Subject: Re: Hermeneutics and the difficulty to count to three...
From: meron@cars3.uchicago.edu
Date: Sat, 9 Nov 1996 18:46:28 GMT
In article , moggin@nando.net (moggin) writes:
> If observation is your only source of knowledge, and you can't
>observe the element decay, then the premise that the element isn't
>stable goes in the trash, and the example become meaningless.
Really? This would mean that any calculation ever done dealing with a
hypothetical case not yet observed in nature is pure trash. Rather
broad and sweeping statement, don't you think. In a way you got more
extreme than I'm here, I'm only saying that you can't attach physical
meaning to the unmeasurable, but you argue that even thinking about it
is trash. Nah, I suggest we avoid extremes.
.Now,
>if you _can_ observe it decay, that's fine -- but then you don't
>need to make any assumptions, and again the example is meaningless.
>You bring up another possibility -- that you can _predict_ it will
>decay; but that's knowledge several steps removed from observation.
>And by the time you start using predictions to classify things --
>well, you could be halfway across Wyoming, if you were in a car.
May I point that predictions is exactly one of those things science
deals with most of the time. Pretty successfully, too.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
Subject: Re: Sophistry 103 (was: I know that!)
From: weinecks@mail2.sas.upenn.edu (Silke-Maria Weineck)
Date: 9 Nov 1996 20:17:00 GMT
Richard Harter (cri@tiac.net) wrote:
: weinecks@mail2.sas.upenn.edu (Silke-Maria Weineck) wrote:
: >Richard Harter (cri@tiac.net) wrote:
: >: weinecks@mail1.sas.upenn.edu (Silke-Maria Weineck) wrote:
: >: >I'm afraid you couldn't; distorting the quote won't help. Derrida
: >: >corrects "constant" to "center" -- and if you want to understand the
: >: >sentence, you will have to know what "center" means in the context of
: >: >Structure, Sign, and Play. Which means you'll have to, gasp. read it.
: >: Please, he does no such thing; the correction is from "center" to
: >: "game".
: >I beg your pardon: "The Einsteinian constant is not a constant, is not a
: >center." (Structuralist Controversy, p. 267. Later, the paraphrase is not
: >of center for game, but of "_not_ a center" for "concept of the game."
: Well, lets see: Hyppolites question ends:
: And in that connection we see a
: constant appear, a constant which is a combination of space-time,
: which does not belong to any of the experimenters who live the
: experience, but which, in a way, dominates the whole construct;
: and this notion of the constant -- is this the center?
: And Derrida replies:
: The Einsteinian constant is not a constant, is not a center.
: It is the very concept of variability -- it is, finally, the
: concept of the game. In other words, it is not the concept of
: something -- of a center starting from which an observer could
: master the field -- but the very concept of the game
: In the first sentence Derrida says, three things very straight
: forwardly:
: (1) The Einsteinian constant is not a constant (as he is using the
: term).
: (2) The Einsteinian constant is not a center (as he is using the
: term).
: (3) The Einsteinian constant is the concept of the game.
: This is in reply to Hyppolite who asks if the Einsteinian constant is
: a center where "Einsteinian constant" is ostensibly defined by
: Hyppolite. Hereafter, for convenience, I will use "boojum" for
: "Einsteinian constant".
: Now you said: Derrida corrects "constant" to "center".
: And I said: Derrida corrects "center" to "game"
: Now I should have said "concept of the game" because those are the
: words that Derrida used. Other than that the essence is that H.
: propose the erroneous proposition that a boojum is a center and D.
: corrects his error, saying a boojum is the concept of a game.
: Nowhere in this exchange does D. correct "constant" to "center"
: unless, perhaps, he is correcting himself, i.e., he meant to say
: "center" and first said "constant". If it is your contention that he
: was correcting himself and that was what your point was addressing
: then (a) your remark was highly tangential and (b) it was quite
: misleading. I don't suppose that you meant any such thing, merely
: that that interpretation is the only thing that fits in with his
: remarks.
That's exactly what I meant, and I respectfully submit to your scrutiny
the claim that something the most important things happen on tangents
(or, as we litcritters are fond of saying, "in the margins"). I'm sorry
it mislead you --- Derrida hadn't engaged the notion of "constant" in his
talk, and he is trying to tell Hyppolite that constantia isn't at stake
here, but centritude (nice word, eh)? So he is correcting both himself
(that is precisifying himself) and Hyppolite.
: Without going into what D.'s "constant" and "center" are, there is a
: clear implication in the text that the "center" must be a "constant"
: which makes sense in view of the suggested role of the "center" in the
: "game". Since two different terms are used we may likewise assume
: that the intended meanings differ in some wise.
I disagree; centers do not have to be constants at all; that's part of
the point of the essay. And not every constant need to be a center, even
though it would have that potential, I suppose. The first point is
already clear in L-S (as discussion in other thread has shown), and
Derrida radicalizes it a bit.
: Of course you may have had some interpretation in mind that has
: escaped me. I may have missed the obvious. Feel free to beat me
: about the head and shoulders with it.
Dandruff?
: >I will play this game with you as well: what does Derrida mean by center?
: >What does he mean when he says that "the Einsteinian constant" is "not a
: >center"? Not a center of what, for instance? If, as you say, the sense is
: >"quite clear," this will be child's play. I do however caution you
: >against using a concept of center that is not in keeping with the one
: >Derrida alludes to in the essay.
: Why, I would imagine that it is the concept of something starting from
: which an observer could master the field. I don't suppose that that
: is all that a center is, not at all, but that much seems straight
: forward to me and is, after all, what the man said. The point is, he
: is explaining why a boojum is not a center and that is the reason he
: gave; it is consistent with the idea of a field being a game. I
: didn't claim that one could deduce what D. meant by a center from a
: single passage, merely that the relevant meaning within the context
: was clear.
I don't think so; the center is often introduced in retrospect, as L-S's
project shows -- it comes _after_ mastery, even though the question of
logical vs. temporal precedence is tricky here. The center, in other
words, is not necessarily a rule, even though it can be a rule. The whole
thing is not about mastering physics, though. I think Mati and I have
come a lot closer to what's at stake in some other thread -- the question
of whether knowledge can still be experienced, in short.
: > Perhaps my
: >: analysis was faulty; perhaps not. It is hard to say because it was
: >: simply ignored. And that has been the fairly consistent fate of any
: >: serious analysis in these discussions - it is ignored. Instead the
: >: snidery's work overtime.
: >: I find this a bit frustrating
: >You know, I found my daughter Stella on the phone one day; I asked
: >her whom she was calling, and she said, "the lady who tells you to hang
: >up and try again.
: Chortle. If you are saying that my little forays into pseudo
: intellectualism have no audience and that I am not entirely swift in
: not perceiving this, why, I can appreciate that. But if you are
: contending that all efforts at intelligent discourse reach the lady
: who tells you to hang up and try again, why I would be far from
: arguing with you. Saddened perhaps, but the evidence is with you.
Ah, you think the worst of me; it was quite to the contrary; I was
identifying with Stella and her perseverance in trying to reach someone
in the face of much resistance. I'm fiddling with the phone number.
Silke
:
: Richard Harter, cri@tiac.net, The Concord Research Institute
: URL = http://www.tiac.net/users/cri, phone = 1-508-369-3911
: Life is tough. The other day I was pulled over for doing trochee's
: in an iambic pentameter zone and they revoked my poetic license.
Subject: Re: When will the U.S. finally go metric?
From: mlyle@scvnet.com
Date: 9 Nov 1996 20:07:23 GMT
Paul Skoczylas wrote:
>Markus Kuhn wrote:
>>
>> Paul Skoczylas wrote:
>>
>> > metre - m
>> > joule - J
>> > newton - N
>> > pascal - P
>> > second - s (not sec. in SI)
>>
>> Just a minor correction here:
>>
>> pascal - Pa (newtons per square meter pressure, 100 kPa is very
>> close to typical sea level athmospheric pressure)
>>
>
>Well, I feel sheepish. (Baa!) Of course it's Pa. (I assure you it was
>simply a typo on my part.)
OK, the above is true, but _why_ is the abbreviation "Pa" instead of "P"?
Is there another unit I've overlooked that is abbreviated "P"?
It seems that the SI, which is a quest for consistant units, has really
dropped the ball when it comes to abbreviations. The selection of names
with the same first letters (Henry, Hertz, Watt, Weber) increases the
chance of error. Yes, it's nice to honor scientists, but not by making
everyone's lives more difficult!
Multiplier prefixes are another source of confusion. Why on earth aren't
"da- (10^1), h- (10^2), and k- (10^3) capitalized as are all the larger
multipliers? This would not interfere with the lesser multipliers (we
would even be able to removed the "a" from "da", the only 2-letter
prefix!) and would make the prefix system more consistant.
Then there's those Greek letters that snuck into the system. We could
use "O" for "Ohm" and "i" for "micro-" (m is "milli-") without messing
anything else up.
Oh to have been there when they were designing this system!
George Lyle
Subject: Re: What is the Cause of Time Dilation?
From: odessey2@ix.netcom.com(Allen Meisner)
Date: 9 Nov 1996 23:43:45 GMT
In <562gec$k2k@sjx-ixn7.ix.netcom.com> bjon@ix.netcom.com (Brian Jones)
writes:
>
>Christopher R Volpe wrote[in part]:
>[snip]
>[bjon]
>>> Let's see, how can I put this? We do not have absolute time at our
>>> disposal, but it does of course exist.
>
>[Volpe]
>>Proof by blatant assertion. It is meaningless and vacuous to assert
the
>>existence of that which cannot be detected ever, even in principle.
>
>As in "no absolute motion exists" meaning that SRT is not a testable
>theory?
>
>>> We just can't use it.
>>> Although each and every clock has an actual intrinsic "beat," we
have
>
>>That actual and intrinsic beat is called proper time, It has nothing
to
>>do with the notion of absolute time.
>
>It is the abolute time as recorded by an actual, real clock, and is
>not observer-dependent, so I have no idea what definition of
>"absolute" you're using.
>
>>> no way of knowing or determining what this actual beat may be.
This
>>> is because WE slow down with the clock. =
>
>
>>In much the same way that we physically contract the x-extent of the
>>fishing rod to fit it in the trunk.
>
>Hawgwarsh. What has this to do with the actual beat of actual time?
>
>>> When you say "absolute time,"
>>> it usually means "We possess it and can use it,"
>
>>No, when we say "absolute time" we mean "time spans between spacetime
>>events that are not dependent on the inertial frame in which those
spans
>>are measured". It has been physically demonstrated that this kind of
>>time does not exist in our universe, because any consistent means of
>>measuring time will give different answers to the question of time
>>separation of spacetime events when measured from different inertial
>>frames.
>
How about the time span between spacetime events that are dependent
on an inertial frame that is at absolute rest? Would this give us the
absolute time?
>
>>> and this is obviously
>>> not true, so I agree with you that we don't "have" it. But it does
>>> have a very real existence as shown by the actual beat of each
atomic
>>> clock.
>
>>The actual beat of an atomic clock demonstrates the notion of proper
>>time. The fact that atomic clocks in different inertial frames will
beat
>>at different rates demonstrates that time is not absolute. All you
are
>>doing is showing that "time exists". You have demonstrated nothing
about
>>"absolute time".
>
>Merely labeling something as "proper time" does not change the fact
>that it is a real (nonrelative) clock time per a real clock. This is
>what I mean by saying that it's absolute.
>
>>> >The invariant interval *is* proper time!!! The interval in
question is
>>> >the space-time interval between two events. Note that in the
coordinate
>>> >system in which an observer moves inertially between two events in
>>> >space-time, the two events take place at the same location (by
>>> >construction, each event occurs at location (0,0,0), i.e. the
origin, of
>>> >the observer's spatial coordinate system). Since they take place
at the
>>> >same location in this system, the invariant interval has only a
temporal
>>> >aspect in this system. The entire spacetime interval is a time
interval
>>> >in this coordinate system, and we call this time interval "proper
time".
>
>>> >"Spacetime interval" between two events is synonymous with the
proper
>>> >time experienced by an observer moving inertially from one event
to the
>>> >next.
>>>
>
>>> >Chris Volpe
>>>
>
>A real clock (the only way to get a real proper time) cannot move
>between all possible events (some are too far apart spatially), but
>there's still a perfectly valid invariant interval for such events.
>
>>> The invariant interval (II):
>>> Observer A finds two events to be 1 LY and .0583 Yr apart.
>>> Observer B finds the event to be 1.4364 LY & 1.0328 Yrs apart.
>>> =
>
>>> A's II=B2 =3D (1 LY)=B2 - (.0583 Yr)=B2 =3D .9966
>>> B's II=B2 =3D (1.4364 LY)=B2 - (1.0328 Yrs) =3D .9966
>>> =
>
>>> What physical meaning is there to the .9966 result? It is a
>>> combination of distance and time, each squared. =
>
>
>>First, you forgot that the time component is multiplied by the speed
of
>>light, or, alternatively, the distance component is divided by it.
>>Usually, it is convenient to work in units where c=3D1, but this
doesn't
>>change the fact that we need the c factor if only to preserve units.
=
>
>
>>Given a right triangle with two legs of length A and B, what is the
>>physical meaning of A^2+B^2? It is a combination of lengths squared.
>
>>> What meaning can
>>> a time squared have? =
>
>
>>What meaning can a length squared have? (Hint: In the right triangle
>>case, you have to remember to take the square root to get the
invariant
>>length of the hypotenuse. In the case of the spacetime coordinates,
you
>>have to take the square root to get the spacetime interval, which
gives
>>you the proper time of an observer moving inertially between the two
>>events.
>
>>>And what about subtracting this time squared
>>> from the distance squared?
>
>>I addressed that two paragraphs up. There's a missing c factor in
there
>>that corrects the units.
>
>>> =
>
>>> OTOH, the proper time for the two events is the time recorded by a
>>> single clock that happened to be at each event (by moving between
>>> them).
>
>>By moving *inertially* between them. And as I already pointed out,
the
>>invariant spacetime interval gives this value. But you weren't paying
>>attention, as usual.
>
>
>>> This value depends on how fast the clock had to go, which in
>>> turn depends upon how far apart the events were in space, and upon
the
>>> true time between them. =
>
>
>>No it doesn't. I don't need to know how far apart the events were in
>>your mythical fixed "space", nor do I need to know how much time
elapsed
>>on God's wall clock. All I need to know is the coordinates of each
event
>>in *any* inertial coordinate system. Once I know this, I can figure
out
>>how fast an observer must go, inertially, in my coordinate system
such
>>that he leavs the location of event A at the time of event A and
arrives
>>at the location of event B at the time of evvent B. And lo and
behold,
>>if I figure out the elapsed time on his clock based on the
relativistic
>>time dilation relative to mine at his velocity relative to me and the
>>time in my coordinate system between the two events, I'll get the
same
>>answer for his elapsed time as I would if I computed the invariant
>>spacetime interval.
>
>>>Obviously, for many events, there's not
>>> enough time for a clock to "span" them, even at lightspeed, so
there
>>> would be no proper time for the events. This is the case above.
>
>>???
>>--
>
>>Chris Volpe Phone: (518) 387-7766 =
>
>>GE Corporate R&D; Fax: (518) 387-6560
>>PO Box 8 Email: volpecr@crd.ge.com
>>Schenectady, NY 12301 Web: http://www.crd.ge.com/~volpecr
>
>
Subject: Re: Do gravitational waves carry momentum? was: Does gravitational waves carry momentum
From: kfischer@iglou.com (Ken Fischer)
Date: Sat, 9 Nov 1996 23:33:33 GMT
Gordon D. Pusch (pusch@mcs.anl.gov) wrote:
: In article kfischer@iglou.com (Ken Fischer) writes:
: > I found something on page 719 [MTW] that really
: > discourages me. It is something about gravitational
: > radiation being not being required if the expansion of
: > the universe is homogenous and isotropic.
: I think you're misinterpreted these passages. Unless you own a
: different edition of [MTW] than I do, p.719 says =NOTHING= about
: gravitational radiation --- it is a rebuttal of the mistaken notion
: that if ``the Universe'' expands, then EACH and EVERY individual ATOM
: in it must ``expand'' as well, rendering the expansion unobservable.
: Your next paragraph adds weight to this:
You are correct, what I stated above is on page 730,
I should have said page 719 and thereafter concerning the
expansion of the universe.
When I started the followup article, I had just
noticed the part about a general expansion, and I was
discouraged, as I said.
But the discussion did help me a great deal,
it pointed out to me that the author apparently only
considered a general expansion that was coasting from
a time when energy and matter decoupled (or sometime
around then).
I do not suggest that there is a general
isotropic expansion, I propose that there is an
accelerated expansion of matter, but a coasting
expansion of the universe (the recession of the
galaxies, not an expansion of space itself, space
has no intrinsic properties except that matter
extends into space).
I apologize for not stating the coorect
page for each statement.
: > I haven't fully digested it yet, but it is
: > another case of finding GR has already considered the
: > possibility of matter expanding, but, the authors dismiss
: > the idea in a single sentence, only on the basis that if
: > the expansion was general all the way down to sub-atomic
: > scales, there would be no way to detect or measure it,
: > at least that is the way I interpret what is said at first
: > read.
: Yes, that is =exactly= MTW's point --- that since the sub-constituents of
: matter experience =OTHER= forces in ADDITION to the ``apparent forces''
: induced by the time-variation of the cosmological background metric,
I think the statement was clear on page 719, the author
states that there is no expansion of the Earth-Sun distance, etc.
And I beg to disagree.
: [snip]
: > I concede that _if_ the expansion is like a balloon
: > with the galaxies represented by pennies glued on it's surface,
: > then there has to be gravitational radiation.
: > Unfortunately, I am of the opinion that the galaxies
: > also expand, and that all matter itself expands, due to quark-
: > quark repulsion.
: There is no experimental evidence supporting a ``quark-quark repulsio
: in fact, the experiment evidence suggests a rubber-band-like
: =ATTRACTION=
: between any aggregate of quarks that do not have a net ``color-neutrality.
: (BTW, protons, neutrons, electrons and all other long-live particles are
: net color-neutral...)
Can you pleas answer one question for me, the
texts do not appear explicit to me. Are electrons
composed of quarks?
I do not want anyone to mistakenly think I know
what I am talking about. I do not disagree with GR.
Perhaps you haven't noticed where I stated I
only study gravity, and I am trying to explore a model
of gravitation based on the expansion of matter, and
I have no intention of trying to pass off my model as
mainstream physics.
: > I don't enjoy the prospect of promoting a model that excludes
: > gravitational radiation, at least I think it does, and it seems that
: > MTW says the same thing, but they dismiss the model on a "if it
: > were, we couldn't tell, so it isn't" basis (I suspect there was more
: > thought put into it than that, but I haven't read any more about it).
: And IMO, even what you read, you misunderstood... :-(
I guess it looked that way, unless page 730 is
connected in a rational way with page 719.
: [snip]
: > : > In Newtonian gravitation, a rock pushed off a cliff
: > : > accelerates until it hits the ground below. According
: > : > to the definition of binary stars producing gravitational
: > : > radiation, it would seem that a rock pushed off a cliff
: > : > would produce gravitational radiation, at the speed of
: > : > light, and a detector on the ground below should receive
: > : > the gravitational radiation before the rock hits.
: > : > The nearness of the rock, even though it's mass
: > : > is small, should produce a greater flux for the detection
: > : > of gravitational radiation than binary stars many light
: > : > years away.
: >
: > : Do the calculation. If the flux is as strong as you think it is,
: > : then why is everyone trying to detect astrophysical sources of
: > : gravitational waves?
: >
: > Well, i g is much of an acceleration, but large
: > artillery shells are designed to withstand 50,000 g's,
: > and railguns might provide a decent accelerating mass.
: > I assume the flux would have to follow the inverse
: > square rule.
: === DO THE CALCULATION === !!!!!!! You'll find that gravitational
: radiation will not become appreciable until the accelerations approach
: the surface-gravity of a neutron-star --- i.e., tens of ===BILLIONS===
: of g's !!! Gravity-waves *sneer* upon the pitifully small acceleration
: that human-built ``railguns'' produce --- after all, such guns are made
: out of mere ``ordinary'' matter, not neutronium... :-/
Things must have changed since Joe Weber's prize
winning essay around 1960, ay least I got the impression
when I read it that it might some day be possible to
generate gravity waves in the laboratory, and build
devices to detect them.
: [snip]
: > I have to insist (and it seems that page 719 concurs)
: > that if the expansion were general at all scales, gravitation
: > would produce a geometrical pseudo-field which would not require
: > gravitational radiation.
: *Bzzzzzttt!* Sorry, you're wrong --- but thanks for playing!
: Better read at least ``track one'' of [MTW] a few more times, and
: rather more carefully; you still don't understand what it *means* yet
: --- even on a qualitative level (not that Wheeler's =APPALLINGLY= bad
: prose helps, much... :-( I =also= recommend that you work through
: at least a few of the relevant exercises...
I am not interested in the study of General Relativity,
I am hoping someone (or a lot of people working together) will
discover or prove how gravity works.
I am not interested in being right or wrong, I only
want to understand gravity.
Wheeler's, or whoever wrote certain passages in the
book, writings would be great for lectures, then all the
possibilities presented could be sorted out, and definite
statements could be made that clearly say what is not true.
But the same style, in my opinion, is in Spacetime
Physics, it forces the student to think, which is good,
but if the reader doesn't read the whole chapter, they
could possibly get the wrong idea.
: Finally, if your bookstore doesn't carry Ohanion's text, might I
: suggest that you employ __Inter-Library Loan__ to obtain a copy ???
: You don't have to *buy* the bloody thing in order to _read_ it,
: ya know... :-/
Thanks for the suggestion, I think I will be able
to order a copy to buy shortly.
And thanks for pointing out I had the wrong page.
Ken Fischer
Subject: Re: Do gravitational waves carry momentum?
From: Peter Diehr
Date: Sat, 09 Nov 1996 16:16:08 -0500
Ken Fischer wrote:
>
> Nathan M. Urban (nurban@csugrad.cs.vt.edu) wrote:
> : In article , kfischer@iglou.com (Ken Fischer) wrote:
> : > In General Relativity, freefalling objects move
> : > along geodesics in spacetime, and they move in inertial
> : > motion (are _NOT_ accelerated), but everybody says they
> : > are accelerated.
> : > Bodies in orbit move in inertial motion, yet
> : > everybody says they are accelerated.
>
> : Relativists don't say they are accelerated.
>
> I trust an explanation follows.
>
The acceleration is in 3-space, which is what we see. But the geodesics are
in 4 dimensional spacetime, and following a geodesic is the _definition_ of
not being accelerated. Thus you can eat your cake (in 3 space) and have it
(in 4 space) too!
> : > Gravitational radiation is supposedly a prediction
> : > of General Relativity. In General Relativity, stars
> : > in orbit around each other are _NOT_ accelerated (in
> : > Newtonian gravitation they are).
> : > So I am at a loss to understand how binary stars
> : > in orbit around each other produce gravitational radiation
> : > ( I must be a little stupid, maybe a lot :-), because
> : > someone said two people received a Nobel prize for
> : > their study of the effects of the gravitational radiation).
>
> : It's not a stupid question, your objections are quite natural. Yet
> : gravitational radiation is consistent with general relativity and the
> : equivalence principle.
>
I like your question, Ken! I'll have to think about it for a while, and
do some research.
> I found something on page 719 [MTW] that really
> discourages me. It is something about gravitational
> radiation being not being required if the expansion of
> the universe is homogenous and isotropic.
But of course it is not isotropic and homogeneous except on the
very largest, very coarse scale of clusters of galaxies. In the
discussion, MTW devote most of a page to showing how this is an
unrealistic model. The point, I guess, is that the expansion
itself results in some gravitational radiation due to lack of
isotropy and homogeneity. But if everything were truly uniform,
then the expansion itself would not lead to any gravitational
radiation.
> I haven't fully digested it yet, but it is
> another case of finding GR has already considered the
> possibility of matter expanding, but, the authors dismiss
> the idea in a single sentence, only on the basis that if
> the expansion was general all the way down to sub-atomic
> scales, there would be no way to detect or measure it,
> at least that is the way I interpret what is said at first
> read.
Hopefully my comments will lead to a reconsideration on your
part.
> I consider surface gravity to be a pretty good clue.
>
And as you already know, I am certain that your idea is fatally
flawed. But this isn't the forum to discuss that, I think.
> : But the conditions for radiation are interesting. The naive "it's
> : accelerating so it must radiate" condition is not sufficiently
> : precise. It turns out that mere geodesic deviation is not sufficient.
> : Ohanian says that it is produced by a time-varying stress-energy
> : distribution, which makes sense from the above argument. Yet
> : "time-varying" in GR automatically causes problems. If you are in flat
> : spacetime, a particle moving at constant velocity will have a
> : time-varying stress-energy distribution from your point of view, but
> : will not, of course, from its own. So that's not a precise
> : characterization of the conditions. What you really need is a
> : gravitational quadrupole moment; that can't be transformed away using
> : the equivalence principle.
>
> But the time-varying part interests me.
>
I would interpret that as a simple requirement that the object must
encounter a varying tensor along its spacetime path ... the variation
would thus be wrt its proper time.
> : quite significant if it's a large detector. I think that things like
> : LIGO work better with approximately planar gravitational waves.
>
> I really expected spherical wavefronts, I don't
> know what you mean.
>
As you move away from the center of spherical radiation, the wave fronts
look more and more like plane waves to the observer of finite extent.
Just like the surface of the earth looks pretty flat to a farmer.
Best Regards, Peter
Subject: Re: Time & space, still (was: Hermeneutics ...)
From: +@+.+ (G*rd*n)
Date: 9 Nov 1996 18:07:42 -0500
meron@cars3.uchicago.edu (Mati):
| >| Also, I'm not sure what you mean by "it became orthodoxy". It was
| >| used since it worked. Mind you, Newtonian gravity is a formula, not a
| >| theory. There is no explanation of any sort offered. So, how does a
| >| formula become an orthodoxy?
+@+.+ (G*rd*n) writes:
| >Curiously, this is where I came in, so long ago. I
| >complained about the reification or materialization of the
| >law of gravity, and the howling began. How does it become
| >not only an orthodoxy, but a True Faith involving a kind of
| >incarnation or transubstantiation? This is precisely the
| >question I've been asking.
meron@cars3.uchicago.edu:
| Sounds like "when did you stop beating your wife?" to me.
C'mon, if people are claiming that a theory of gravity is
materially inherent in phenomena _we_ collect and objectify
as "gravity", they are, to me, proclaiming the incarnation
(embodiment) of a _human_ abstraction. And if they become
greatly wroth with unbelievers, then I take their passion to
be religious, since what excites them is a question of faith
in what's really real, the Truth, etc. etc. etc.
--
}"{ G*rd*n }"{ gcf @ panix.com }"{
Subject: Re: Time & space, still (was: Hermeneutics ...)
From: meron@cars3.uchicago.edu
Date: Sat, 9 Nov 1996 19:58:45 GMT
In article , moggin@nando.net (moggin) writes:
>meron@cars3.uchicago.edu (Mati):
>
>> >> [...] One of the originators
>> >> of the "least action" approach (an extraemly important part of physics
>> >> but I won't get into details now), either Maupertois or Fermat (or
>> >> maybe even both of them), was motivated in his work by theological
>> >> notions. So, if somebody reads his rambling on the subject and
>> >> considers them to be part of the his contribution to physics, one may
>> >> conclude something like "one of the centerpieces of physics is based
>> >> on religious mistycism". Which ain't true, although that founding
>> >> father really thought so.
>
>moggin:
>
>> > Well, _one_ of them is -- as I've mentioned before, Newton
>> >imported his concept of action-at-a-distance to physics from his
>> >studies in hermetic philosophy (read: religious mysticism). The
>> >reaction from his colleagues was just what you would expect: they
>> >felt it was poppycock. But when the dust settled (as one might
>> >say), it had become orthodoxy, and it stayed that way for several
>> >hundred years.
>
>Mati:
>
>> I don't know if you did read the excerpt from Principia that somebody
>> (I think either Weiss or Siemons) posted here few days ago. Newton
>> writes there about gravity and clearly states that he has no
>> explanation for its action and not going to try to offer one since
>> (I'm not using his words here, only paraphrasing them, maybe somebody
>> will repost) offering hypotheses which can't be verified isn't the job
>> of a scientist. Doesn't strike me as introducing a mystical idea,
>> rather stating "that's the way it works, though we don't know why".
>
> Missed the excerpt, or read it too quickly. I agree that what
>you're saying here isn't mystical, but I was referring to the concept
>of action-at-a-distance, which Newton introduced to explain the way
>that gravity worked -- in other words, to provide a means by which it
>could exert its force. Action-at-a-distance is mystical in that it
>comes from hermeticism, and also in the rather ghostly quality which
>it has, as an idea. But as an explanatory principle, it's empty, I
>think, more than it is mystical -- really, it just begs the question.
The point of the excerpt I've mentioned is that Newton didn't
introduce action at a distance as explanation for gravity. He just
stated that it appears to act from a distance and the he has no
explanation. Was quite explicit about having no explanation, in fact.
>
>> Also, I'm not sure what you mean by "it became orthodoxy". It was
>> used since it worked.
>
> Wait a minute -- you just finished telling me it didn't exist.
>
Gravity didn't exist???!!!
>> Mind you, Newtonian gravity is a formula, not a theory. There is no
>> explanation of any sort offered. So, how does a formula become an
>>orthodoxy?
>
> That's a different question, and I'd like to stick with this one,
>for now. Action-at-a-distance _is_ the explanation that Newton gave,
>and the one that eventually became accepted, after the resistance died
>down, even though it meant introducing sheer mysticism into physics.
No, read above.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
Subject: Re: Universal Coordinate System
From: odessey2@ix.netcom.com(Allen Meisner)
Date: 9 Nov 1996 23:54:40 GMT
In <3283D619.393E@mail.ic.net> Peter Diehr writes:
>
>Allen Meisner wrote:
>>
>> One can establish an universal coordinate system by arbitaririly
>> picking an absolute reference frame. This is done with a navigation
>> buoy that consists of three lasers perpendicular to each other such
>> that they form the x,y,z coordinate axis. You then go out in a
>> spaceship. A laser beam is shone in all directions. If the light
bends
>> in any of the directions, the velocity of the ship is adjusted so
that
>> none of the beams is deflected. The spaceship is now at absolute
rest.
>> The navigation bouy is released and now represents the origin of the
>> universal coordinate system. All the planets' and stars' and
galaxies'
>> absolute velocities are then mapped with respect to this univeral
>> coordianate system. If you are traveling in space you determine your
>> velocity relative to the stars or planets or galaxies. Since the
>> absolute velocities of these are known with respect to the universal
>> coordianate, the absolute velocity of the spaceship can be
determined
>> wrt the absolute coordinate system.
>>
>> Edward Meisner
>
>
>While this is a reasonable system for navigation, it is still still a
>relative coordinate system: the ship measures its position with
respect
>to (relative to) the buoy.
>
>You can easily verify this by releasing a second buoy: navigation
proceeds
>as before, and one can arbitrarily name buoy 1 or buoy 2 as the
"absolute
>system" ... they are identical in function, but yield different
coordinates.
>
>Best Regards, Peter
Yes, that is why I said "arbitrarily" choose an absolute coordinate
system. However, both buoys are still absolute reference frames by
which absolute velocities can be measured. I don't know exactly what
the Lonrentz transforms are, but I would imagine you could use them to
get the correct absolute velocties by inference from one frame to
another.
Regards,
Edward Meisner
Subject: Re: Our current education system (was Re: How Much Math? (not enough))
From: nanken@tiac.net (Ken MacIver)
Date: Sun, 10 Nov 1996 00:43:26 GMT
gonser@eawag.ch (-Tom-) wrote:
>turpin@cs.utexas.edu (Russell Turpin) wrote:
>> >> Maybe we can get topology made a high-school course? (Oh ...,
>> >> what *am* I thinking?!)
>>
>> Candy:
>> > Actually, there is a non-negligible fraction of students who
>> > would both enjoy and benefit from this.
>>
>> I agree. My expressed frustration is not with the innate
>> value of the notion, but with the silliness of thinking about
>> such things in the context of our current educational system.
>What do you think makes the current educational system so bad?
>How would you suggest we improve it?
>I find the poor state of American public education is an expression or
>symptom of much deeper and wide-spread deficiencies in the appreciation of
>learning and the educated in general.
>Over here in German-speaking Europe education is highly esteemed, teachers
>and especially professors are greatly respected and society offers
>teachers tremendous benefits and job security to attract the bright and
>select only the best to teach its youth. Universities are free in order to
>offer everyone that qualifies regardless of parents' income equal
>opportunity. Society shows a strong commitment to see to it that everyone
>(not just my own kids) gets a good education.
There is some truth to this, I think. However, in Germany (& most
other European countries, I believe), kids are weeded out quickly,
thos who don't make the grade are moved out into society or to a
technical school at a younger age, and the system concentrates its
resources on the select - i.e. those who attend the Gymnasium, for
example, in Germany.
>In the US, on the other hand, the general attitude is _very_ different.
>Scientists are stereotyped as nerds, huge portions of the population are
>ignorant of what's going on in the world, teachers and education are often
>treated with disrespect down to downright contempt, there is no incentive
>whatsoever to become a teacher short of pure idealism, and a social
>attitude permeates society that sends the message to its youth: We don't
>care about your higher education. If you want it, get it yourself!
This is both true and false. It is true that Americans as a group
devalue in particular humanities, art, philosophy, and the like and
often place on mindless pedestal science and other things that promise
*answers*. I have a pretty good imagination, yet I'd find it hard to
imagine an American scence such as that in one of Zola's novel where a
working class wedding party takes a tour of the Louvre.
OTOH, Americans have an almost indecent obsession about higher
education, to the point of touting it without focus, lowering or
eliminating admissions barriers, and offering easy access to loans
that may encumber the students for a decade or more, dampening an
other wise youtful propensity towards risk taking and exploration.
Ken
Subject: Re: HELP ME PLEASE!!!!!!!! High School Design Problem (trivial, difficult and now annoying)
From: "\"Alan \\\"Uncle Al\\\" Schwartz\""
Date: 8 Nov 1996 17:44:12 GMT
artiste@pathcom.com (T. Sloan) wrote:
>Hi there,
>
> A couple of weeks ago, our prof. by some outworldly motivation,
>assigned the term design and thesis:
>
>* Build a buggy of mass<250g, powered by rubber bands and cabable of pushing a
>mass00g of specified distances of up to 6.5m.
>
>How the hell do I do this!!!!! In theory, it should work (according to >our prof.), but with a mass of 300g (weight<3N), the lim. static >friction to overcome is a bit of a nuisance, especially with a car where >the bands spin out extremely fast.
>This of course required me to put on wheels with a greater mass, and >better traction (I used a roller blade wheel, 72mm, 78a hardness). The >earlier wheels just spun out, and the mass + car moved nowhere.
[snip]
OK, so the power is cool but the traction is lacking.
If you are on a fibrous or porous surface, glue coarse grit or tiny
cleats (like the tear line on plastic wrap packages) to the wheels. You
must grab without seizing.
If you are on a slick surface like linoleum, think about drag racing
before the car pulls up to the Christmas tree.. A thin (replaceable)
layer of very low durometer rubber on the wheels will have tremendous
friction without adhesion. A thin layer of well-dried rubber cement
might do it.
I had a problem where large alumnum trays were being used to ferry lenses
and prescription blanks. Everytime the trays were tilted or bumped the
stuff scrambled. The tray surface had to be sanitary (like it made a
difference). I dissolved a very low durometer polyurethane (I think it
was around 10) in dichlormethane and laid down about 2 microns on the
aluminum. It held to the aluminum like a banker touching gold, and had a
huge coefficient of friction - things would not slide until a 50 degree
angle or more. It wa easily swabbed with alcohol to clean it, and was
not at all sticky.
--
Alan "Uncle Al" Schwartz
UncleAl0@ix.netcom.com ("zero" before @)
http://www.ultra.net.au/~wisby/uncleal.htm (lots of + new)
(Toxic URL! Unsafe for children, Democrats, and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Subject: Re: Time & space, still (was: Hermeneutics ...)
From: meron@cars3.uchicago.edu
Date: Sat, 9 Nov 1996 23:43:47 GMT
In article <5632ru$dc3@panix2.panix.com>, +@+.+ (G*rd*n) writes:
>meron@cars3.uchicago.edu (Mati):
>| >| Also, I'm not sure what you mean by "it became orthodoxy". It was
>| >| used since it worked. Mind you, Newtonian gravity is a formula, not a
>| >| theory. There is no explanation of any sort offered. So, how does a
>| >| formula become an orthodoxy?
>
>+@+.+ (G*rd*n) writes:
>| >Curiously, this is where I came in, so long ago. I
>| >complained about the reification or materialization of the
>| >law of gravity, and the howling began. How does it become
>| >not only an orthodoxy, but a True Faith involving a kind of
>| >incarnation or transubstantiation? This is precisely the
>| >question I've been asking.
>
>meron@cars3.uchicago.edu:
>| Sounds like "when did you stop beating your wife?" to me.
>
>C'mon, if people are claiming that a theory of gravity is
>materially inherent in phenomena _we_ collect and objectify
>as "gravity", they are, to me, proclaiming the incarnation
^^
>(embodiment) of a _human_ abstraction.
Too complicated for me, try to use simpler language. Anyway, what
people are claiming is that if you use the formula
F = G*m_1*m_2/r^2
to calculate the force of gravity between two material objects and
then use the result as the force in Newton's F = ma, you get
predictions for trajectories which match well with observations (all
the above valid for classical physics, in GR the mathematical
formulation is different). That's all. Got it. That's all!
Whatever meanings you attach to it, whatever images it conjures in
your imagination, this is your business, having nothing to do with
science.
>And if they become
>greatly wroth with unbelievers, then I take their passion to
>be religious, since what excites them is a question of faith
>in what's really real, the Truth, etc. etc. etc.
Science doesn't deal with Truth and, as was already pointed to you, it
doesn't demand more faith in what's really real then what you need to
cross the street. Lets face it, this bogeyman of science as religion,
proclaiming the Truth and pursuing the nonbelievers is an image you've
created for yourself, no more than this. And now you're fighting
against a figment of your imagination. Well, have fun and count me
out.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
Subject: Re: Time & space, still (was: Hermeneutics ...)
From: cri@tiac.net (Richard Harter)
Date: Sun, 10 Nov 1996 01:17:04 GMT
weinecks@mail1.sas.upenn.edu (Silke-Maria Weineck) wrote:
>I'm not denying anything you said, but you are still missing the point;
>some people have pointed out here that when Heisenberg or Bohr or
>Einstein comment _philosophically_, they are not commenting qua
>scientists either, and that their "musings" or "thoughts" have no
>bearings on physics as it is of interest to Mati. They _do_ understand
>the physics but they also address questions that are _not_ pertinent to
>the practice of physics -- just like Derrida, perchance.
This is a substantial misrepresentation of what Mati was saying, oddly
enough the same one that Mammel was producing. Does this really have
to be explained?
>And I will repeat my recommendation: if you want to know whether Bohr and
>Derrida are really as far apart as you assume, refer yourself to
>Plotnitsky's _Complementarity_.
It is not likely that I will refer to Plotnitsky but, still, I
seriously doubt it. I have read to enough of Derrida to have a sense
of how he approaches things and enough of Bohr to know how he
approaches things and I do not believe. To be sure there are
commonalities, such can always be found. A raven is like a writing
desk, after all.
>I also find your comments a tad disingenuous -- by now it has been
>pointed out a million times that Derrida's comments on SR do _not_ spring
>out of a whole context of his work but are a casual reply to a casual
>question by a colleague -- in other words, yes, he's dabbling a bit --
>just as Bohr and Heisenberg etc. are dabbling in philosophy.
Bladderwort. I was not referring to that oft quoted exchange as a
topic and well you should know it. If you want to pick that
particular scab still do so in private, if you please, but do not
charge me with picking it for you.
Richard Harter, cri@tiac.net, The Concord Research Institute
URL = http://www.tiac.net/users/cri, phone = 1-508-369-3911
Life is tough. The other day I was pulled over for doing trochee's
in an iambic pentameter zone and they revoked my poetic license.
Subject: Re: Universal Coordinate System
From: Peter Diehr
Date: Sat, 09 Nov 1996 20:30:40 -0500
Allen Meisner wrote:
>
> In <3283D619.393E@mail.ic.net> Peter Diehr writes:
>
> >While this is a reasonable system for navigation, it is still still a
> >relative coordinate system: the ship measures its position with
> respect
> >to (relative to) the buoy.
> >
> >You can easily verify this by releasing a second buoy: navigation
> proceeds
> >as before, and one can arbitrarily name buoy 1 or buoy 2 as the
> "absolute
> >system" ... they are identical in function, but yield different
> coordinates.
> >
> >Best Regards, Peter
>
> Yes, that is why I said "arbitrarily" choose an absolute coordinate
> system. However, both buoys are still absolute reference frames by
> which absolute velocities can be measured. I don't know exactly what
> the Lonrentz transforms are, but I would imagine you could use them to
> get the correct absolute velocties by inference from one frame to
> another.
>
> Regards,
> Edward Meisner
A Lorentz transformation is a shift to a reference system moving at a
different relative speed: like the change from standing on an escalator
to standing on the floor.
There is nothing wrong with anything that you are saying _except_ that
everywhere you say "absolute" you should be saying "relative". It's a
matter of definition.
When previous generations of philosophers and scientists talked about
the aether, they meant the one absolute reference frame which was not
moving, period. Isaac Newton associated this with a theological speculation:
the absolute rest frame is coincident with the sensorium of God.
However, neither Newtonian mechanics, nor Relativistic theory requires
that such an absolute reference frame exist ... and relativity tells
us that one inertial reference frame is as good as any other to state and
or test the laws of physics.
Arbitrarily picking one out and calling it "absolute" serves no purpose.
Best Regards, Peter
Subject: Re: Sophistry 103 (was: I know that!)
From: cri@tiac.net (Richard Harter)
Date: Sun, 10 Nov 1996 01:29:39 GMT
weinecks@mail2.sas.upenn.edu (Silke-Maria Weineck) wrote:
>Richard Harter (cri@tiac.net) wrote:
>: Nowhere in this exchange does D. correct "constant" to "center"
>: unless, perhaps, he is correcting himself, i.e., he meant to say
>: "center" and first said "constant". ..
>That's exactly what I meant, and I respectfully submit to your scrutiny
>the claim that something the most important things happen on tangents
>(or, as we litcritters are fond of saying, "in the margins"). I'm sorry
>it mislead you --- Derrida hadn't engaged the notion of "constant" in his
>talk, and he is trying to tell Hyppolite that constantia isn't at stake
>here, but centritude (nice word, eh)? So he is correcting both himself
>(that is precisifying himself) and Hyppolite.
Even so. As a further tangent, the post to which you are responding
was sitting in my news reader unposted for several days and went well
out after composition. Sundry matters unclear to me at the time were
clarified inbetween times.
>I disagree; centers do not have to be constants at all; that's part of
>the point of the essay. And not every constant need to be a center, even
>though it would have that potential, I suppose. The first point is
>already clear in L-S (as discussion in other thread has shown), and
>Derrida radicalizes it a bit.
Understood.
[snip discussion of center]
>: > Perhaps my
>: >: analysis was faulty; perhaps not. It is hard to say because it was
>: >: simply ignored. And that has been the fairly consistent fate of any
>: >: serious analysis in these discussions - it is ignored. Instead the
>: >: snidery's work overtime.
>: >: I find this a bit frustrating
>: >You know, I found my daughter Stella on the phone one day; I asked
>: >her whom she was calling, and she said, "the lady who tells you to hang
>: >up and try again.
>: Chortle. If you are saying that my little forays into pseudo
>: intellectualism have no audience and that I am not entirely swift in
>: not perceiving this, why, I can appreciate that. But if you are
>: contending that all efforts at intelligent discourse reach the lady
>: who tells you to hang up and try again, why I would be far from
>: arguing with you. Saddened perhaps, but the evidence is with you.
>Ah, you think the worst of me; it was quite to the contrary; I was
>identifying with Stella and her perseverance in trying to reach someone
>in the face of much resistance. I'm fiddling with the phone number.
Oho, I misunderstood. When I reach that lady it usually that she is
telling me that I have the wrong number.
Richard Harter, cri@tiac.net, The Concord Research Institute
URL = http://www.tiac.net/users/cri, phone = 1-508-369-3911
Life is tough. The other day I was pulled over for doing trochee's
in an iambic pentameter zone and they revoked my poetic license.