A constant speed of light in all reference frames? Surely you can't be serious. [Physics]

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From: Ste on 28 Feb 2010 00:23

On 27 Feb, 15:46, PD <thedraperfam...(a)gmail.com> wrote:
> On Feb 26, 6:46 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
>
>
>
>
> > On 26 Feb, 12:52, "Inertial" <relativ...(a)rest.com> wrote:
>
> > > "Ste" <ste_ro...(a)hotmail.com> wrote in message
>
> > > > Of course I'm not claiming to know anything profound about the solar
> > > > system. The conceptual model has been accepted for centuries, and I'm
> > > > not pretending to add anything new to it. The point I was making about
> > > > it is that the conceptual model is required to give any real meaning
> > > > to the equations.
>
> > > We already have such model .. that's the whole POINT of physics .. it is
> > > modeling reality. How reality behaves is the meaning to the equations ..
> > > they describe what is going on.
>
> > Then show the equations to a child. Ask him if he understands what is
> > going on. And remember, you're not allowed to mention the conceptual
> > aspect, or appeal to sensory perception. You must only use the
> > equations. If these equations alone describe what is going on
> > meaningfully, then the child ought to understand immediately.
>
> I'm not sure I buy the argument that anything should be fundamentally
> understandable to a child.

The point was to explain the theory to someone who hasn't already
implicitly internalised the conceptual model on which the equations
rest. This is, after all, the test of whether the equations are a
complete description of reality, as Paul contends.

You could substitute uneducated adults, or even foreign cultures, for
the child, but that would probably attract the criticism that the
problem is one of language, inherent (lack of) ability, or cultural
incompatibility to account for the failure of those others to
comprehend the meaning of the equations. Whereas, if we start with a
child, we at least assume that they speak the same language, have a
similar level of exposure to our culture (but are not yet educated in
science), and have a reasonable amount of ability.

From: Peter Webb on 28 Feb 2010 01:25

"Ste" <ste_rose0(a)hotmail.com> wrote in message
news:00434686-8fca-4ca5-a321-8f68700d1e41(a)o3g2000yqb.googlegroups.com...
> On 27 Feb, 12:53, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
> wrote:
>> "Ste" <ste_ro...(a)hotmail.com> wrote in message
>>
>> news:f47fb4af-7f73-420b-b61b-73a4ce42b1e5(a)q15g2000yqj.googlegroups.com...
>>
>>
>>
>>
>>
>> > On 27 Feb, 06:55, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au>
>> > wrote:
>> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message
>>
>> >>news:2268f44a-518e-43b4-a3f8-a610f4e89e89(a)o30g2000yqb.googlegroups.com...
>>
>> >> > On 26 Feb, 12:31, "Peter Webb"
>> >> > <webbfam...(a)DIESPAMDIEoptusnet.com.au>
>> >> > wrote:
>> >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message
>>
>> >> >> About this gravity thing. I am having a great deal of difficulty
>> >> >> forming
>> >> >> a
>> >> >> mental picture of how it is supposed to work.
>>
>> >> > At a fundamental level, I do too.
>>
>> >> >> If the planets are separated
>> >> >> by vacuum, how could one object possibly pull on another object
>> >> >> when
>> >> >> there
>> >> >> is nothing between them? For that matter, how does one particle
>> >> >> manage
>> >> >> to
>> >> >> pull on every other particle in the Universe at the same time? Are
>> >> >> you
>> >> >> positing some array of invisible springs, 10^160 of them,
>> >> >> connecting
>> >> >> the
>> >> >> 10^80 particles in the Universe?
>>
>> >> > I think a more credible argument is that there *is* in fact
>> >> > something
>> >> > in between the objects.
>>
>> >> >> Frankly, I find the suggestion that each time I move my finger to
>> >> >> type
>> >> >> these
>> >> >> invisible gravity springs cause every other particle in the
>> >> >> Universe
>> >> >> to
>> >> >> move
>> >> >> ludicrous. Apart from anything else, how is this spooky action at a
>> >> >> distance
>> >> >> supposed to work, physically? Springs and levers? What is gravity
>> >> >> supposed
>> >> >> to be, physically?
>>
>> >> > I don't find it hard to believe that every movement of the finger
>> >> > could have an effect on every other particle of the universe. In
>> >> > terms
>> >> > of what gravity is and how it works, that remains to be explained.
>>
>> >> Ohhh, so your mental model of the solar system contains "gravity", yet
>> >> your
>> >> mental model of the solar system provides no physical explanation of
>> >> what
>> >> it
>> >> "really" is.
>>
>> >> Funny, you complained about SR and Minkowski for having components for
>> >> which
>> >> you have no physical model. Yet your own theory of the solar system
>> >> contains
>> >> concepts such as gravity which have no physical explanation at all
>> >> within
>> >> the model.
>>
>> > Yes, but I readily concede this, and accept that there needs to be
>> > work done to find out what gravity actually is. For the time being, I
>> > have a model that operates at a macro level, where gravity is assumed
>> > to be a fundamental manifestation of reality. Yet you speak as though
>> > I've let the cat out of the bag or something.
>>
>> So you have no *physical* idea of what gravity really is, but that
>> doesn't
>> stop you using it in a model.
>>
>> Funny, the fact that SR contains things which you have no *physical*
>> explanation of was a huge problem for SR, but the same problem doesn't
>> worry
>> you for your own model.
>
> How on Earth have you drawn that conclusion? On the contrary, I hold
> that it *is* a problem that there is no apparent physical explanation
> for gravity (in terms of what it is, how it is mediated, how it
> relates to other forces, etc).

I am demonstrating that you are inconsistent in your requirement that
explanations be physical.

You claimed that you had a physical model "in your head" of how the solar
system rotates - involving orbits, masses and "gravity". But your model has
no physical explanation for gravity. It is no more a physical description of
the solar system than Minkowski is of SR - both models contain things which
have no physical explanation (according to you, anyway). Yet you accept
these in your model of the solar system (as did Newton in his model), but
reject them for SR.

You may well have an intuition as to what gravity is, but no intuition as to
what SR predicts. That's only because you live inside a gravity well, but
planes don't fly at 0.9 c. Reverse these and you would have an excellent
intuition as to SR, but none as to gravity. Your intuition is a comment only
on your personal experience, and not on what happens when objects are
accelerated to near the speed of light.

The great and interesting thing about science and maths is how often
intuition is completely wrong. These are the experiments which really test a
theory. If intuition was always right, we wouldn't need science, we would
just use our intuition when we decide how big the magnets have to be in a
particle accelerator, and not bother discovering SR at all.

From: Ste on 28 Feb 2010 01:54

On 27 Feb, 15:54, PD <thedraperfam...(a)gmail.com> wrote:
> On Feb 26, 6:54 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > On 26 Feb, 17:34, PD <thedraperfam...(a)gmail.com> wrote:
>
> > > On Feb 25, 9:05 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > > > I also doubt one exists at the moment, but I see that as a problem.
> > > > It's utterly irreconcilable, within any conceptual framework that I
> > > > know of, to have situations where, for example, a large ladder can end
> > > > up in a smaller barn according to an observer stationary in the barn,
> > > > but not according to an observer riding the ladder.
>
> > > Why? And here we can systematically trace back to the assumptions you
> > > are making and then question them. In this case, you have a firm
> > > belief that length is definable in such a way that it is intrinsic to
> > > the object and frame-independent, and that physical "fitting" is a
> > > function of the *intrinsic* lengths of two objects (or an object and a
> > > container).
>
> > My only contention is that it is *not realistic* to say that from the
> > barn frame frame the ladder contracts and fits inside, while saying
> > that from the ladder frame it is the barn that contracts and the doors
> > actually never shut simultaneously. It is simply not realistic.
>
> I don't know what basis you have for judging whether something is
> "realistic".

I must admit I can't quite put my finger on it myself.

> I'm guessing that it means that it is consistent with
> your intuition, and that your intuition tells you that something
> cannot fit in one frame and not fit in another, or that two events are
> simultaneous in one frame and not simultaneous in another. If this is
> accurate, then I would ask on what basis you trust your intuition. Or,
> even more aptly, why do you trust your intuition so much that you rule
> out other possibilities as real if they conflict with your intuition?

Because on the one hand my physical (i.e. practical-mechanical)
intuitions are well-developed and highly consistent with my experience
of reality, and secondly it is not readily apparent that SR is
inconsistent with these intuitions. In the face of people who suggest
the two are inconsistent, obviously I've got to first consider whether
there's a language difference between me and the opponent (i.e. no
common apprehension of verbal meaning), and secondly whether the
opponent is confused or simply wrong (i.e. no common apprehension of
the evidence).

The ultimate resolution of this question seems to be confounded
firstly by the degree to which there is no shared language, secondly
the degree to which opponents seem to be unclear about the conceptual/
qualitative basis of SR, and thirdly the preconceptions and
psychological style of many posters.

> > If
> > such a thing appears to happen, then it is obviously an artefact of
> > subjective observation.
>
> I disagree. In science, if there is a conflict between experimental
> observation and intuition, then it is *intuition* that becomes
> suspect, not the experimental result, especially if the latter is
> confirmed independently and by complementary means.

I'm afraid there is no room for a discrepancy between intuition and
observation. Intuition is supposed to account for observation, and
there is no question of observation taking a back seat to intuition.
So that in that way we agree.

But this is not the same as crude observationalism.

> > > > > Your disbelief of SR stems from the fact that you don't understand it.
>
> > > > My disbelief, really, stems from the blatant lack of conceptual
> > > > understanding of the theory. I mean, as I repeatedly point out, I
> > > > don't know a single equation of relativity, and yet I can root out the
> > > > conceptual contradictions immediately when people here have a crack at
> > > > making meaningful qualitative statements in SR. The classic example,
> > > > of course, was Paul's contention that "what is simultaneous in one
> > > > frame can never be simultaneous in another", which of course isn't
> > > > true according to SR.
>
> > > I'm sorry? It is very much true in SR that two spatially separated
> > > events that are simultaneous in one frame are not simultaneous in
> > > another frame moving relative to the first.
>
> > But I contradicted that when I pointed out that two observers can be
> > moving relative to each other, and yet undoubtedly events can be
> > simultaneous for both.
>
> Not spatially separated ones, no.

I'm confused, because I thought we previously agreed that two
observers travelling along the same axis, maintaining equidistance
from both events at all times, would both report each event as
simultaneous with the other event. And moreover, if they not only both
maintained equidistance from both events, but if they maintained a
separation which was equal for both observers (which, if both
observers are moving relative to each other, requires either a
collision course between observers, or travel in diametrically
opposite directions), then there is no question that the signals are
received simultaneously.

Illustration:

E1

--------

E2

The line represents the line between events E1 and E2, along which the
observers may move while always reporting both events to be
simultaneous.

From: Ste on 28 Feb 2010 02:05

On 27 Feb, 15:58, PD <thedraperfam...(a)gmail.com> wrote:
> On Feb 26, 6:59 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > > There's a variety of things one can do (and are done).
> > > 1) Explore other candidates, though at a level that is commensurate
> > > with risk-benefit analysis of the effort involved.
> > > 2) Continue to do other tests of this model vs other models to see
> > > where the 5% might lead (to either opening it up to 40% or closing it
> > > to 98%, say)
> > > 3) Let the community by itself determine organically which volunteers
> > > from the community will plumb the 5% doubt.
> > > 4) Design a bunch of devices that are based on a 95% assurance that
> > > the principles of that model are correct, again weighing risk vs
> > > benefit on the chance this is a mistake.
>
> > That's fair enough in abstract. But the question is still who pursues
> > which avenue, and what subjective perception they have of the
> > likelihood of a particular theory being correct.
>
> Yes, and that is done by self-selection. In the community of
> scientists, the presumption is that open questions will be addressed
> by someone eventually. And there is reward in the community for that
> adventurism. The assessment of the risk vs benefit of the adventurism
> is made individually.

Indeed. But it is then a sociological question, to ask which
scientific questions are answered and which are not, and why.

From: Peter Webb on 28 Feb 2010 02:07

"Ste" <ste_rose0(a)hotmail.com> wrote in message
news:859fe48e-4473-4e46-ab5d-16cf91687eac(a)z11g2000yqz.googlegroups.com...
On 27 Feb, 15:44, PD <thedraperfam...(a)gmail.com> wrote:
> On Feb 26, 6:34 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > > > The fact that this conceptual model in a raw form
> > > > can permit predictions that are so permissive as to make almost no
> > > > prediction at all, does not mean they are not an essential component
> > > > to scientific enquiry and advance.
>
> > > No testable predictions = not science. Possibly philosophy, possibly
> > > fiction, possibly drug induced free association speech, possibly
> > > gibberish,
> > > possibly an incredibly profound insight into human emotions, possibly
> > > masturbation. But not science. Science makes testable predictions.
> > > (Note
> > > that this is a necessary but not sufficient condition. Astrology also
> > > makes
> > > predictions, just very poorly).
>
> > I think you're attributing an absurd definition to "science". Paul
> > Draper probably had a more tenable argument when he said that string
> > theorists are scientists doing science, but that they do not yet have
> > a "scientific theory". But I know from talking to him that he
> > attributes a very contorted meaning to the phrase "scientific theory",
> > that would condemn a lot of scientific knowledge, both historical and
> > current, as being "unscientific".
>
> Examples, please.

In physics I would raise the same old example: string theory . But
there are certainly more. We have things like "dark matter". Or even
Newton. Or Galileo. And more broadly, in biology we have evolution,
and in economics, rational choice theory.

__________________________________
All of these things are falsifiable, or they are not scientific theories. I
don't know much about string theory, but the rest are certainly falsifiable.
Newton's theory was in fact falsified by observation. In another part of the
thread, I gave you half a dozen ways evolution could have been falsified.

All managed to fail your previously stated requirement of a
"scientific theory", which (amongst other things) is being falsifiable
(in a practical rather than just notional sense), not ad-hoc, and
predicting observations that are not already accounted for.

_______________________________
I didn't state any of these requirements other than it was falsifiable. All
of those theories are, at least as I understand them, with the proviso I
know zero about string theory and not a lot about some of the others. I have
already demonstrated how many of them in fact could be falsified.