A couple odd questions
Kitarak
(well. almost every week, I've been slipping a bit recently). The one I'm
currently thinking of right now is a science fiction one, and I'm trying to get
some of the basic details right.
The real problems I'm having all stem around the technology that forms the
basis for most of the setting. The Force-field. But it's not like force-fields
in most fiction. The basic idea of this force-field is as follows:
Force-fields are effectively a solid object, but they aren't made up of
particles. They are continuous, and nearly massless. A force-field is
infinitely thin, but the edges can be joined together to form hollow, three
dimensional objects. A force-field is impassable to anything travelling at less
than the speed of light. It can be altered to allow different types of luxons
through, including different wavelengths of light. Force-fields are not
infinitely rigid, but they are as rigid as SR allows (i.e. Speed of sound in a
forcefield is equal to the speed of light). Force-fields do have mass, but it
is exceptionally low. While they are influenced by gravity, they do not cause
gravity on their own. Also, energy can be transferred to or from a force-field,
and force-fields can be caused to absorb energy, acting as a solar panel. A
force-field requires a special force-field generator to maintain, but does not
need one to maintain it - A smaller device is required to keep it stable for
long periods of time, but they are cheap and require little power. A
force-field will last several days without stabilisation. (Note: To create a
force-field you need to supply it's mass energy and more, so you can't use it
to violate conservation of energy).
Anyway, sorry to bore you with those details, but they're reasonably neccesary
to understand the questions coming up. (Or at least to get them in context).
Firstly, what uses can you think of for these force-fields? I've come up with:
Mega-structures: Dyson Spheres, Ringworlds, Orbital towers, etc. A force-field
should be strong enough.
Solar Sails: A perfectly reflective force-field is the ideal solar sail - It is
far lighter than any possible material.
Solar Panels: A solar panel can be made almost any size if you use a
force-field, and work with almost perfect efficiency.
Containment for anti-matter
Radiators for space-ships
Power Conduits between space stations
Orbital 'bridges' - Railways between different places in space allowing easy
travel (with a forcefield light-sail to help maintain position possibly)
Communications - There's very little danger of noise if you send the signal
down a series of force-field monofilaments, and it travels at the speed of
light.
The obvious defense device
Some sort of force-field ramscoop? (I actually have a better mechanism for this
in the setting, it was just a thought).
Anyway, here are the main questions:
What would the power output from a perfectly efficient solar panel which was a
disk half a light-year across, when it is in interstellar space (About 2-4
light-years from the nearest star).
What is the maximum size a light-sail could be to pass through the system
safely (Not material limited, limited to avoid hitting inconveniently placed
planets, asteroids, etc.)
What is the total power output of the sun? There won't be a proper dyson
sphere, but I'm looking for a maximum power output for the Web (You'll have to
see the finished version in rec.games.frp.gurps for more details :-).
Is it possible to block the electromagnetic force? In particular if you had a
force-field set to block all photons and other luxons, would it block
intermolecular forces? (Force-field weaponry - You can't really cut properly
with a 2D object, but if it can block the intermolecular forces of an
object...)
Thanks in advance.
--------------------------------------
Kitarak
This is a Chain Letter. Forget your gods. Be Subjugated. Learn to Fear. Do not
break the chain - the last people who did woke up one morning to find fifty
thousand armed men on their lawn.
Erik Max Francis
> Every week in rec.games.frp.gurps ...
I've always been puzzled why "FRP" was chosen for the acronym
(especially when RPG is available) for that particular hierarchy, since
not all of its subgroups are about _fantasy_ roleplaying games, but
that's my own thing, I guess ...
> The real problems I'm having all stem around the technology that forms
> the
> basis for most of the setting. The Force-field.
Note that when physicists say "force field," they mean something much
more mundane, but I imagine you knew that ...
> Force-fields are effectively a solid object, but they aren't made up
> of
> particles. They are continuous, and nearly massless.
For which values of "massless"? :-)
> While they are influenced by gravity, they do not cause
> gravity on their own.
That's a hard one to swallow. There's got to be an enormous amount of
energy involved in creating these fields (not necessarily maintaining
them, though), and energy generates gravitational fields under general
relativity.
I know you're not trying to rationalize _how_ (physically) the fields
are generated (and you almost certainly shouldn't), but that kind of
requirement probably doesn't make sense. Since you're getting into the
realm of Known Space near-magical technology, though, it's a little hard
to bring known science into it.
> Also, energy can be transferred to or from a force-field,
> and force-fields can be caused to absorb energy, acting as a solar
> panel.
Gee, how convenient.
> (Note: To create a
> force-field you need to supply it's mass energy and more, so you can't
> use it
> to violate conservation of energy).
Problem is, it would probably be quite large indeed.
> Firstly, what uses can you think of for these force-fields? I've come
> up with:
Well, it sounds like you could pretty much use them for whatever you
like; they're sufficiently magical to accomodate whatever you like.
> Anyway, here are the main questions:
>
> What would the power output from a perfectly efficient solar panel
> which was a
> disk half a light-year across, when it is in interstellar space (About
> 2-4
> light-years from the nearest star).
The insolation I form a body of power P at a distance R is
I = P/(4 pi R^2).
For a sail of area A tilted at an angle theta from the normal (so if
perpendicular, theta = 0), the intercepted power J is
J = I A cos theta.
> What is the maximum size a light-sail could be to pass through the
> system
> safely (Not material limited, limited to avoid hitting inconveniently
> placed
> planets, asteroids, etc.)
On the order of the size of the orbits between planets. That is, not a
consideration.
> What is the total power output of the sun?
3.846 x 10^26 W
--
Erik Max Francis | icq 16063900 | whois mf303 | email m...@alcyone.com
Alcyone Systems | irc maxxon (efnet) | web http://www.alcyone.com/max/
San Jose, CA | languages en, eo | icbm 37 20 07 N 121 53 38 W
USA | Wed 1999 Oct 20 (34%/950) | &tSftDotIotE
__
/ \ Wars may be fought with weapons, but they are won by men.
\__/ Gen. George S. Patton
Mr. M.J. Lush
Erik Max Francis <m...@alcyone.com> wrote:
>Kitarak wrote:
>
>> Every week in rec.games.frp.gurps ...
>
>I've always been puzzled why "FRP" was chosen for the acronym
>(especially when RPG is available) for that particular hierarchy, since
>not all of its subgroups are about _fantasy_ roleplaying games, but
>that's my own thing, I guess ...
There is a rec.games.rpg unfortunately (probably due to fumbled
there create newsgroup skill roll) its not widely propagated and
doesn't attract many posts.
--
Michael
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NPC rights activist | Nameless Abominations are people too.
Andrew Plotkin
> gravity on their own.
General Relativity nearly assures that they *will* cause gravity, exactly
as a solid object of equal mass.
(I say "nearly" because this is fantasy physics, of course, and you can
make up any rules you want. But keeping GR is nice.)
> Firstly, what uses can you think of for these force-fields?
Arbitrary tools. House-in-a-box. Skyscraper-in-a-box. Office partitions
that are trivial to rearrange. Boat hulls. Near-zero-weight airplane
wings. Build a box in orbit, attach weights, drop it into the atmosphere:
it's a near-zero-weight vacuum blimp. Walls for undersea tunnels. Walls
for undersea cities. Highway surfacing that will never wear out.
Unbreakable windows, dinner plates, fences, and microscope slides.
How precisely can you control photon reflection at different places in the
field? Could make a laptop screen or a mile-high programmable billboard.
Can you change the shape of the thing at run-time? Pumps, elevators,
vehicle drives (crawler tracks).
Now get clever. A radio-impermeable force field can be used for microwave
waveguides. Make arbitrarily-shaped antennas and comm channels. Force rods
in vacuum can make dandy rod-logic computers. Add a solar-absorber force
field for a power source, and you have arbitrary electronic, electrical,
and computational equipment. Design a computer, punch the design into your
force-field generator, and you have the working model sitting in front of
you. (Naturally, you do the work *on* a computer which was made this
way... The only part made of mere gross *matter* is the force-field
generator.)
--Z
"And Aholibamah bare Jeush, and Jaalam, and Korah: these were the
borogoves..."
Kitarak
>Kitarak wrote:
>
>> Every week in rec.games.frp.gurps ...
>
>I've always been puzzled why "FRP" was chosen for the acronym
>(especially when RPG is available) for that particular hierarchy, since
>not all of its subgroups are about _fantasy_ roleplaying games, but
>that's my own thing, I guess ...
Actually, FRP doesn't mean the fantasy genre. It means Fantasy as in 'not
real'.
>> The real problems I'm having all stem around the technology that forms
>> the
>> basis for most of the setting. The Force-field.
>
>Note that when physicists say "force field," they mean something much
>more mundane, but I imagine you knew that ...
Yes. I did. But I liked the name...
>> Force-fields are effectively a solid object, but they aren't made up
>> of
>> particles. They are continuous, and nearly massless.
>
>For which values of "massless"? :-)
Inertial, gravitational, etc. They have a low energy (if they're not too big).
>That's a hard one to swallow. There's got to be an enormous amount of
>energy involved in creating these fields (not necessarily maintaining
>them, though), and energy generates gravitational fields under general
>relativity.
See my other reply to why I needed that. I'd appreciate a solution. I'm afraid
I don't see how to get around it. And why do they need high amounts of energy
to create? This being fake-science I can say they operate on some, as yet
undiscovered, principle. :-)
>I know you're not trying to rationalize _how_ (physically) the fields
>are generated (and you almost certainly shouldn't)
I don't intend too...
>, but that kind of
>requirement probably doesn't make sense. Since you're getting into the
>realm of Known Space near-magical technology, though, it's a little hard
>to bring known science into it.
Well. The problem isn't so much science (There's a fairly... loose... attitude
to the physical laws in this setting), it's more realism. As in, I don't mind
if it's physically impossible (although it's nice for it to be vaguely
possible), but I'd like to get the numbers for the possible parts right.
>> Also, energy can be transferred to or from a force-field,
>> and force-fields can be caused to absorb energy, acting as a solar
>> panel.
>
>Gee, how convenient.
Well it is their main use in the setting...
>> What would the power output from a perfectly efficient solar panel
>> which was a
>> disk half a light-year across, when it is in interstellar space (About
>> 2-4
>> light-years from the nearest star).
>
>The insolation I form a body of power P at a distance R is
>
> I = P/(4 pi R^2).
>
>For a sail of area A tilted at an angle theta from the normal (so if
>perpendicular, theta = 0), the intercepted power J is
>
> J = I A cos theta.
Thanks.
>> What is the maximum size a light-sail could be to pass through the
>> system
>> safely (Not material limited, limited to avoid hitting inconveniently
>> placed
>> planets, asteroids, etc.)
>
>On the order of the size of the orbits between planets. That is, not a
>consideration.
With these force-fields it is. :-) But I've just realised, the force-field has
to pass through the gaps in the web (large quasi-dyson sphere/swarm type
object), which puts a much lower limit on it...
>> What is the total power output of the sun?
>
>3.846 x 10^26 W
>
Ah. Plenty then. :-)
Thanks...
Kitarak
<erky...@netcom.com> writes:
>Kitarak <kit...@aol.com> wrote:
>> Force-fields do have mass, but it
>> is exceptionally low. While they are influenced by gravity, they do not
>cause
>> gravity on their own.
>
>General Relativity nearly assures that they *will* cause gravity, exactly
>as a solid object of equal mass.
Hmm... Well the real problem with them having gravity is that they will produce
nearly infinite gravity near to them, as they are infinitely thin. Or does GR
solve that problem?
>(I say "nearly" because this is fantasy physics, of course, and you can
>make up any rules you want. But keeping GR is nice.)
I agree. It's on my list of 'Try not to violate but don't get too bothered if
you do'. On the list of 'Do not violate unless you want to move into science
fantasy' are the various conservation laws and to some degree SR
(Thermodynamics is a borderline... I know it's important, but there's too many
fun things that violating it allows).
>> Firstly, what uses can you think of for these force-fields?
>
>Arbitrary tools. House-in-a-box. Skyscraper-in-a-box. Office partitions
>that are trivial to rearrange. Boat hulls. Near-zero-weight airplane
>wings. Build a box in orbit, attach weights, drop it into the atmosphere:
>it's a near-zero-weight vacuum blimp. Walls for undersea tunnels. Walls
>for undersea cities. Highway surfacing that will never wear out.
>Unbreakable windows, dinner plates, fences, and microscope slides.
>
>How precisely can you control photon reflection at different places in the
>field?
Not very precisely. You can create areas of specific reflection, but the edges
will blur. You can control the values in the defined areas very specifically
though.
>Could make a laptop screen or a mile-high programmable billboard.
>Can you change the shape of the thing at run-time? Pumps, elevators,
>vehicle drives (crawler tracks).
Yes, but it's harder than building an unmoving forcefield.
>Now get clever. A radio-impermeable force field can be used for microwave
>waveguides. Make arbitrarily-shaped antennas and comm channels. Force rods
>in vacuum can make dandy rod-logic computers. Add a solar-absorber force
>field for a power source, and you have arbitrary electronic, electrical,
>and computational equipment. Design a computer, punch the design into your
>force-field generator, and you have the working model sitting in front of
>you. (Naturally, you do the work *on* a computer which was made this
>way... The only part made of mere gross *matter* is the force-field
>generator.)
Heh. That could be fun. Unfortunately I wasn't thinking of quite that high
precision in forcefields. It changes the setting a lot from what I wanted...
Dwight Thieme
: In article <7ukka5$hfk$2...@nntp3.atl.mindspring.net>, Andrew Plotkin
: <erky...@netcom.com> writes:
: >Kitarak <kit...@aol.com> wrote:
: >> Force-fields do have mass, but it
: >> is exceptionally low. While they are influenced by gravity, they do not
: >cause
: >> gravity on their own.
: >
: >General Relativity nearly assures that they *will* cause gravity, exactly
: >as a solid object of equal mass.
: Hmm... Well the real problem with them having gravity is that they will produce
: nearly infinite gravity near to them, as they are infinitely thin. Or does GR
: solve that problem?
No, it won't. Look up any undergraduate physics text to see the
derivation of a finite force produced by an infinite plane whose
sole parameter is the mass per unit *area*.
Ike
Brooks Moses
[Regarding some specific sort of "force-field" in his role-playing game]
> Force-fields do have mass, but it
> is exceptionally low. While they are influenced by gravity, they do not cause
> gravity on their own.
Hmm ... do you really need this? If they are really essentially
massless, then you might as well have them cause gravity in the amounts
expected from their mass -- which would be very small and negligible for
practical purposes, of course.
Otherwise, you're left with a planet pulling on the force-field, but the
force-field not pulling back on the planet, which would seem to violate
conservation of momentum.... And this, IMHO, is a bad thing.
- Brooks
Kitarak
(Dwight Thieme) writes:
>No, it won't. Look up any undergraduate physics text to see the
>derivation of a finite force produced by an infinite plane whose
>sole parameter is the mass per unit *area*.
Except of course that the force-fields are neither infinite nor a plane - They
are of decidedly finite size, and they can be folded into all sorts of
shapes...
Dwight Thieme
: In article <7uktas$gj2$1...@dipsy.missouri.edu>, c36...@cclabs.missouri.edu
: (Dwight Thieme) writes:
: >No, it won't. Look up any undergraduate physics text to see the
: >derivation of a finite force produced by an infinite plane whose
: >sole parameter is the mass per unit *area*.
: Except of course that the force-fields are neither infinite nor a plane - They
: are of decidedly finite size, and they can be folded into all sorts of
: shapes...
. . . And therefore will have even less attraction than the infinite
plane case; iow, gravitional attraction will not be 'nearly infinite'.
Ike
Kitarak
writes:
>Hmm ... do you really need this? If they are really essentially
>massless, then you might as well have them cause gravity in the amounts
>expected from their mass -- which would be very small and negligible for
>practical purposes, of course.
No it wouldn't. The forcefields are infinitely thin, so when you're really
close to it...
>Otherwise, you're left with a planet pulling on the force-field, but the
>force-field not pulling back on the planet, which would seem to violate
>conservation of momentum.... And this, IMHO, is a bad thing.
I agree. But I can't seem to find a way around it. :-(
Brooks Moses
> In article <380E22FC...@stanford.edu>, Brooks Moses <bmo...@stanford.edu>
> writes:
> >Hmm ... do you really need this? If they are really essentially
> >massless, then you might as well have them cause gravity in the amounts
> >expected from their mass -- which would be very small and negligible for
> >practical purposes, of course.
>
> No it wouldn't. The forcefields are infinitely thin, so when you're really
> close to it...
They are only "infinitely thin" in one out of three dimensions -- which
is not at all the same thing as being a point mass that's "infinitely
small" in all three directions. In the case of a thin sheet, it's not a
problem, because you can only get really close to a single point on the
forcefield, and that point by itself has zero mass. Consider it like
this:
|
/|
You |
\|
|
The "|" is the forcefield. Because gravitational force drops off as
1/r^2 for a given point source, and only the normal components don't get
canceled, the gravity from the parts of the forcefield that are outside
the cone denoted by "/" and "\" is negligible compared to that from
what's inside it. (Ok, so I'm handwaving a bit. But this is clearly
intuitively true for some sufficiently large cone angle! And, if you're
uncertain, I can go into details.) As you get closer and closer, the
gravitational attraction from each point source goes up essentially as
1/r^2. However, the amount of forcefield within that cone decreases as
1/r^2, which cancels this out quite pleasantly, and so the total
gravitational force is _constant_ when you are close to the field. It
does _not_ go to infinity!
This is, of course, what others were saying with the infinite-thin-plane
analogy -- note that when you get really close, the curvature and
boundaries of your force-field are on a much larger scale than the
distance between you and the force-field (if they aren't, simply get
closer and they will be!) and so the difference between the
infinite-thin-plane case and your case becomes negligibly small, and the
same results of non-infinite gravitational force apply when you are very
close.
> >Otherwise, you're left with a planet pulling on the force-field, but the
> >force-field not pulling back on the planet, which would seem to violate
> >conservation of momentum.... And this, IMHO, is a bad thing.
>
> I agree. But I can't seem to find a way around it. :-(
It's only a problem if you worry, incorrectly, about the gravity going
to infinity when you get really close.
Moreover, if that _was_ a problem, mathematical symmetry would apply and
you'd still have the concurrent problem of something very close to the
forcefield pulling on the forcefield with a gravitational force that
went to infinity as the forcefield got closer. Which would be equally
bad, I think.
- Brooks
Alan D Kohler
wrote:
>Kitarak wrote:
>
>> Every week in rec.games.frp.gurps ...
>
>I've always been puzzled why "FRP" was chosen for the acronym
>(especially when RPG is available) for that particular hierarchy, since
>not all of its subgroups are about _fantasy_ roleplaying games, but
>that's my own thing, I guess ...
The hobby is sometimes called "fantasy role playing" - albeit the fact
that all genres played with it are not fantasy, whenever you are
playing a role-playing game, you are engaging in a sort of
rules-assisted fantasy.
Also, CRPGS (which are really not RPGs IMO) steal the term RPG
frequently. I bet you'd see a lot more people asking for diablo cheat
codes or whatever if it was called "rpg."
Of course, this is a total aside, but you asked (after a fashion.)
Alan D. Kohler(hawk...@NOSPAM.olg.com)
"I once shot a man in Nepal just to watch him reincarnate." -Wierd Al
Hawkwind's RPG Pages are back at last!
http://members.tripod.com/~hawk_wind/homepage.html
MA Lloyd
>In article <380D8C25...@alcyone.com>,
>Erik Max Francis <m...@alcyone.com> wrote:
>>Kitarak wrote:
>>
>>I've always been puzzled why "FRP" was chosen for the acronym
>>(especially when RPG is available) for that particular hierarchy, since
>>not all of its subgroups are about _fantasy_ roleplaying games, but
>>that's my own thing, I guess ...
> There is a rec.games.rpg unfortunately (probably due to fumbled
>there create newsgroup skill roll) its not widely propagated and
>doesn't attract many posts.
As I understand rec.games.frp was created when D&D was the only one available.
At some point before the group divided some fool created rec.games.rpg
by issuing the control messages without going through the agreed process,
which resulted in *.rpg going on blacklists all over the net, from which it
could probably never be removed completely - hence to avoid propagation
problems it has been avoided ever since.
--
-- MA Lloyd (mall...@io.com)
Erik Max Francis
> Hmm... Well the real problem with them having gravity is that they
> will produce
> nearly infinite gravity near to them, as they are infinitely thin. Or
> does GR
> solve that problem?
All you need is Newtonian gravitation and calculus and a knowledge of
how approximations are used in physics.
If you have an infinitely large plane, with a finite areic mass, then
the gravitational field _everywhere_ is constant (directed to the
plane), and is proportional to the plane's areic mass.
Now take a finite plane of size r, and a test mass at distance R from
the plane. If you want to measure the gravitational field from the
plane at the test mass, then it depends on how r and R compare. If R >>
r (R much greater than r), then you can approximate the plane as a point
mass, and simply compute the Newtonian gravitational field from the
total mass of the finite plane (areic mass times area).
If r << R (and the point is not near the edges of the plane), then that
means your test point is _very_ close to the plane -- so close that you
can approximate the plane as being infinite in size, and in that
approximate the field is constant. So as you move the test point from
far away to extremely close, the field varies from a 1/r^2 field to
something roughly constant.
If you get arbitrarily close to a _point mass_, then the gravitational
field strength will diverge. But this isn't a point mass, and so you
can only be arbitrarily close to an arbitrarily small part of it, so you
don't have a problem.
--
Erik Max Francis | icq 16063900 | whois mf303 | email m...@alcyone.com
Alcyone Systems | irc maxxon (efnet) | web http://www.alcyone.com/max/
San Jose, CA | languages en, eo | icbm 37 20 07 N 121 53 38 W
USA | Wed 1999 Oct 20 (36%/950) | &tSftDotIotE
__
/ \ Then conquer we must, for our cause is just ...
\__/ Francis Scott Key
Tom Breton
> Kitarak wrote:
>
> > Every week in rec.games.frp.gurps ...
>
> I've always been puzzled why "FRP" was chosen for the acronym
> (especially when RPG is available) for that particular hierarchy, since
> not all of its subgroups are about _fantasy_ roleplaying games, but
> that's my own thing, I guess ...
"Fantasy" as opposed to reality, not "fantasy" as opposed to science
fiction, horror, historical etc.
--
Tom Breton, http://world.std.com/~tob
Not using "gh" since 1997. http://world.std.com/~tob/ugh-free.html
Erik Max Francis
> See my other reply to why I needed that. I'd appreciate a solution.
> I'm afraid
> I don't see how to get around it.
There probably isn't one, unless you want to get into enough handwaving
in other areas that you might as well have not have tried.
> And why do they need high amounts of
> energy
> to create? This being fake-science I can say they operate on some, as
> yet
> undiscovered, principle. :-)
But to be able to be "solid," they're going to have to have very strong,
dense electromagnetic fields -- similar to the electromagnetic fields
generated in matter. That's going to involve a high energy density, and
since in general relativity, energy generates gravitation too (though
not quantitatively the same as matter), it should have a noticeable
gravitational field.
> Well. The problem isn't so much science (There's a fairly... loose...
> attitude
> to the physical laws in this setting), it's more realism.
Well, they're rather related, wouldn't you say? :-)
--
Erik Max Francis | icq 16063900 | whois mf303 | email m...@alcyone.com
Alcyone Systems | irc maxxon (efnet) | web http://www.alcyone.com/max/
San Jose, CA | languages en, eo | icbm 37 20 07 N 121 53 38 W
USA | Wed 1999 Oct 20 (37%/950) | &tSftDotIotE
__
/ \ Some mistakes we must carry with us.
\__/ Speaker-to-Animals
Riboflavin
>ml...@hgmp.mrc.ac.uk (Mr. M.J. Lush) writes:
>> There is a rec.games.rpg unfortunately (probably due to fumbled
>>there create newsgroup skill roll) its not widely propagated and
>>doesn't attract many posts.
>
>As I understand rec.games.frp was created when D&D was the only one
available.
That would be pretty impressive, considering how long other RPGs have been
around. My champions book has its oldest copyright in 1981, and I'm pretty
sure Champions wasn't the first successful non-D&D RPG. The modern naming
convention for newsgroups didn't come into effect until sometime in the mid
to late 80's, so there's no way the group rec.games.frp could have been
created when D&D was the only game available (more accurately, no group
whose name started with "rec." would have been created then).
--
Kevin Allegood ribotr...@mindspring.pants.com
Remove the pants from my email address to reply
"I am convinced people who worry about spelling and punctuation
on the net fold their underwear before they have sex. It's just got to be."
- Bunboy
Andrew Plotkin
> In article <380E22FC...@stanford.edu>, Brooks Moses <bmo...@stanford.edu>
> writes:
>
>>Hmm ... do you really need this? If they are really essentially
>>massless, then you might as well have them cause gravity in the amounts
>>expected from their mass -- which would be very small and negligible for
>>practical purposes, of course.
>
> No it wouldn't. The forcefields are infinitely thin, so when you're really
> close to it...
Electrons are pretty-much-infinitely small, and they they a nonzero mass.
It works out somehow.
You could say force fields work like *that*.
Kitarak
<ri...@mindspring.com> writes:
>That would be pretty impressive, considering how long other RPGs have been
>around. My champions book has its oldest copyright in 1981, and I'm pretty
>sure Champions wasn't the first successful non-D&D RPG. The modern naming
>convention for newsgroups didn't come into effect until sometime in the mid
>to late 80's, so there's no way the group rec.games.frp could have been
>created when D&D was the only game available (more accurately, no group
>whose name started with "rec." would have been created then).
Perhaps he meant rec.games.frp.dnd was the only available .frp group...
James Nicoll
Kitarak <kit...@aol.com> wrote:
>In article <7um9dh$sle$2...@nntp6.atl.mindspring.net>, "Riboflavin"
><ri...@mindspring.com> writes:
>
>>That would be pretty impressive, considering how long other RPGs have been
>>around. My champions book has its oldest copyright in 1981, and I'm pretty
>>sure Champions wasn't the first successful non-D&D RPG. The modern naming
>>convention for newsgroups didn't come into effect until sometime in the mid
>>to late 80's, so there's no way the group rec.games.frp could have been
>>created when D&D was the only game available (more accurately, no group
>>whose name started with "rec." would have been created then).
>
>Perhaps he meant rec.games.frp.dnd was the only available .frp group...
>
not .dnd. I mean, even by 1980 there were dozens of competing RPGs.
My first games were Traveller and Runequest.
--
"You know, it's getting more and more like _Blade Runner_ down
here."
A customer commenting on downtown Kitchener
Riboflavin
>Perhaps he meant rec.games.frp.dnd was the only available .frp group...
>
Joseph Hertzlinger
>Force-fields are effectively a solid object, but they aren't made up of
>particles. They are continuous, and nearly massless. A force-field is
>infinitely thin, but the edges can be joined together to form hollow, three
>dimensional objects. A force-field is impassable to anything travelling at less
>than the speed of light. It can be altered to allow different types of luxons
>through, including different wavelengths of light. Force-fields are not
>infinitely rigid, but they are as rigid as SR allows (i.e. Speed of sound in a
>forcefield is equal to the speed of light). Force-fields do have mass, but it
>is exceptionally low.
The force-fields as described can't be infinitesimally thin. Bending
resistance is proportional to the square of the thickness. An
infinitesimally thin beam or plate with a finite surface density and
speed of sound will be infinitely floppy.
The force-fields can be very thin, of course.
>This is a Chain Letter. Forget your gods. Be Subjugated. Learn to Fear. Do not
>break the chain - the last people who did woke up one morning to find fifty
>thousand armed men on their lawn.
What does that mean?
Erik Max Francis
Do you know what a chain letter is?
--
Erik Max Francis | icq 16063900 | whois mf303 | email m...@alcyone.com
Alcyone Systems | irc maxxon (efnet) | web http://www.alcyone.com/max/
San Jose, CA | languages en, eo | icbm 37 20 07 N 121 53 38 W
USA | Fri 1999 Oct 22 (41%/950) | &tSftDotIotE
__
/ \ Take a look at your face
\__/ Level 42
Kitarak
(Joseph Hertzlinger) writes:
>The force-fields as described can't be infinitesimally thin. Bending
>resistance is proportional to the square of the thickness. An
>infinitesimally thin beam or plate with a finite surface density and
>speed of sound will be infinitely floppy.
Err. Ok then. Very thin. (On the order of atomic radius thicknesses).
>The force-fields can be very thin, of course.
>
>>This is a Chain Letter. Forget your gods. Be Subjugated. Learn to Fear. Do
>not
>>break the chain - the last people who did woke up one morning to find fifty
>>thousand armed men on their lawn.
>
>What does that mean?
Quote from Discworld - Small gods. Great book. :-)
--------------------------------------
Kitarak
Joseph Hertzlinger
>In article <7uoum1$lmn$1...@nntp5.atl.mindspring.net>, jher...@ix.netcom.com
>(Joseph Hertzlinger) writes:
>
>>The force-fields as described can't be infinitesimally thin. Bending
>>resistance is proportional to the square of the thickness. An
>>infinitesimally thin beam or plate with a finite surface density and
>>speed of sound will be infinitely floppy.
>
>Err. Ok then. Very thin. (On the order of atomic radius thicknesses).
Let's see. IIRC, a beam with width W, length L, thickness t, and Young's
modulus E, can resist a bending force of EWt^2/L times a presumably small
dimensionless constant. The Young's modulus is proportional to the
density times the square of the speed of sound. If we combine the
formulas and let the mass be m and the sound speed v, we get mv^2t/L^2.
If we assume a beam 1 meter long, 10 centimeters wide, 1 angstrom thick,
massing 1 kilogram, and with a speed of sound c, then it can support
about 10 million newtons or 1000 tons (give or take a factor I can't
remember right now) if I did the arithmetic correctly.
Now for a sanity check. Let's assume a real material with a thickness
10^8 times greater and a sound speed 10^5 times slower. It should support
10 tons. That sounds high (1 ton sounds more realistic) but not absurdly
so once we take all the dimensionless constants into account.