortunately, otherwise we'd all get confused.)
In the gap between two surfaces, there isn't *room* to have standing
waves bigger than the gap: it's impossible. So *those* "tuning forks"
don't exist. So that part of the zero point energy doesn't exist. It's
this missing energy that gives rise to the attractive Casimir force.
(Or, to look at it another way, it's the extra vibrations *outside* the
gap which are pressing on the outside.)
Turning that around the other way: to get a repulsive Casimir force
would require fitting in *more* standing waves into the gap between
objects than you can get into a vacuum.
Which is why I'm suprised, if it's possible. It's a bit like fitting
more junk into my living room by filling it full of other stuff first.
OTOH, you *can* do that with electromagnetic waves by changing the
dielectric constant of the material (google on "dielectric constant")
which acts a bit like the Tardis, as far as e.m. waves are concerned.
Hmmm. Time for an "incredible shrinking man" story, I think...
Have you ever wondered how the Tardis is bigger on the inside than on
the outside? I have. One way to do that is that it isn't: the door into
the tardis shrinks people and things as they go through, and enlarges
them again on the way out...
The real tardis does't do that, of course. It really is bigger on the
inside.
Jonathan
[*] There are other ways to look at it too. All different, and many are
correct (just like the rasfc slogan: nine-and-sixty ways). You pays yer
money and takes yer choice. To put it another way: theories are tools to
understand the world. And you use the best tool for the job: you *can*
hammer in screws with a chain-saw...
--
Writers: Many are called, but few are chosen.
Giovanni
news:4b1fa25d...@news.btconnect.com...
> On Mon, 7 Dec 2009 20:31:50 -0600, "Dan Goodman" <dsg...@iphouse.com>
> wrote:
>
>>Public Release: 7-Dec-2009
>>Physical Review Letters
>>Metamaterials could reduce friction in nanomachines
>>Nanoscale machines expected to have wide application in industry,
>>energy, medicine and other fields may someday operate far more
>>efficiently thanks to important theoretical discoveries concerning the
>>manipulation of famous Casimir forces that took place at the US
>>Department of Energy's Ames Laboratory.
>>
> Have you ever wondered how the Tardis is bigger on the inside than on
> the outside? I have. One way to do that is that it isn't: the door into
> the tardis shrinks people and things as they go through, and enlarges
> them again on the way out...
>
> The real tardis does't do that, of course. It really is bigger on the
> inside.
I seem to remember that Scrooge McDuck was there, done that (Tardis-like
building) much earlier than the good Doc.
Not by the Casimir, though. Possibly a Gyro Gearloose patent?
Any bibliographic hint gratefully accepted.
Giovanni
Bill Swears
> But the crucial word there is "possible". Space doesn't vibrate in
> impossible ways - that would be impossible. (Impossible things are
* (Unless you are a Marine).
Eric Ammadon
Brian M. Scott
<wsw...@gci.net> wrote in
<news:vqidnabI255UToLW...@posted.mtasolutions>
in rec.arts.sf.science,rec.arts.sf.composition:
> Jonathan L Cunningham wrote:
Aren't you thinking of the WWII motto of the U.S. Army Corps
of Engineers?
Brian
Bill Swears
Bill
--
Living on the polemic may be temporarily satisfying, but it will raise
your blood-pressure, and gives you tunnel vision.
Brian M. Scott
<wsw...@gci.net> wrote in
<news:abudna-2ffz3nL3W...@posted.mtasolutions>
in rec.arts.sf.science,rec.arts.sf.composition:
> Brian M. Scott wrote:
>> On Wed, 09 Dec 2009 07:43:53 -0900, Bill Swears
>> <wsw...@gci.net> wrote in
>> <news:vqidnabI255UToLW...@posted.mtasolutions>
>> in rec.arts.sf.science,rec.arts.sf.composition:
>>> Jonathan L Cunningham wrote:
>>>> But the crucial word there is "possible". Space doesn't vibrate in
>>>> impossible ways - that would be impossible. (Impossible things are
>>>> impossible, fortunately, otherwise we'd all get confused.)*
>>> * (Unless you are a Marine).
>> Aren't you thinking of the WWII motto of the U.S. Army Corps
>> of Engineers?
> The impossible takes a little bit longer?
Yep.
Brian
Ben Crowell
> Public Release: 7-Dec-2009
> Physical Review Letters
> Metamaterials could reduce friction in nanomachines
> Nanoscale machines expected to have wide application in industry,
> energy, medicine and other fields may someday operate far more
> efficiently thanks to important theoretical discoveries concerning the
> manipulation of famous Casimir forces that took place at the US
> Department of Energy's Ames Laboratory.
> US Department of Energy
>
> Contact: Mark Ingebretsen
> ma...@ameslab.gov
> 515-294-3474
> DOE/Ames Laboratory
> http://www.ameslab.gov/final/News/2009rel/Casimir.html
>
> Confession: I don't know enough to understand this.
>
Hey, Dan, nice to hear from you! I had just been wondering if you'd
dropped out of this group, hadn't seen your posts in a while.
I assume this is the same thing:
http://www.technologyreview.com/blog/arxiv/24499/
One thing I didn't really understand (after an admittedly cursory
reading) was this. It still requires you to have just as big an
energy source as with other methods of propulsion. It gets you out
of having to carry around reaction mass, but as far as I can tell
that just means you're satisfying conservation of momentum by
emitting electromagnetic waves as your "exhaust." If that's the
case, then how is it any better than simply propelling yourself
using the reaction from a laser (which has got to be the world's
crappiest imaginable method of propulsion)?
Ric Locke
No, Ben, it's more analogous to a screw propeller, an airplane or ship.
Grab (virtual) particles and shove them aft before they go away, and you
get a change of momentum.
Not that I believe it yet, but it's an interesting thought.
Regards,
Ric
Eric Ammadon
If you make things tiny enough the parts are going to stick together,
the same way all the molecules in a piece of plastic stick together,
for the same reasons. You can use tiny parts of dissimilar materials
that don't bond to one another, or you can make the parts big enough
and the fit sloppy enough that molecular bonding isn't an issue, or
you can pursue some magical force that will keep the tiny pieces from
sticking together and find out that you've invented a disintegration
method and your tiny machines still don't work. <g>
Ric Locke
> method and your tiny machines don't work. <g>
One of the things I find intriguing about research into nanoscale stuff
is the possibility of making powder metallurgy and ceramics work better.
In both cases you take a fine powder, form it into the shape you want by
molding or whatever, then subject it to a process that causes the
particles to cohere. In ceramics it's partly a chemical reaction; in
powder metallurgy it's heating it to the point where the atoms start
interacting with one another, generally 'way below the melting point --
in fact, that's part of the reason for using it in preference to
casting. Both are ways to make things out of materials that are
refractory and hard to machine.
If we understood the forces well enough to overcome them, we would also
understand them well enough to promote them. Ceramics are generally
brittle, and therefore weaker than they should be, because depending on
the chemical bonds leaves weak spots. Parts made by powder metallurgy
aren't completely dense, because the particles don't pack perfectly. If
we could make ceramics without the chemical reaction, or get powder
metallurgical parts to completely densify, we would be coming real close
to the "universal fabricator" sometimes featured in SF.
Regards,
Ric
Dan Goodman
Yes, but what IS it?
> Fascinating stuff, thanks for posting the link.
--
Ric Locke
As short as I can make it: Spacetime is filled with virtual particles.
They appear out of nothing in antimatter-matter pairs and promptly
annihilate one another, so conservation of energy is not mocked -- the
net is zero.
That's one way of looking at it. Coming from the other direction, if you
work through the equations of spacetime and apply them to empty space,
you get a ginormous number -- the "vacuum energy" -- which dwarfs the
energy content of any matter that might happen to be there. This made no
sense to the mathematicians and cosmologists who derived the result, so
they shrugged and called that "zero" for a long time.
As is usual in physics at that level, both explanations appear to be
"true" depending on which set of phenomena you are observing. The
"particle" or quantum physics version is the basis for Hawking's
prediction that (small) black holes evaporate, and is currently being
used to derive some very strange results. (One of them is that the
Universe is two-dimensional; the third dimension is a holographic
illusion. Nobody knows, yet, if that's "true" in the sense of leading to
further useful results.) The spacetime/vacuum energy version is an
inevitable result of the mathematics, and too many people have
re-derived that result for anybody to question that it's there, although
there are /many/ questions cognate with "what does it /mean/?"
Casimir suggested that if two objects were in close enough proximity the
effect of the particles in the objects would be to stress spacetime and
reduce the vacuum energy. The quantum way of looking at it would be that
there was no room for the virtual particles to form. Either way, there
would be an effect analogous to vacuum between the objects -- the energy
on the other side of them would force them together. He built an
experiment to test the hypothesis, and lo! the force appeared, exactly
as predicted, so they named it after him.
The magnitude of the vacuum energy is such that if we could get, say,
one thousandth of one percent of the virtual particles to hang around
for a few nanoseconds and control the result, we could power the world
from a three-meter sphere. This is considered unlikely, but is (to put
it mildly) of interest. The Casimir Effect (or Force) looks like the
only crack in that wall, and there are several very clever people trying
to insert some extremely sophisticated crowbars into it.
Regards,
Ric
Don Bruder
Bill Swears <wsw...@gci.net> wrote:
> Brian M. Scott wrote:
> > On Wed, 09 Dec 2009 07:43:53 -0900, Bill Swears
> > <wsw...@gci.net> wrote in
> > <news:vqidnabI255UToLW...@posted.mtasolutions>
> > in rec.arts.sf.science,rec.arts.sf.composition:
> >
> >> Jonathan L Cunningham wrote:
> >
> >>> But the crucial word there is "possible". Space doesn't vibrate in
> >>> impossible ways - that would be impossible. (Impossible things are
> >>> impossible, fortunately, otherwise we'd all get confused.)*
> >
> >> * (Unless you are a Marine).
> >
> > Aren't you thinking of the WWII motto of the U.S. Army Corps
> > of Engineers?
> >
> > Brian
> The impossible takes a little bit longer?
>
> Bill
We the unwilling,
led by the unknowing,
are doing the impossible for the ungrateful.
We've been doing so much, for so long, with so little
that we are now qualified to do anything using nothing.
- Damned if I know where it comes from, but it was one of my father's
favorite things to say when some idiot came along asking him to do
something that was obviously going to take a metric buttload of time,
money, and hard-to-get materials - if it could be done AT ALL...
--
Email shown is deceased. If you would like to contact me by email, please
post something that makes it obvious in this or another group you see me
posting in with a "how to contact you" address, and I'll get back to you.
Dan Goodman
> although there are many questions cognate with "what does it mean?"
>
> Casimir suggested that if two objects were in close enough proximity
> the effect of the particles in the objects would be to stress
> spacetime and reduce the vacuum energy. The quantum way of looking at
> it would be that there was no room for the virtual particles to form.
> Either way, there would be an effect analogous to vacuum between the
> objects -- the energy on the other side of them would force them
> together. He built an experiment to test the hypothesis, and lo! the
> force appeared, exactly as predicted, so they named it after him.
>
> The magnitude of the vacuum energy is such that if we could get, say,
> one thousandth of one percent of the virtual particles to hang around
> for a few nanoseconds and control the result, we could power the world
> from a three-meter sphere. This is considered unlikely, but is (to put
> it mildly) of interest. The Casimir Effect (or Force) looks like the
> only crack in that wall, and there are several very clever people
> trying to insert some extremely sophisticated crowbars into it.
>
> Regards,
> Ric
Much thanks!
Dan Goodman
> Dan Goodman wrote:
> > Public Release: 7-Dec-2009
> > Physical Review Letters
> > Metamaterials could reduce friction in nanomachines
> > Nanoscale machines expected to have wide application in industry,
> > energy, medicine and other fields may someday operate far more
> > efficiently thanks to important theoretical discoveries concerning
> > the manipulation of famous Casimir forces that took place at the US
> > Department of Energy's Ames Laboratory.
> > US Department of Energy
> >
> > Contact: Mark Ingebretsen
> > ma...@ameslab.gov
> > 515-294-3474
> > DOE/Ames Laboratory
> > http://www.ameslab.gov/final/News/2009rel/Casimir.html
> >
> > Confession: I don't know enough to understand this.
>
> Hey, Dan, nice to hear from you! I had just been wondering if you'd
> dropped out of this group, hadn't seen your posts in a while.
For a while, I didn't have a home Internet connection. I now have one
again. It's erratic, but does usually stay up for hours at a time.
Thanks.
> I assume this is the same thing:
> http://www.technologyreview.com/blog/arxiv/24499/
>
> One thing I didn't really understand (after an admittedly cursory
> reading) was this. It still requires you to have just as big an
> energy source as with other methods of propulsion. It gets you out
> of having to carry around reaction mass, but as far as I can tell
> that just means you're satisfying conservation of momentum by
> emitting electromagnetic waves as your "exhaust." If that's the
> case, then how is it any better than simply propelling yourself
> using the reaction from a laser (which has got to be the world's
> crappiest imaginable method of propulsion)?
Ric Locke's explanation elsewhere in the thread might unconfuse you.
Eric Ammadon
>Eric Ammadon wrote:
>
>> "Dan Goodman" <dsg...@iphouse.com> wrote:
>>
>> > Public Release: 7-Dec-2009
>> > Physical Review Letters
>> > Metamaterials could reduce friction in nanomachines
>> > Nanoscale machines expected to have wide application in industry,
>> > energy, medicine and other fields may someday operate far more
>> > efficiently thanks to important theoretical discoveries concerning
>> > the manipulation of famous Casimir forces that took place at the US
>> > Department of Energy's Ames Laboratory.
>> > US Department of Energy
>> >
>> > Contact: Mark Ingebretsen
>> > ma...@ameslab.gov
>> > 515-294-3474
>> > DOE/Ames Laboratory
>> > http://www.ameslab.gov/final/News/2009rel/Casimir.html
>> >
>> > Confession: I don't know enough to understand this.
>>
>> "The Casimir effect was named after Dutch physicist Hendrik Casimir,
>> who postulated its existence in 1948."
>
>Yes, but what IS it?
I'd guess that it's prolly just about the same thing that causes
matter to remain stuck together on the molecular level, which likely
ain't too different from what makes molecules stick together on the
atomic level, and could have something to do with covalence or who
knows what other fancy properties. I don't know what Mr Casimir got
out of the deal but it seems like he should've at least gotten a pat
on the back for bothering to think and wonder about the differences
between the macro and micro. In summary, you should ask someone who
Knows, and that ain't me; Nikola Tesla could probably make sense of it
(though maybe not without bringing up the topic of disintegrator rays)
but he's way dead. <g>
James A. Donald
> > Hendrik Casimir, who postulated its existence in
> > 1948."
"Dan Goodman"
> Yes, but what IS it?
The vacuum energy density is reduced between two objects
that are close together, so the vacuum energy outside
pushes them together.
This leads to a number of enormous paradoxes and deep
unsolved problems in quantum theory, the big bang, the
anthropic principle, and cosmology, but is pretty well
understood when it comes to small things sticking
together.
Eric Ammadon
>The vacuum energy density is reduced between two objects
>that are close together, so the vacuum energy outside
>pushes them together.
Energy isn't a vector, and space can't get emptier than absolutely
empty, so how's that work again?
It's probably unfair to ask that, I really don't expect you to write
"Advanced Quantum Physics For Stupid Laymen" in one post.
Ric Locke
> I'd guess that it's prolly just about the same thing that causes
> matter to remain stuck together on the molecular level,
No. The bonding forces result from the exchange of electrons and are an
expression of the electroweak force (electronic + weak, the theories
merge at certain energy levels). Van der Waals forces, which cause
(among other things) friction, fall into the same category and may in
fact be the same thing looked at from another angle. The Casimir Effect
results from those forces changing the spacetime constants in their
close vicinity and is something quite different, not related to the
electroweak forces.
Regards,
Ric
Ric Locke
That's the "classical" explanation, which nowadays includes Einstein.
One of the goals, perhaps the Holy Grail, of modern physics is to marry
Einstein and Bohr (more properly, the successors to Bohr who worked out
quantum theory in more detail) so as to produce a set of equations that
encompasses both -- a "Theory of Everything". Quantum theory is
enormously more complex than classical, and contains a lot of
arbitrariness and apparent contradictions, which offends those theorists
who use "elegance" as a criterion, i.e. most of them.
Hawking and those who follow his general thrust have been trying to use
black holes, more precisely the event horizon of black holes, as a tool
to unscrew the inscrutable, and have had some success at it from a
theoretical point of view. His work, and that of those who follow that
thrust, has resulted in more contradictions. The correct ting to do when
your theory throws up zeroes, infinities, and contradictions is to do
experiments. They can't do experiments, though, because you can't order
a black hole from McMaster-Carr (and probably couldn't pay the shipping
charges if you could) or make one in the laboratory.
The quantum theory explanation of the Casimir Force is relatively new.
It works just as well as the classical one does in terms of prediction,
and an apparatus to measure and examine it is within the reach of the
average experimenter. This makes it a place where quantum and classical
theories intersect that doesn't involve visiting Cygnus-X, so it's
interesting (!) to both theoretical and experimental physicists.
Regards,
Ric
Sea Wasp (Ryk E. Spoor)
Quantum physics is sorta like Cthulhu; few can really understand it and
remain sane.
--
Sea Wasp
/^\
;;;
Live Journal: http://seawasp.livejournal.com
Eric Ammadon
Yeah, I'm gonna need to let you intelleckshuls figger out all that
stuff about "changing constants", cause in my lexicon those constant
thingys are constant, that being what defines them and all.
Cosmologically speaking, it's time for me to refill the wood box, I
wouldn't want to run out of ammunition during tonight's session of
fire-pondering. <g>
Michael Stemper
>Have you ever wondered how the Tardis is bigger on the inside than on
>the outside? I have. One way to do that is that it isn't: the door into
>the tardis shrinks people and things as they go through, and enlarges
>them again on the way out...
>
>The real tardis does't do that, of course. It really is bigger on the
>inside.
I recently saw the early episode entitled "The Time Meddler". It's the
first one in which another Time Lord is portrayed. The meddler's TARDIS
worked exactly like that.
As an exercise in real analysis, I came up with a metric function
that enables the TARDIS to be bigger inside than it is outside.
--
Michael F. Stemper
#include <Standard_Disclaimer>
Always use apostrophe's and "quotation marks" properly.
Suzanne Blom
"Sea Wasp (Ryk E. Spoor)" <sea...@sgeinc.invalid.com> wrote in message
news:hfti44$u4k$2...@news.eternal-september.org...
> Eric Ammadon wrote:
>> James A. Donald <jam...@echeque.com> wrote:
>>
>>> The vacuum energy density is reduced between two objects that are close
>>> together, so the vacuum energy outside pushes them together.
>>
>> Energy isn't a vector, and space can't get emptier than absolutely
>> empty, so how's that work again?
>>
>> It's probably unfair to ask that, I really don't expect you to write
>> "Advanced Quantum Physics For Stupid Laymen" in one post.
>
> Quantum physics is sorta like Cthulhu; few can really understand it and
> remain sane.
>
what the result would be if we could somehow raise children in a world who
is quantum physical. Surely, at the minumum, they would all think we are
totally bonkers.
Eric Ammadon
>
>"Sea Wasp (Ryk E. Spoor)" <sea...@sgeinc.invalid.com> wrote in message
>news:hfti44$u4k$2...@news.eternal-september.org...
>> Eric Ammadon wrote:
>>> James A. Donald <jam...@echeque.com> wrote:
>>>
>>>> The vacuum energy density is reduced between two objects that are close
>>>> together, so the vacuum energy outside pushes them together.
>>>
>>> Energy isn't a vector, and space can't get emptier than absolutely
>>> empty, so how's that work again?
>>>
>>> It's probably unfair to ask that, I really don't expect you to write
>>> "Advanced Quantum Physics For Stupid Laymen" in one post.
>>
>> Quantum physics is sorta like Cthulhu; few can really understand it and
>> remain sane.
I put no great premium on 'sanity', but I do figure that in any model
where your constants have to be changeable, your formulas are way
screwed up.
>And I am one of those who occasionally thinks it would be interesting to see
>what the result would be if we could somehow raise children in a world who
>is quantum physical. Surely, at the minumum, they would all think we are
>totally bonkers.
Yours don't, already? How'd you work that?
Joel Polowin
> The correct ting to do when
> your theory throws up zeroes, infinities, and contradictions is to do
> experiments. They can't do experiments, though, because you can't order
> a black hole from McMaster-Carr (and probably couldn't pay the shipping
> charges if you could) or make one in the laboratory.
"Okay, it turns out that the LHC is, in fact, generating micro black
holes.
The *good* news is that we can do some experiments to test the
Casimir theories. The *bad* news is... we've probably only got a
few months to do the experiments..."
JF
> changing the spacetime constants
err.... <holds up hand>
JF
Ric Locke
Well, of course if Hawking is correct the only real hazard is to the
folks near the target structure. Not even the LHC can pour enough energy
into the system to create anything but a microgram-sized or smaller
black hole, and those should have lives measured in picoseconds or
shorter. The Hawking radiation emitted as they decay could be hazardous
to the health of bystanders.
Should be interesting.
I was just trying to visualize the catalogue page. "SPECIAL NOTE:
Hazardous materials handling charges apply. Singularities with
Schwartshild radius one millimeter and larger cannot be delivered within
the heliopause without EPA clearance; submit form EP-3079B (amended) in
triplicate with order..."
Regards,
Ric
Ric Locke
Yup. Can't do the math myself, you understand, but the presence of
masses changes otherwise-constant values in the equations, which results
in a smaller vacuum energy. That's the whole basis of the classical
explanation of the Casimir effect.
Regards,
Ric
Ric Locke
"Your father will hear of this, young man. It's not /nice/ to distort
the space-time continuum!"
"Awwww... I didn't /mean/ to."
James A. Donald
wrote:
> James A. Donald <jam...@echeque.com> wrote:
>
> >The vacuum energy density is reduced between two objects
> >that are close together, so the vacuum energy outside
> >pushes them together.
>
> Energy isn't a vector, and space can't get emptier than absolutely
> empty, so how's that work again?
Space can get emptier than absolutely empty, and the derivative of the
energy density is a vector.
Eric Ammadon
Well that's the thing of it, if your constants can't remain constant,
your formulas contain some sort of fallacy and need to be replaced by
some other set of formulas (ae?) having only constant constants.
The fact that the idea of "changing constants" is accepted may be an
indication that it is part of that TRVTH you mentioned in another
post. Experiments that are touted as "proof" of something like this
may prove something, but not necessarily what people find it most
convenient to believe that they prove.
Eric Ammadon
>On Fri, 11 Dec 2009 03:44:30 -0700, Eric Ammadon <n...@spam.thankee>
>wrote:
>
>> James A. Donald <jam...@echeque.com> wrote:
>>
>> >The vacuum energy density is reduced between two objects
>> >that are close together, so the vacuum energy outside
>> >pushes them together.
>>
>> Energy isn't a vector, and space can't get emptier than absolutely
>> empty, so how's that work again?
>
>Space can get emptier than absolutely empty,
That statement is so obviously stupid that I'm amazed.
Michelle Bottorff
> >Space can get emptier than absolutely empty,
>
> That statement is so obviously stupid that I'm amazed.
Welcome to quantum physics.
The entire field is made up of stuff that makes no sense at all.
But it's *mathematically* sound.
It's perfectly possible to work out the math for "emptier than
absolutely empty" you know. That's what those little '-' signs are for.
And when they stop goggling and going "But... but... that's impossible!"
and start trying to figure out ways to test it out...
the tests *work*.
Apparently the unverse doesn't particularly care whether it makes sense
or not.
--
Michelle Bottorff -> Chelle B. -> Shelby
L. Shelby, Writer http://www.lshelby.com/
Livejournal http://lavenderbard.livejournal.com/
rec.arts.sf.composition FAQ http://www.lshelby.com/rasfcFAQ.html
Ric Locke
No. It's a matter of misused language, like "law" for physical realities
such as gravity. Calling gravity a "law" tends to imply that some
legislature enacted it, and that it could be repealed. Neither is the
case (and IMO it is a pernicious overcompliment to legislatures,
Princes, and other "lawmakers"), but the usage persists.
"Constants" is another such misuse. It's short for "constants of
proportionality", the ratios between the various components, not the
standalone word meaning "fixed" or "immutable". A better word might be
"coefficients".
It is a fundamental concept in modern, post-Einstein physics that
spacetime is different depending on where it is measured. Gravity is a
change in spacetime, analogized as "curvature". In that light it isn't a
surprise that the coefficients change under different conditions. The
people who originally observed and/or calculated them described them as
"constants" because they didn't understand that, and the usage persists.
Science does not concern itself with "truth" let alone TRVTH; it leaves
the former for the philosophers and the latter for the theologians, and
contents itself with usability in the sense of reproducibility -- the
Sun shines on the evil and the good alike, the rain falls on the just
and the unjust, and science examines the sun and the rain, not the good
and the unjust. Calling the result of an experiment "proof" is another
sloppy use of language, like "law" and "constant". All a properly framed
and executed experiment "proves" is that either (a) the result will be
constant regardless of personalities, or (b) the theory that informed
the framing and execution of it is faulty. Experience demonstrates that
(b) is almost invariable, but there is enough (a) component to shrug and
say, "Close enough. The next guy can get a few more decimal places."
Regards,
Ric
Ric Locke
> James A. Donald <jam...@echeque.com> wrote:
>
>>On Fri, 11 Dec 2009 03:44:30 -0700, Eric Ammadon <n...@spam.thankee>
>>wrote:
>>
>>> James A. Donald <jam...@echeque.com> wrote:
>>>
>>> >The vacuum energy density is reduced between two objects
>>> >that are close together, so the vacuum energy outside
>>> >pushes them together.
>>>
>>> Energy isn't a vector, and space can't get emptier than absolutely
>>> empty, so how's that work again?
>>
>>Space can get emptier than absolutely empty,
>
> That statement is so obviously stupid that I'm amazed.
No. Your reaction to it proves that you don't understand the subject.
The existence of the Casimir Effect establishes that under the
formulation in which the words (rather than the underlying math) make
any sense, space can be "emptier than empty" -- that's the /point/ and
the reason Casimir is remembered. Disagreeing with the verbal analogy,
which is deficient by definition (and James knows that), is pointless.
Regards,
Ric
Eric Ammadon
I'd call gravity a property, or an operating characteristic, but
that's just my lexicon. Usage does usually prevail, for good or ill.
Language is a huge issue, perhaps one of the largest issues involved
since arriving at conclusions reproducible by independent
experimentors requires that what is to be reproduced must be clearly
and precisely communicable.
But as language and its inherent invitations to sloppiness add
difficulty, it can also point out issues.
>"Constants" is another such misuse. It's short for "constants of
>proportionality", the ratios between the various components, not the
>standalone word meaning "fixed" or "immutable". A better word might be
>"coefficients".
The language issues surrounding what you've expressed there prevent me
from making a valid response. (I'm not kidding here.)
>It is a fundamental concept in modern, post-Einstein physics that
>spacetime is different depending on where it is measured.
Then it almost certainly isn't actually "spacetime", but instead is
something else, a combination of multiple characteristics, each of
which *is* the same everywhere, but which give the composite different
characteristics based on circumstance. (I hope you're able to
decipher that sentence.) If it is assumed that "space" and "time" are
both the same everywhere, that implies that what we call "spacetime"
contains at least one additional component that is not properly
accounted for and thus requires "special casing".
> Gravity is a
>change in spacetime, analogized as "curvature". In that light it isn't a
>surprise that the coefficients change under different conditions. The
>people who originally observed and/or calculated them described them as
>"constants" because they didn't understand that, and the usage persists.
>
>Science does not concern itself with "truth" let alone TRVTH; it leaves
>the former for the philosophers and the latter for the theologians, and
>contents itself with usability in the sense of reproducibility -- the
>Sun shines on the evil and the good alike, the rain falls on the just
>and the unjust, and science examines the sun and the rain, not the good
>and the unjust. Calling the result of an experiment "proof" is another
>sloppy use of language, like "law" and "constant". All a properly framed
>and executed experiment "proves" is that either (a) the result will be
>constant regardless of personalities, or (b) the theory that informed
>the framing and execution of it is faulty. Experience demonstrates that
>(b) is almost invariable, but there is enough (a) component to shrug and
>say, "Close enough. The next guy can get a few more decimal places."
No fight, no blame.
Eric Ammadon
If space can be emptier than empty, then empty is not really empty and
ought to be recognized as non-empty.
Gerry Quinn
n...@spam.thankee says...
But then again, you think that Newton was trolling when he invented his
laws of dynamics...
However, it might have been better expressed as "space can get emptier
than what we call usually call empty".
In this context, it is useful to think of the vacuum in similar terms
to what used to be called the aether; it fills the universe and all
mass and energy as we usually understand them are fundamentally no more
than its vibrations. In certain configurations, its local energy
density can become less than that associated with regions of space that
are not perturbed by nearby matter.
- Gerry Quinn
Ric Locke
Bah. It's an analogy, "analogy" taken as a superset of "metaphor",
"simile", and related concepts. I know, and the people who originated it
know, that like any other analogy it has deficiencies. We're dealing
with some abstruse stuff here, and rather than picking the analogy apart
(which is what you spend most of your arguments doing) it's more
profitable to try to figure out why somebody thought it was a useful
analogy and work back from that.
For instance: Particles aren't picoscopic billiard balls. They are
things that have some characteristics analogous to billiard balls, and
"things" in that sentence is also an analogy (consider the
not-entirely-serious proposal that there's only one electron in the
Universe; what we see is it traveling backward and forward in time. It
would at least explain why they're all alike!) "Particles" also have a
long list of characteristics that are not analogous to those of billiard
balls -- and the person using the "billiard ball" analogy almost
certainly knows that, and considers that in the situation being
discussed the analogy is useful (not "true"), whether or not it is also
useful in some other situation.
The same occurs throughout any attempt by laymen to get some notion of
what the physicists and other scientists are on about. Concentrate on
why the person doing the explaining thought the analogy might be useful
in that line of discourse, rather than arguing against /the analogy/,
and you might get somewhere. The alternative is trying to have sex with
"...the girl wearin' nothin' but a smile an' a towel in the picture on
the billboard by the big ol' highway", i.e. masturbation-equivalent.
Regards,
Ric
Suzanne Blom
"Eric Ammadon" <n...@spam.thankee> wrote in message
news:f587i59s3sj699a3r...@4ax.com...
my pockets are empty, gives up, and goes away in disgust. I reach into my
pocket and pull out my lucky wooden nickel and give it a thinkful pat. Was
the holdup man wrong when he decided my pockets were empty? No, in his
frame of reference, my pockets were empty. Now that I've taken out the
lucky piece are my pockets empty? Well, again, it depends. They do, after
all, have some lint and some of that perfume from the laundry detergent
coats the threads and like that.
Again, back in the 1600's when people were deciding where the constellation
lines should be drawn, there was this star that they named 10 Ursa Major.
10 UMa has now drifted into the constellation of Lynx. In this case, people
have quietly started calling it by other names, but in some cases it's
really hard to change the name or in the given field the meanings of the
word/name has changed with the understanding of what's happening. This does
make wandering into any field difficult. From football to physics, word
names do not mean to an insider what they would to a naive outsider.
Eric Ammadon
Ben Crowell
>One thing I didn't really understand (after an admittedly cursory
>reading) was this. It still requires you to have just as big an
>energy source as with other methods of propulsion. It gets you out
>of having to carry around reaction mass, but as far as I can tell
>that just means you're satisfying conservation of momentum by
>emitting electromagnetic waves as your "exhaust." If that's the
>case, then how is it any better than simply propelling yourself
>using the reaction from a laser (which has got to be the world's
>crappiest imaginable method of propulsion)?
Rick Locke wrote:
>No, Ben, it's more analogous to a screw propeller, an airplane or ship.
>Grab (virtual) particles and shove them aft before they go away, and you
>get a change of momentum.
I understand that. The problem is that the virtual particles have
zero rest mass, which means that the power-to-thrust ratio is the
same as for a laser. For an exhaust composed of material particles
at nonrelativistic exhaust velocity v, the power-to-thrust ratio is
P/F = v/2 .
For an exhaust composed of particles with zero rest mass, it's
P/F = c ,
which is less favorable by many, many orders of magnitude. In
general, a high exhaust velocity is better in terms of requiring
you to bring along less reaction mass, but worse in terms of energy
requirements. A laser represents a certain extreme choice of
exhaust velocity, which may or may not be optimal for a given
application. But AFAICT the Casimir force represents exactly the
same engineering trade-off as a laser, so it's not clear to me why
anyone would care. Why not just use a laser?
Brian M. Scott
<warric...@gmail.com> wrote in
<news:yywlfuaq8s8x$.y929bft6...@40tude.net> in
rec.arts.sf.composition:
[...]
> For instance: Particles aren't picoscopic billiard balls.
You might even say that they're a lot hairier than billiard
balls!
[...]
Brian
Brian M. Scott
<sue...@execpc.com> wrote in
<news:pOudnZyikbngVr7W...@posted.localnet> in
rec.arts.sf.composition:
[...]
> a thinkful pat.
I really like that one!
[...]
Brian
Eric Ammadon
>Bah.
Bah yourself.
> It's an analogy, "analogy" taken as a superset of "metaphor",
>"simile", and related concepts. I know, and the people who originated it
>know, that like any other analogy it has deficiencies.
The very need to draw deficient analogies is evidence that a thing is
not fully understood; was it truly understood, analogies would be
unnecessary.
If you claim to understand "Casimir force" feel free to explain its
operation without the use of analogies.
If you claim that deficient analogies are acceptable, you should then
find it reasonable to explain the combustibility of materials as being
analogous to their phlogiston content.
I am weary of scientific TRVTH. I know very little, but among those
few things is the knowledge that much of the information that had to
be regurgitated to obtain an engineering degree was as solid as swiss
cheese.
The fact that theories can be concocted to fit special cases does not
evidence understanding of what lies behind the data, only that the
data fits the formula.
You like deficient analogies? Here's one, then. Science looks at the
words "hemoglobin" and "hematoma" then derives a formula saying that
if the first 3 letters of a word are "hem" it means "blood", the
formula is verified by a few others, an article is printed, and a new
TRVTH is blessed; it works fine for the two special cases in question,
but beyond that it's useless.
What priests of scientific TRVTH are unwilling to admit is that their
TRVTH is limited. Special cases exist, but they describe only parts
of the general case.
Occasionally an intellekshul will have the honesty to actually attempt
to write a description free from analogies. Usually when that occurs
the well-meaning individual will be forced to give up quickly, and
rather than admit that although science can accomplish much it knows
little, they usually put their backs against their TRVTH and fight
like cornered rats.
I know that I am alive, the world exists, I have free-will, and my
free-will has an effect; beyond that I'm still gathering data.
Have a nice day, and don't drink too much phlogiston or you might
spontaneously combust. And do keep in mind that if science understood
the theory-of-everything there would be no need for physics,
chemistry, so forth, and so on, because all those areas that are
currently considered essential are small parts of everything.
Ric Locke
> Ric Locke <warric...@gmail.com> wrote:
>
>>Bah.
>
> Bah yourself.
>
>> It's an analogy, "analogy" taken as a superset of "metaphor",
>>"simile", and related concepts. I know, and the people who originated it
>>know, that like any other analogy it has deficiencies.
>
> The very need to draw deficient analogies is evidence that a thing is
> not fully understood; was it truly understood, analogies would be
> unnecessary.
Bullshit. Both understanding and a language containing the concepts are
necessary. The first is easier than the second, which is why scientists
borrow and appropriate terms and use analogies. Even mathematics, the
so-called "language of science", is simulation -- metaphor -- rather
than the thing itself.
In your terms, no explanation of /anything/ is possible, since the only
"real" explanation is the thing itself. That may even be true, but it
isn't /useful/.
>
> If you claim to understand "Casimir force" feel free to explain its
> operation without the use of analogies.
Space contains energy, even "empty" space. We perceive space as empty
because we are only equipped to perceive the effects of energy flows,
not energy or even energy flow directly, and since the energy of space
is uniform there is no flow and we don't detect a change.
Matter distorts space. One of the ways it does so is by reducing the
energy level of nearby space.
If you place two masses in close proximity, the energy of space is
reduced in the narrow gap. There is then an energy imbalance between the
space between the masses and the remainder of space. An energy imbalance
results in a flow of energy from the higher-level place to the
lower-energy one. We perceive that flow as a force that pushes the two
masses closer together. That force is called the "Casimir force" or
"Casimir effect", after the fellow who first suggested it and
demonstrated by experiment that it exists.
There -- and yet I failed utterly: "force", "mass", "space", "energy",
"flow" (in this context), "higher" and "lower" (again in this context),
"distort", and several of the other words are /metaphors/ that
substitute some more nearly familiar concept for one that no word exists
to describe. Go further: /All/ the words are metaphors in one sense or
another; the map is not the territory; the name is not the thing named.
By the standard you insist on, communication is impossible. Again, that
may be true, but it isn't a useful assumption or concept.
>
> If you claim that deficient analogies are acceptable, you should then
> find it reasonable to explain the combustibility of materials as being
> analogous to their phlogiston content.
Nope. "Phlogiston" is not a useful concept; it predicts things that
don't happen, and fails to predict things that do happen. It is not a
good enough metaphor to serve as an explanation.
>
> I am weary of scientific TRVTH. I know very little, but among those
> few things is the knowledge that much of the information that had to
> be regurgitated to obtain an engineering degree was as solid as swiss
> cheese.
You and me both. The conundrum is solved thuswise: If it's TRVTH it's
religion. The only thing science requires is that it be /useful/ in some
sense.
>
> The fact that theories can be concocted to fit special cases does not
> evidence understanding of what lies behind the data, only that the
> data fits the formula.
>
> You like deficient analogies? Here's one, then. Science looks at the
> words "hemoglobin" and "hematoma" then derives a formula saying that
> if the first 3 letters of a word are "hem" it means "blood", the
> formula is verified by a few others, an article is printed, and a new
> TRVTH is blessed; it works fine for the two special cases in question,
> but beyond that it's useless.
Bullshit. Both words come from the word for "blood" in a predecessor
language -- Greek, I believe -- just as "blood" comes from German. One
is a component of blood, the other contains blood. You demand that the
only valid name is the thing itself, and that's unwieldy (at least). It
is far easier to say "hemoglobin" than to list a long protein-chain
formula, plus structure information including the iron atom in the
middle. No TRVTH involved, just a convenient linguistic shortcut.
>
> What priests of scientific TRVTH are unwilling to admit is that their
> TRVTH is limited. Special cases exist, but they describe only parts
> of the general case.
I know of no scientist who makes that claim. In fact, the only person
more than ten meters from a religious altar who I have ever heard making
that claim is you. That is especially true in physics. The existence of
a search for a "Theory of Everything" is an implicit acknowledgement
that existing explanations are only partial.
>
> Occasionally an intellekshul will have the honesty to actually attempt
> to write a description free from analogies. Usually when that occurs
> the well-meaning individual will be forced to give up quickly, and
> rather than admit that although science can accomplish much it knows
> little, they usually put their backs against their TRVTH and fight
> like cornered rats.
Bullshit. "Occasionally", "an", "intellectual", "description", "free",
"from", "analogy", and all the other words are analogies, metaphors
twice removed -- there is the thing itself, whatever it might be; there
is your perception of it; and there is the symbol you emit to represent
your perception of whatever it is.
In effect, you are demanding that things be explained to you in words
you have already connected to your perception of things, and that you
not be required to make any new perceptual connections in order to
receive and use the explanations. That isn't possible. It isn't even
desirable.
>
> I know that I am alive, the world exists, I have free-will, and my
> free-will has an effect; beyond that I'm still gathering data.
It's a start.
>
> Have a nice day, and don't drink too much phlogiston or you might
> spontaneously combust. And do keep in mind that if science understood
> the theory-of-everything there would be no need for physics,
> chemistry, so forth, and so on, because all those areas that are
> currently considered essential are small parts of everything.
Ah. And incremental approximations aren't good enough -- it has to be
the full understanding or none exists. Again, bullshit. How many hairs
on your head? Exact values, now, estimates and approximations aren't
good enough, remember.
Regards,
Ric
alie...@gmail.com
The proposed device would be completely electromagnetic, meaning no
tanks containing expensive, volatile, irreplaceable-once-used fuel.
Solar cells would serve as an on-board fuel replacement system.
The device would need no complex, fragile optical system.
Also, virtual particles need not be massless AFAICT; the difference
is that massless virtual particle effects have infinite range but
massive ones' range will be inversely proportional to their mass. That
should improve their thrust.
Finally, it would have no blinding, searing exhaust like a laser. In
fact it would have no exhaust at all.
What good is that? Ignoring SF stealth apps for the moment, it won't
barbecue anything behind it when it's providing thrust.
Mark L. Fergerson
Ric Locke
> I wrote:
> >One thing I didn't really understand (after an admittedly cursory
> >reading) was this. It still requires you to have just as big an
> >energy source as with other methods of propulsion. It gets you out
> >of having to carry around reaction mass, but as far as I can tell
> >that just means you're satisfying conservation of momentum by
> >emitting electromagnetic waves as your "exhaust." If that's the
> >case, then how is it any better than simply propelling yourself
> >using the reaction from a laser (which has got to be the world's
> >crappiest imaginable method of propulsion)?
>
> Rick Locke wrote:
> >No, Ben, it's more analogous to a screw propeller, an airplane or ship.
> >Grab (virtual) particles and shove them aft before they go away, and you
> >get a change of momentum.
>
> I understand that. The problem is that the virtual particles have
> zero rest mass
Who told you that? Go find him or her and strike smartly, with a stick
no larger than your thumb. The only thing with zero rest mass is the
photon, and that's actually one of those metaphors Eric so despises. In
our frame of reference, photons are defined as moving at the speed of
light; if it's "at rest" it isn't a photon.
Virtual particles have zero net ENERGY because they come in
matter-antimatter pairs (another oversimplified metaphor), and
annihilate one another before the rest of the Universe notices and
starts grumbling and issuing summonses about conservation laws. A
virtual electron, proton, etc. has the same mass as a "permanent" one;
it just doesn't last any significant time. If you can grab one and move
it before it evaporates, you will get momentum exchange just like you do
when your propeller grabs an air molecule and accelerates it.
This is not to say that grabbing virtual particles is /possible/ -- it's
all speculation and handwaving at the moment. But your objection isn't a
valid one; in fact, it's the opposite of what the article describes.
>, which means that the power-to-thrust ratio is the
> same as for a laser. For an exhaust composed of material particles
> at nonrelativistic exhaust velocity v, the power-to-thrust ratio is
> P/F = v/2 .
> For an exhaust composed of particles with zero rest mass, it's
> P/F = c ,
> which is less favorable by many, many orders of magnitude. In
> general, a high exhaust velocity is better in terms of requiring
> you to bring along less reaction mass, but worse in terms of energy
> requirements. A laser represents a certain extreme choice of
> exhaust velocity, which may or may not be optimal for a given
> application. But AFAICT the Casimir force represents exactly the
> same engineering trade-off as a laser, so it's not clear to me why
> anyone would care. Why not just use a laser?
Right. For efficiency you give massive things a low acceleration; a
laser goes the other direction -- a "photon drive" is as inefficient as
possible. The quantum-mechanical explanation of the Casimir Effect gives
you mass to play with, which makes your drive more efficient.
Regards,
Ric
Luke Campbell
<crowel...@lightSPAMandISmatterEVIL.com> wrote:
> I understand that. The problem is that the virtual particles have
> zero rest mass, which means that the power-to-thrust ratio is the
> same as for a laser.
Speaking as someone who has actually done quantum electrodynamic
calculations for my job, I can say that virtual particles can have any
rest mass. The rest mass[1] is found by E^2/c^4 - p^2/c^2 where p is
the particle momentum, E is the particle energy, and c is the speed of
light. For virtual particles, which act to exchange forces between
real particles, E and p can be anything subject only to the constraint
that momentum and energy in the total interaction is conserved. A
real photon always has zero rest mass, a virtual photon can have a
positive or even a negative rest mass. Not to mention that you can
also get virtual electrons, which again do not need to have a rest
mass equal to the electron rest mass we are all familiar with.
That said, the idea that these Casimir-like forces will lead to
anything like a reactionless drive is flawed. Quantum mechanics
strictly conserves energy and momentum. Any properly constructed
model based on quantum mechanics will also conserve energy and
momentum. That means that these Casimir-like forces must arise from
an exchange of momentum with something else. My guess is that they
end up applying a force to some other nearby object, but it may be
that they create real particles which carry away the momentum.
Virtual particles only act to couple real objects, so virtual
particles cannot carry away the momentum - once you get to the point
that the separation between the interacting particles becomes large
[2], your virtual particles become real particles.
[1] Rest mass can seem an odd term to apply to ephemeral fluctuations
of things that don't really exist. Invariant mass might be a better
term to use.
[2] Large in the sense that the uncertainty relation is not violated -
you need dx dp < h-bar/2. dx in this case is the separation between
the interacting particles. dp is how much the momentum would differ
from a real particle. As the separation grows, the particle becomes
more and more real.
Luke
Tim Little
> http://www.technologyreview.com/blog/arxiv/24499/
>
> One thing I didn't really understand (after an admittedly cursory
> reading) was this. It still requires you to have just as big an
> energy source as with other methods of propulsion.
It's not a method of propulsion, really. It's perhaps better thought
of as a way of hiding microscopic amounts of momentum.
For example, using their figures a flipped 1 nm particle of the most
suitable material we know of could acquire about 0.0000002 m/s of
velocity. If flipped back, that velocity is cancelled.
The effect scales with the inverse fourth power of particle size, but
we're just not going to get particles much smaller than 1 nm with the
required electromagnetic property. Now perhaps if femtoengineering
were possible, this could be useful. At 10^-13 m or so (assuming the
magnetic properties would not be reduced corespondingly) the effect
could theoretically give sizeable delta-Vs.
> It gets you out of having to carry around reaction mass, but as far
> as I can tell that just means you're satisfying conservation of
> momentum by emitting electromagnetic waves as your "exhaust."
It's both more interesting than that and less useful.
It is more interesting in the respect that just as there can be
considered a vacuum energy, which in the Casimir effect is lowered by
excluding certain modes, certain types of magnetic properties
correspond to vacuum *momentum*. So changing the configuration allows
you to dump momentum into the vacuum. You could theoretically have a
stationary "black box" in vacuum that starts moving by itself (very
very slowly).
It is less useful in that you can't cycle it: returning to the
starting configuration brings the momentum back.
- Tim
Eric Ammadon
>On Sat, 12 Dec 2009 14:56:40 -0700, Eric Ammadon wrote:
>
>> Ric Locke <warric...@gmail.com> wrote:
>>
>>>Bah.
>>
>> Bah yourself.
>>
>>> It's an analogy, "analogy" taken as a superset of "metaphor",
>>>"simile", and related concepts. I know, and the people who originated it
>>>know, that like any other analogy it has deficiencies.
>>
>> The very need to draw deficient analogies is evidence that a thing is
>> not fully understood; was it truly understood, analogies would be
>> unnecessary.
>
>Bullshit.
We're done talking, pal. Welcome to my killfile.
Eric Ammadon
>A mundane analogy. Suppose a holdup man tries to mug me, and discovers that
>my pockets are empty, gives up, and goes away in disgust. I reach into my
>pocket and pull out my lucky wooden nickel and give it a thinkful pat. Was
>the holdup man wrong when he decided my pockets were empty? No, in his
>frame of reference, my pockets were empty. Now that I've taken out the
>lucky piece are my pockets empty? Well, again, it depends. They do, after
>all, have some lint and some of that perfume from the laundry detergent
>coats the threads and like that.
Most people believe that in order to remove something from their
pocket it must first have been placed there by mundane means. Having
never experienced anything inexplicable using the set of explanations
they were given as a child, they have no reason to question them.
>Again, back in the 1600's when people were deciding where the constellation
>lines should be drawn, there was this star that they named 10 Ursa Major.
>10 UMa has now drifted into the constellation of Lynx. In this case, people
>have quietly started calling it by other names, but in some cases it's
>really hard to change the name or in the given field the meanings of the
>word/name has changed with the understanding of what's happening. This does
>make wandering into any field difficult. From football to physics, word
>names do not mean to an insider what they would to a naive outsider.
The fact that 10 Uma appears to us to have drifted into Lynx does not
by itself mean that it has changed position, any more than the fact
that the sun rises and sets means that it circles the earth. I assume
that you realize that, and you are using it as an example because you
think I am an idiot.
It is easy to believe that we know things, yet it is difficult to know
the difference between what we know and what we believe.
Once upon a time I believed as others do, that what I had been taught
was true and correct. Then one day, at a time when what I had been
taught had led me into poverty, my truck was low on gas.
I pulled into the station beside a pump. I removed the gas cap, and
knowing that I had little money, I checked my wallet so I would know
when to stop the pump.
There was nothing there except a lone $20 bill. I realized that there
would be little left after filling the tank.
The pump stopped at $17 and change, the tank would accept no more
gasoline. I shrugged thinking it would be a thin week indeed, and put
the pump hose back and the gas cap on.
Inside the station the attendant quoted the amount as I had seen it on
the gas pump. I opened my wallet and gave him the $50 bill that was
there, somewhat surprised, concluding that there would be some
previously unexpected expenses in the days that followed.
There were indeed about $30 of unexpected expenses, and no, it was not
my first experience with the inexplicable, and no, I did not mistake
the denomination of the bill.
I have had reason to question what I was taught as a child and what I
was taught as an engineering student. Having discarded what was
clearly tainted, I found little remaining. The years since have been
lived in a wonderland, a world where fantasy's wildest imaginings are
tepid by comparison, a world of contentment and plenty.
I still find it surprising, and sad, that here in a newsgroup
supposedly devoted to the writing of novels about fantasy, magic, and
science-fiction, the belief that only what is placed in a pocket by
mundane means can be removed from it. So it goes.
R.L.
> Eric Ammadon <n...@spam.thankee> wrote:
>
>>>Space can get emptier than absolutely empty,
>>
>> That statement is so obviously stupid that I'm amazed.
>
> Welcome to quantum physics.
>
> The entire field is made up of stuff that makes no sense at all.
>
> But it's *mathematically* sound.
>
> It's perfectly possible to work out the math for "emptier than
> absolutely empty" you know. That's what those little '-' signs are for.
As in 'less than nothing'? -1?
What's hard about that?
R.L.
Eric Ammadon
>On Sat, 12 Dec 2009 08:03:32 -0500, Michelle Bottorff wrote:
>
>> Eric Ammadon <n...@spam.thankee> wrote:
>>
>>>>Space can get emptier than absolutely empty,
>>>
>>> That statement is so obviously stupid that I'm amazed.
>>
>> Welcome to quantum physics.
Odd, I didn't see Michelle's response, but I see your response to her
response.
>> The entire field is made up of stuff that makes no sense at all.
>>
>> But it's *mathematically* sound.
Ever witness a good con-man working the change-con?
>> It's perfectly possible to work out the math for "emptier than
>> absolutely empty" you know. That's what those little '-' signs are for.
>
>
>As in 'less than nothing'? -1?
>
>What's hard about that?
Show me an actual -1, not a "borrowed" one, not a conceptual thing you
can use but not touch, and we'll talk.
Michelle Bottorff
> >> Welcome to quantum physics.
>
> Odd, I didn't see Michelle's response, but I see your response to her
> response.
The part of my post that wasn't quoted...
Ben Crowell
> On Sat, 12 Dec 2009 11:48:20 -0800, Ben Crowell wrote:
>
>> I wrote:
>> >One thing I didn't really understand (after an admittedly cursory
>> >reading) was this. It still requires you to have just as big an
>> >energy source as with other methods of propulsion. It gets you out
>> >of having to carry around reaction mass, but as far as I can tell
>> >that just means you're satisfying conservation of momentum by
>> >emitting electromagnetic waves as your "exhaust." If that's the
>> >case, then how is it any better than simply propelling yourself
>> >using the reaction from a laser (which has got to be the world's
>> >crappiest imaginable method of propulsion)?
>>
>> Rick Locke wrote:
>> >No, Ben, it's more analogous to a screw propeller, an airplane or ship.
>> >Grab (virtual) particles and shove them aft before they go away, and you
>> >get a change of momentum.
>>
>> I understand that. The problem is that the virtual particles have
>> zero rest mass
>
> Who told you that? Go find him or her and strike smartly, with a stick
> no larger than your thumb.
Maybe you didn't look at the link I provided? Here it is again:
http://www.technologyreview.com/blog/arxiv/24499/
If you want more technical details, here is the paper it is referring
to:
http://arxiv.org/abs/0912.1031
The abstract clearly states that the effect involves electromagnetic
virtual particles. Note the word "the" in my quoted text above,
"the virtual particles have zero rest mass," which makes it clear that
I'm not stating as a general proposition that all virtual particles
in general have zero rest mass.
> The only thing with zero rest mass is the
> photon, and that's actually one of those metaphors Eric so despises. In
> our frame of reference, photons are defined as moving at the speed of
> light; if it's "at rest" it isn't a photon.
The term "rest mass" is defined here:
http://en.wikipedia.org/wiki/Rest_mass
It doesn't imply that the particle is at rest.
Not to come off all high and mighty on you, Rick, but I do have a PhD
in physics. Your tone is also a little incongruous with the fact that
you're making some elementary mistakes.
Dan Goodman
> "Dan Goodman" <dsg...@iphouse.com> wrote:
>
> > Eric Ammadon wrote:
> >
> >> "Dan Goodman" <dsg...@iphouse.com> wrote:
> >>
> >> > Public Release: 7-Dec-2009
> >> > Physical Review Letters
> >> > Metamaterials could reduce friction in nanomachines
> >> > Nanoscale machines expected to have wide application in industry,
> >> > energy, medicine and other fields may someday operate far more
> >> > efficiently thanks to important theoretical discoveries
> concerning >> > the manipulation of famous Casimir forces that took
> place at the US >> > Department of Energy's Ames Laboratory.
> >> > US Department of Energy
> >> >
> >> > Contact: Mark Ingebretsen
> >> > ma...@ameslab.gov
> >> > 515-294-3474
> >> > DOE/Ames Laboratory
> >> > http://www.ameslab.gov/final/News/2009rel/Casimir.html
> >> >
> >> > Confession: I don't know enough to understand this.
> >>
> >> "The Casimir effect was named after Dutch physicist Hendrik
> Casimir, >> who postulated its existence in 1948."
> >
> > Yes, but what IS it?
>
> I'd guess that it's prolly just about the same thing that causes
> matter to remain stuck together on the molecular level, which likely
> ain't too different from what makes molecules stick together on the
> atomic level, and could have something to do with covalence or who
> knows what other fancy properties. I don't know what Mr Casimir got
> out of the deal but it seems like he should've at least gotten a pat
> on the back for bothering to think and wonder about the differences
> between the macro and micro. In summary, you should ask someone who
> Knows, and that ain't me; Nikola Tesla could probably make sense of it
> (though maybe not without bringing up the topic of disintegrator rays)
> but he's way dead. <g>
Thanks.
--
Dan Goodman
Journal at:
dsgood.livejournal.com
dsgood.dreamwidth.org
dsgood.insanejournal.com
Ben Crowell
But the same is true of a laser.
> The device would need no complex, fragile optical system.
This might make sense, although I think it's hard to say how complex
and fragile the hypothetical Casimir-force propulsion system would be,
since nobody knows how to build it.
> Also, virtual particles need not be massless AFAICT;
The authors of the paper describe it as using photons:
http://arxiv.org/abs/0912.1031
> Finally, it would have no blinding, searing exhaust like a laser. In
> fact it would have no exhaust at all.
I don't think this is correct. It would violate conservation of
momentum.
If you take a look at the actual paper, what they're describing isn't
really a blazing spaceship drive. They're describing an extremely
low-thrust system that could be used, for example, to control the
attitude of a satellite. They speculate about achieving delta-vees
of one micrometer per second (!), and state that even that would
require significant advances in technology.
Brian M. Scott
<warric...@gmail.com> wrote in
<news:veljksbc3fqj.1kf8srcktharm$.d...@40tude.net> in
rec.arts.sf.composition:
> On Sat, 12 Dec 2009 14:56:40 -0700, Eric Ammadon wrote:
[...]
>> You like deficient analogies? Here's one, then. Science
>> looks at the words "hemoglobin" and "hematoma" then
>> derives a formula saying that if the first 3 letters of
>> a word are "hem" it means "blood", the formula is
>> verified by a few others, an article is printed, and a
>> new TRVTH is blessed; it works fine for the two special
>> cases in question, but beyond that it's useless.
> Bullshit. Both words come from the word for "blood" in a
> predecessor language -- Greek, I believe --
Greek <ha�ma>, via modern Latin.
> just as "blood" comes from German.
No, <blood> is from Old English <bl�d>, from Proto-Germanic
*blo:dam 'blood', whence also Gothic <bl��>, Old Norse
<bl��>, Old High German <bluot>, and German <Blut>.
[...]
Brian
Ben Crowell
Thanks for your informative post. I think we can clear up some of
the uncertainty about the interpretation by looking at the paper:
http://arxiv.org/abs/0912.1031
First off, they describe it as an effect involving electromagnetic
fields, so the virtual particles we're talking about are definitely
photons. They also state:
It might also serve in the future as a "quantum wheel" to correct
satellite orientation in space.
So they're definitely not talking about pushing against some other
material object, and as you point out, this means that by conservation
of momentum, it must emit real particles. So it's a device
that emits real photons, which have zero rest mass.
Ben Crowell
to your post was based on a misinterpretation of the paper.
I originally interpreted it as:
(1) a way of transferring momentum to real particles.
You pointed out that it could also be interpreted as
(2) transferring momentum to some other material object via
virtual particles
(which is what would normally happen in the classic parallel-
plate capacitor version of the Casimir effect). But from Tim's
post, it sounds like it's actually:
(3) a way of transferring momentum to virtual particles
inside the device.
I think Tim is correct. I think the "vacuum" they're talking about
is not really a vacuum at all in the practical sense; when they talk
about transferring momentum to the vacuum, what they really mean is
that they're transferring momentum to the quantum fluctuations of
the vacuum that exists in the interior of the magneto-electric
particles. They show that the amount of momentum you can store in
such a particle is given by
p = (...)h/a ,
where (...) represents dimensionless constants, h is Planck's
constant, and a is the radius of the particle.
Ben Crowell
a second reply to Luke Campbell above pointing to your post, which
I think clears up some of the things he and I were getting wrong.
Tim Little wrote:
> The effect scales with the inverse fourth power of particle size, but
> we're just not going to get particles much smaller than 1 nm with the
> required electromagnetic property. Now perhaps if femtoengineering
> were possible, this could be useful. At 10^-13 m or so (assuming the
> magnetic properties would not be reduced corespondingly) the effect
> could theoretically give sizeable delta-Vs.
Hmm...well, 10^-13 m would be smaller than a hydrogen atom, but larger
than a nucleus. What is there that's in that size range? I guess you can
have things like muonic atoms, but those are unstable.
It might be more realistic to go down to the nuclear scale, 10^-15 m.
But then I don't think you get the right electromagnetic properties.
I don't know anything about the magneto-electric susceptibility, which
seems to be the relevant parameter, but in general it's a lot harder to
electrically polarize a nucleus than it is to polarize an atom.
Nuclei generally don't have intrinsic electric dipole moments. (It's
theoretically possible, if you have a nucleus with an octupole
deformation, but it's never actually been observed.) For a substance
without an intrinsic dipole moment, the electric susceptibility goes
like 1/(m \omega_o^2), where m is the mass and \omega_o is the
natural frequency of vibration. In the case of a nucleus, m is
thousands of times bigger than the mass of an electron, and
\hbar\omega_o for a giant dipole resonance is typically about 10
MeV, which is also very large compared to the frequency for
electrons. I think this is the fundamental reason why nobody ever
even talks about nuclear contributions to the polarizability
properties of matter.
Brian M. Scott
<n...@spam.thankee> wrote in
<news:co99i5930dg4l17bn...@4ax.com> in
rec.arts.sf.composition:
> "Suzanne Blom" <sue...@execpc.com> wrote:
>> A mundane analogy. Suppose a holdup man tries to mug me,
>> and discovers that my pockets are empty, gives up, and
>> goes away in disgust. I reach into my pocket and pull
>> out my lucky wooden nickel and give it a thinkful pat.
>> Was the holdup man wrong when he decided my pockets
>> were empty? No, in his frame of reference, my pockets
>> were empty. Now that I've taken out the lucky piece
>> are my pockets empty? Well, again, it depends. They
>> do, after all, have some lint and some of that perfume
>> from the laundry detergent coats the threads and like
>> that.
> Most people believe that in order to remove something from
> their pocket it must first have been placed there by
> mundane means. Having never experienced anything
> inexplicable using the set of explanations they were
> given as a child, they have no reason to question them.
None of this has any bearing on Suzanne's point.
>> Again, back in the 1600's when people were deciding where
>> the constellation lines should be drawn, there was this
>> star that they named 10 Ursa Major. 10 UMa has now
>> drifted into the constellation of Lynx. In this case,
>> people have quietly started calling it by other names,
>> but in some cases it's really hard to change the name
>> or in the given field the meanings of the word/name has
>> changed with the understanding of what's happening.
>> This does make wandering into any field difficult.
>> From football to physics, word names do not mean to an
>> insider what they would to a naive outsider.
> The fact that 10 Uma appears to us to have drifted into
> Lynx does not by itself mean that it has changed
> position, any more than the fact that the sun rises and
> sets means that it circles the earth. I assume that you
> realize that, and you are using it as an example because
> you think I am an idiot.
You're doing a good job of demonstrating it: apparently
you've altogether missed the (rather straightforward) point
of the example. Of course you *could* simply be avoiding
it; it wouldn't be the first time.
[...]
> There were indeed about $30 of unexpected expenses, and
> no, it was not my first experience with the inexplicable,
> and no, I did not mistake the denomination of the bill.
So you say. So, perhaps, you even believe.
[...]
> I still find it surprising, and sad, that here in a
> newsgroup supposedly devoted to the writing of novels
> about fantasy, magic, and science-fiction, the belief
> that only what is placed in a pocket by mundane means can
> be removed from it. So it goes.
No one actually expressed such a belief. Not that it really
matters: the idea that the writing of f/sf should be
associated with a loss of critical faculties is just
bizarre.
Brian M. Scott
<n...@spam.thankee> wrote in
<news:5d18i5tvf1kr42pcp...@4ax.com> in
rec.arts.sf.composition:
[...]
> The very need to draw deficient analogies is evidence that
> a thing is not fully understood; was it truly understood,
> analogies would be unnecessary.
There is some truth in this IF you limit yourself to
communication between people who already have the
understanding and the appropriate language in which to couch
it, though even then analogies can be useful, if only as
shorthand. If one party lacks the necessary language,
however, analogy is likely to be the only way in which the
knowledgeable party can convey any sense of the ideas
involved. In this case it's obvious that you, like most of
us, do lack the necessary language and are therefore in no
position to judge the understanding of others.
Tim Little
> They speculate about achieving delta-vees of one micrometer per
> second (!), and state that even that would require significant
> advances in technology.
For a 1-tonne satellite in Earth orbit, about the same delta-V as a
0.1 m^2 mirror reflecting sunlight for 20 minutes. Somewhat cheaper
than rustling up a tonne worth of 1 nm^3 nanoparticles and moving them
all individually.
- Tim
Tim Little
> material object, and as you point out, this means that by conservation
> of momentum, it must emit real particles. So it's a device
> that emits real photons, which have zero rest mass.
No, it (in theory) alters the momentum in the vacuum state, and
conservation of momentum requires that it be balanced by momentum of
the objects involved. Just like the Casimir effect alters the energy
in the vacuum, and that conservation law requires that it appear as a
material potential.
- Tim
Tim Little
> than a nucleus. What is there that's in that size range?
In a somewhat optimistic theory, perhaps something like stable
assemblies of strangelets. In practice it probably isn't even
possible.
> It might be more realistic to go down to the nuclear scale, 10^-15 m.
> But then I don't think you get the right electromagnetic properties.
Certainly not with ordinary nuclei, no - there is way too much
symmetry. That's why it would have to be artifically assembled
somehow (if that is even theoretically possible).
Then of course if we could play around with custom-building nuclear
matter, we would find delta-V of a few km/s to be rather trivial. So
it does seem to be a fundamentally poor proposition.
I suppose it's not really surprising: at any length scale l the
momentum effect is on the order of some fraction F of h/l (about 10^-7
with current materials), but manipulating at that scale typically
requires energy on the order of hc/l. So it's only a win over a
photon rocket (itself very poor for low delta-V) if one can
efficiently re-use the effect 1/F times.
- Tim
Suzanne Blom
"Brian M. Scott" <b.s...@csuohio.edu> wrote in message
news:l4vlm9vwxu49.x...@40tude.net...
least, that's how I understood it.
Ric Locke
So the ancestor is Proto-Germanic, whence English "blood" and German
"blut", yes?
Regards,
Ric
Ric Locke
Everyone lacks the necessary language, including the scientists who
"know" the subject. Language names and identifies the things of our
experience; subatomic particles and the like are not part of our
experience, not directly accessible to our senses, so we must refer to
them by metaphor, simile, and analogy. Even the word "particle" is a
metaphor.
Regards,
Ric
R.L.
> "R.L." <see...@no-spams.coms> wrote:
>
>>On Sat, 12 Dec 2009 08:03:32 -0500, Michelle Bottorff wrote:
>>
>>> Eric Ammadon <n...@spam.thankee> wrote:
>>>
>>>>>Space can get emptier than absolutely empty,
>>>>
>>>> That statement is so obviously stupid that I'm amazed.
>>>
>>> Welcome to quantum physics.
>
> Odd, I didn't see Michelle's response, but I see your response to her
> response.
Time and space get odd here. Welcome to Usenet.
>>> It's perfectly possible to work out the math for "emptier than
>>> absolutely empty" you know. That's what those little '-' signs are for.
>>
>>
>>As in 'less than nothing'? -1?
>>
>>What's hard about that?
>
> Show me an actual -1, not a "borrowed" one, not a conceptual thing you
> can use but not touch, and we'll talk.
Show me an 'absolutely empty' that we can touch.
R.L.
Ben Crowell
Great post, Tim, thanks.
One thing I don't understand is that the article only talks about using
it for attitude control, but it seems like flywheels accomplish that
trivially, with low technology and low use of energy -- so I don't
really see what the point would be. I'm not clear on why they talk
about attitude control rather than propulsion. Is it (a) because
it can't be used for propulsion, or (b) because it can be used for
propulsion, but the thrust is too ridiculously low to be useful?
The idea that you can store linear momentum in a box full of vacuum
violates my intuition far more strongly than the idea that you can
store angular momentum in the same way -- but I don't claim that my
physical intuition is well trained on the Casimir effect :-)
Eric Ammadon
If you've read the posts on this topic from those who have an actual
background in physics (and I expect you have read them), you might
have noticed that the language used in the referenced articles was
sloppy enough that people who have physics backgrounds were
misinterpreting their content. Those of us who have not specialized
in physics have little chance of understanding what was written
about... it's been my opinion for many years that every "scientist"
should have a tech-writer at his side at all times so that when they
publish it's at least understandable to others who might wish to
reproduce their results. It really should not be necessary to have to
attempt to reverse-engineer the whole business from a few clues that
have leaked out in spite of the discoverer's effective illiteracy.
Eric Ammadon
>On Sun, 13 Dec 2009 02:13:15 -0700, Eric Ammadon
><n...@spam.thankee> wrote in
><news:co99i5930dg4l17bn...@4ax.com> in
>rec.arts.sf.composition:
>
>> "Suzanne Blom" <sue...@execpc.com> wrote:
>
>>> A mundane analogy. Suppose a holdup man tries to mug me,
>>> and discovers that my pockets are empty, gives up, and
>>> goes away in disgust. I reach into my pocket and pull
>>> out my lucky wooden nickel and give it a thinkful pat.
>>> Was the holdup man wrong when he decided my pockets
>>> were empty? No, in his frame of reference, my pockets
>>> were empty. Now that I've taken out the lucky piece
>>> are my pockets empty? Well, again, it depends. They
>>> do, after all, have some lint and some of that perfume
>>> from the laundry detergent coats the threads and like
>>> that.
>
>> Most people believe that in order to remove something from
>> their pocket it must first have been placed there by
>> mundane means. Having never experienced anything
>> inexplicable using the set of explanations they were
>> given as a child, they have no reason to question them.
>
>None of this has any bearing on Suzanne's point.
None that you are capable of gleaning at any rate, no.
>>> Again, back in the 1600's when people were deciding where
>>> the constellation lines should be drawn, there was this
>>> star that they named 10 Ursa Major. 10 UMa has now
>>> drifted into the constellation of Lynx. In this case,
>>> people have quietly started calling it by other names,
>>> but in some cases it's really hard to change the name
>>> or in the given field the meanings of the word/name has
>>> changed with the understanding of what's happening.
>>> This does make wandering into any field difficult.
>>> From football to physics, word names do not mean to an
>>> insider what they would to a naive outsider.
>
>> The fact that 10 Uma appears to us to have drifted into
>> Lynx does not by itself mean that it has changed
>> position, any more than the fact that the sun rises and
>> sets means that it circles the earth. I assume that you
>> realize that, and you are using it as an example because
>> you think I am an idiot.
>
>You're doing a good job of demonstrating it: apparently
>you've altogether missed the (rather straightforward) point
>of the example. Of course you *could* simply be avoiding
>it; it wouldn't be the first time.
Are you seriously attempting to join your two pals in my killfile? If
so just give the word, based on past posts from you I would lose out
on absolutely nothing whatsoever.
>> There were indeed about $30 of unexpected expenses, and
>> no, it was not my first experience with the inexplicable,
>> and no, I did not mistake the denomination of the bill.
>
>So you say. So, perhaps, you even believe.
>
>[...]
>
>> I still find it surprising, and sad, that here in a
>> newsgroup supposedly devoted to the writing of novels
>> about fantasy, magic, and science-fiction, the belief
>> that only what is placed in a pocket by mundane means can
>> be removed from it. So it goes.
>
>No one actually expressed such a belief. Not that it really
>matters: the idea that the writing of f/sf should be
>associated with a loss of critical faculties is just
>bizarre.
The fact that you consider any viewpoint other than your own, as it
has been given you by the mundane, to be equivalent to a "loss of
critical faculties" is very revealing.
Ric Locke
Ben, I apologize for offending you earlier. The post was intended to be
at least somewhat humorous; clearly I didn't frame it properly. I'm
aware that my understanding is deficient, and that I hold a lot of
preconceptions that are incorrect. I hope my prejudices aren't quite as
off-base as some, but am aware that they may be.
The article itself, we must remember, is a second-hand account rather
than the actual paper/proposal, and we have to account for the fact that
the person reporting didn't understand it correctly. It seems to me that
the researcher is more tentative about the results than the reporter is,
and of course enormously more so than those who skim the article and
infer reactionless-drive spaceships available from Toyota next week.
If momentum can be exchanged with the virtual particles in a "box full
of vacuum", that is (as you note) a startling result that requires close
examination in the light of, for instance, energy conservation laws,
regardless of the actual magnitude of the effect. It wouldn't be the
first time quantum effects have apparently violated Da Rules as then
understood -- but it wouldn't be the first time somebody made a mistake
in the math and people got all optimistic about the possibilities,
either.
Regards,
Ric
Gerry Quinn
spams.coms says...
Or an actual +1 for that matter.
In any case, things like electric charge seem to come in opposite
varieties, so that a charge of -1 has equivalent physical reality to a
charge of +1.
- Gerry Quinn
Brian M. Scott
wrote in 18uobogdncojn$.1dvz0bmopkdby$.d...@40tude.net:
> On Sun, 13 Dec 2009 14:31:22 -0500, Brian M. Scott wrote:
>
>> On Sat, 12 Dec 2009 14:56:40 -0700, Eric Ammadon <n...@spam.thankee>
>> wrote in
>> <news:5d18i5tvf1kr42pcp...@4ax.com> in
>> rec.arts.sf.composition:
>>
>> [...]
>>
>>> The very need to draw deficient analogies is evidence that a thing is
>>> not fully understood; was it truly understood, analogies would be
>>> unnecessary.
>>
>> There is some truth in this IF you limit yourself to communication
>> between people who already have the understanding and the appropriate
>> language in which to couch it, though even then analogies can be
>> useful, if only as shorthand. If one party lacks the necessary
>> language, however, analogy is likely to be the only way in which the
>> knowledgeable party can convey any sense of the ideas involved. In
>> this case it's obvious that you, like most of us, do lack the necessary
>> language and are therefore in no position to judge the understanding of
>> others.
> Everyone lacks the language, including the scientists who
> "know" the subject.
I don't agree: I consider the appropriate mathematics to be the
relevant language. You can argue that it's still in some sense
metaphorical, and you might even be right, but it's far less
bound by human experience than is ordinary human language, and
it does allow the clear expression of ideas that cannot otherwise
be conveyed.
[...]
Brian
Ben Crowell
> Ben, I apologize for offending you earlier. The post was intended to be
> at least somewhat humorous; clearly I didn't frame it properly. I'm
> aware that my understanding is deficient, and that I hold a lot of
> preconceptions that are incorrect. I hope my prejudices aren't quite as
> off-base as some, but am aware that they may be.
Hi, Ric -- very gracious of you. I probably shouldn't have been so
stiff-necked in the first place :-)
Ric Locke
In the sense Eric was trying to put across, all language is
"metaphorical". He doesn't like that; I see it as inevitable. The name
is not the thing, only a pointer to it.
Regards,
Ric
Ric Locke
Hey, it's USENET. Misunderstandings, some deliberate, are a feature.
Regards,
Ric
Erik Max Francis
No they aren't! :-)
--
Erik Max Francis && m...@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 18 N 121 57 W && AIM/Y!M/Skype erikmaxfrancis
Can I walk with you / 'Till the day that my heart stops beating
-- India Arie
Ric Locke
> Ric Locke wrote:
>> On Mon, 14 Dec 2009 08:35:13 -0800, Ben Crowell wrote:
>>
>>> Ric Locke wrote:
>>>> Ben, I apologize for offending you earlier. The post was intended to be
>>>> at least somewhat humorous; clearly I didn't frame it properly. I'm
>>>> aware that my understanding is deficient, and that I hold a lot of
>>>> preconceptions that are incorrect. I hope my prejudices aren't quite as
>>>> off-base as some, but am aware that they may be.
>>> Hi, Ric -- very gracious of you. I probably shouldn't have been so
>>> stiff-necked in the first place :-)
>>
>> Hey, it's USENET. Misunderstandings, some deliberate, are a feature.
>
> No they aren't! :-)
Yes they are! And you're a [insert appropriate negative
characterization, in ALL CAPS]!
Regards,
Ric
Richard D. Latham
Sounds like one of those times when having a handy tame black hole
around to drop the momentum into could lead to some curious effects.
--
#include <disclaimer.std> /* I don't speak for IBM ... */
/* Heck, I don't even speak for myself */
/* Don't believe me ? Ask my wife :-) */
Richard D. Latham lat...@us.ibm.com or lat...@verizon.net
Brian M. Scott
<warric...@gmail.com> wrote in
<news:747ho8e13215.53gndidt143a$.d...@40tude.net> in
rec.arts.sf.composition:
> On Sun, 13 Dec 2009 13:10:37 -0500, Brian M. Scott wrote:
>> On Sat, 12 Dec 2009 19:19:52 -0600, Ric Locke
>> <warric...@gmail.com> wrote in
>> <news:veljksbc3fqj.1kf8srcktharm$.d...@40tude.net> in
>> rec.arts.sf.composition:
[...]
>>> just as "blood" comes from German.
>>
>> No, <blood> is from Old English <bl�d>, from Proto-Germanic
>> *blo:dam 'blood', whence also Gothic <bl��>, Old Norse
>> <bl��>, Old High German <bluot>, and German <Blut>.
> So the ancestor is Proto-Germanic, whence English "blood"
> and German "blut", yes?
Exactly.
Brian
Brian M. Scott
<n...@spam.thankee> wrote in
<news:ktubi5dttukh7mmuh...@4ax.com> in
rec.arts.sf.composition:
> "Brian M. Scott" <b.s...@csuohio.edu> wrote:
[...]
>>None of this has any bearing on Suzanne's point.
> None that you are capable of gleaning at any rate, no.
Or anyone else capable of reading English and thinking at
all clearly. You do make a habit of resorting to evasion
and non sequitur when pressed; I've yet to decide to what
extent this is a conscious defense mechanism and to what
extent it's merely the result of fuzzy thinking.
[...]
> Are you seriously attempting to join your two pals in my
> killfile?
Not particularly, though I can't say that I'd be greatly
distressed if I did: if I used a killfile for anything but
the recent invasion of out and out spam, you'd be one of the
likeliest candidates. Feel free; it's not likely to keep me
from the occasional comment when you say something
exceptionally silly or nasty, but it might protect your ego.
[...]
> ... any viewpoint other than your own, as it has been
> given you by the mundane, [...]
Ah, more ego protection. Distressing as you may find it, my
views -- even the relatively conventional ones -- are my
own, not adopted blindly from the masses.
Eric Ammadon
>On Mon, 14 Dec 2009 01:52:13 -0700, Eric Ammadon
><n...@spam.thankee> wrote in
><news:ktubi5dttukh7mmuh...@4ax.com> in
>rec.arts.sf.composition:
>
>> "Brian M. Scott" <b.s...@csuohio.edu> wrote:
>
>[...]
>
>>>None of this has any bearing on Suzanne's point.
>
>> None that you are capable of gleaning at any rate, no.
>
>Or anyone else capable of reading English and thinking at
>all clearly. You do make a habit of resorting to evasion
>and non sequitur when pressed; I've yet to decide to what
>extent this is a conscious defense mechanism and to what
>extent it's merely the result of fuzzy thinking.
All thinking unlike your own is then, "fuzzy"?
> Distressing as you may find it, my
>views -- even the relatively conventional ones -- are my
>own, not adopted blindly from the masses.
So you were never blind for a moment, even as a child; why should I be
distressed by such good fortune? Surprised perhaps, but not
distressed, that a being evolved with never a doubt about Santa Claus,
always knew that some of the things mommy and daddy said were not as
true as they believed them to be.
If you are as you wish to believe yourself, perhaps you might someday
find yourself able to conceive a place from which what now appears to
you as "evasion and non sequitur" is just the opposite.
Until then the mathematician in you might ponder the circumstances
under which fuzzy logic is clear, ways that a subroutine within a box
can handle its inputs, because stripped of the often unfounded belief
that we understand the universe we are none of us better off than
blind subroutines responding to inputs.
I expect instead that you will continue by rote, and hope to be
mistaken.
Daniel R. Reitman
wrote:
>Brian M. Scott wrote:
>> On Wed, 09 Dec 2009 07:43:53 -0900, Bill Swears
>> <wsw...@gci.net> wrote in
>> <news:vqidnabI255UToLW...@posted.mtasolutions>
>> in rec.arts.sf.science,rec.arts.sf.composition:
>>
>>> Jonathan L Cunningham wrote:
>>
>>>> But the crucial word there is "possible". Space doesn't vibrate in
>>>> impossible ways - that would be impossible. (Impossible things are
>>>> impossible, fortunately, otherwise we'd all get confused.)*
>>
>>> * (Unless you are a Marine).
>>
>> Aren't you thinking of the WWII motto of the U.S. Army Corps
>> of Engineers?
>>
>> Brian
>The impossible takes a little bit longer?
I usually can only fit in five before breakfast.
Dan, ad nauseam