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

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From: Ste on 15 Feb 2010 19:14

On 15 Feb, 19:37, PD <thedraperfam...(a)gmail.com> wrote:
> On Feb 15, 1:20 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > No, I'm saying that one should treat with utmost suspicion those who
> > say the essential concepts of some theory cannot be understood in
> > familiar everyday terms, and can only be understood within the terms
> > of its own special language.
>
> I'm not sure why. It's a matter of economy. For example, when speaking
> of rotation, you have in mind a *particular kind* of rotation -- a
> spatial rotation -- because that's what so in everyday terms. But this
> is a *special case* of what rotation means. Now, physicists have a
> choice here: 1) They can cow to the everyday language and instead of
> saying "rotation" they can say "generalized rotation which the
> following broader meaning: [etc]" and repeating that phrase every time
> they want to talk about rotation in general and not spatial rotations
> in specific, lest someone get confused and think that "rotation" means
> the same thing as the specific case; or 2) They can urge the reader to
> broaden their understanding of the term "rotation" so that spatial
> rotation thenceforth becomes recognized as the special case for the
> reader as well, and so that "rotation" can be used to mean the
> generalized term and "spatial" rotation" can mean the special case.
>
> There's a sound reason for preferring the latter, though it does pose
> a learning curve for the reader.

No I actually agree with you Paul. The use of the word "rotation" is
perfectly legitimate in this context, to describe a geometric
transformation. My argument is that those who claim knowledge here
don't seem to emphasise strongly enough, when queried, that this
geometric rotation into time bears *absolutely no resemblance at all*
to the physical act of spatial rotation.

> > I can understand "rotation" in geometric terms, and indeed I can
> > immediately see how rotation into time involves no different a
> > mathematical procedure than rotation in space. But in physical terms,
> > it seems to me the differences are vast.
>
> And the differences between whales and tetrapod land mammals are vast,
> even though in the abstract meaning of mammals, those differences
> become ancillary details.
>
> And this is precisely the point -- the MEANING of "mammal" as
> *properly* understood should make it apparent that the differences are
> ancillary details, rather than huge and fundamental differences. Or
> another way of looking it is that if someone thinks of mammals as
> tetrapod land animals, using the specific class to mean the same as
> the general term, and so that whales appear to be mammals "on paper
> only" but obviously not of the familiar class of tetrapod land
> mammals, then this person does not have a clear understanding of what
> the term "mammal" means.

I actually tend to avoid this sort of concrete classification - it
only leads to trouble if you place strain on it. But even so, whatever
physical characteristics mammals share in common, there is absolutely
no common physical basis between spatial rotation and this alleged
temporal rotation. Indeed time itself shares absolutely nothing
physically in common with the 3 spatial dimensions.

> > I'm not saying it meant either of those things. I'm just giving you an
> > example of how you would describe something in terms of everyday
> > language. Obviously, because you know the true nature of this
> > "rotation into time" and I don't, then it's for you to describe (if
> > you can and so wish to do so) the essential features in everyday terms.
>
> And that's the problem, you see. Everyday language attempts to
> pigeonhole things that do not belong in any of the available
> pigeonholes. This is the point that Feynman makes in "The Character of
> Physical Law". Our everyday language categorizes physical things that
> propagate into two disjoint categories: particles and waves. It is
> therefore natural to ask, in everyday terms, whether so-and-so is a
> particle or is a wave. Those are the only two available pigeonholes
> from everyday experience. The problem is, we've learned that a large
> group of physical things that propagate do not fall into either
> category and have to be described by a new category. Yet, in an appeal
> to everyday experience, this expansion opportunity is unavailable, as
> there are only those two classes available from everyday experience.

I'm not sure anyone has demanded that EM be either a particle or a
wave. Indeed, I'd be open to any reasonable physical concept. But it's
not good enough to say something is a particle and a wave, because
those two things are mutually exclusive in physical terms. If
something has both behaviours, then that's something that modern
physics needs to explain coherently.

> Yet, if we try to categorize any of these physical things as a
> particle, we make mistakes, and if we categorize them as waves, we
> make mistakes. There are things in nature, as Feynman says, that are
> simply not like anything we've ever seen before, and so our everyday
> categorizations and descriptions are simply insufficient.

I'm ambivalent about Feynman. There's some things that I'd agree with
him on, but this isn't one of them. I suspect there are some people
who think very concretely in verbal terms (or even mathematically),
and who need to learn to think a bit more vaguely and analogously, but
I tend to consider my own understanding to be fluid enough already and
my scepticism healthy, so I don't really need to be lectured about how
my preconceptions are a bar to my understanding. As I've said, I can
recognise that brilliant mathematicians are necessary for physics, but
they are certainly not sufficient.

From: Ste on 15 Feb 2010 19:32

On 15 Feb, 19:54, mpalenik <markpale...(a)gmail.com> wrote:
> On Feb 15, 1:40 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > > Velocity is rotation, just rotation in a way that you're not used to
> > > being able to rotate. There's nothing else to explain. You
> > > accellerate something, it rotates. That's a physical answer.
>
> > But you could give a simple demonstration of spatial rotation. Indeed,
> > people knew how to rotate things in space long before formal geometry
> > was ever developed.
>
> I can give you a simple example of the rotation I've just described.
> Accellerate an object. That's a rotation. The only reason people do
> not recognize it as such is because we can't step back and see the
> geometry of the 4 dimensional universe.

As I said, the real world existed long before geometry.

> However, to an observer who sits in a 3D cross section of spacetime,
> this is exactly how rotations would appear.
>
> It's like you're living in flat land, but flatland is sitting on a
> platform moving upward (representing your "motion" through time). A
> rotation out of the plane in flat land might not look exactly like a
> normal rotation that the flatlanders are used to, but mathematically,
> it would still be recognizable.

Mark, this is just meaningless. You're just thinking of a way to
describe the same *mathematical* concepts in concrete terms, which
actually detracts from the coherence and credibility of the
explanation.

> It's the same with SR. The fault is your perceptions, not the
> explanation.

No the fault is that you don't (or most probably can't) tailor your
explanation to the audience. I dare say the next time someone asks for
a "physical explanation", you'd do better to just say "I don't
understand relativity in those terms", and then everyone knows where
they stand. That's not at all to devalue the skills that you do have,
but it is to recognise that you either lack the capability or the
inclination to explain your understanding in terms that this
particular audience can understand, and you would do well to recognise
this as a deficit, rather than chalking it up to the "preconceptions"
of others.

> > But "rotation into time" is totally meaningless in the sense that it's
> > supposed to have any analogy with spatial rotation. It's a bit like
> > "light follows a groove in space" - the supposed concrete analogy
> > actually introduces more confusion.
>
> It's not just an analogy, it's a physical reality. Look at the
> picture I drew you. It means exactly what that picture shows (except
> in Minkowski spacetime, rather than euclidean).

It *represents* something in the real world. It is not physical
reality itself. At least, it isn't for people like me.

> The picture I made for you wasn't supposed to represent an analogy--it
> was supposed to represent physical reality (except with a slightly
> different metric--but we don't need to worry about that just yet).

If you don't recognise geometry as being an abstract *representation*
of the physical world, as opposed to the physical world itself, then
that is a clear difference in our understandings - and it's a
philosophical difference which will not be reconcilable.

From: PD on 15 Feb 2010 20:18

On Feb 15, 6:14 pm, Ste <ste_ro...(a)hotmail.com> wrote:
> On 15 Feb, 19:37, PD <thedraperfam...(a)gmail.com> wrote:
>
>
>
> > On Feb 15, 1:20 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> > > No, I'm saying that one should treat with utmost suspicion those who
> > > say the essential concepts of some theory cannot be understood in
> > > familiar everyday terms, and can only be understood within the terms
> > > of its own special language.
>
> > I'm not sure why. It's a matter of economy. For example, when speaking
> > of rotation, you have in mind a *particular kind* of rotation -- a
> > spatial rotation -- because that's what so in everyday terms. But this
> > is a *special case* of what rotation means. Now, physicists have a
> > choice here: 1) They can cow to the everyday language and instead of
> > saying "rotation" they can say "generalized rotation which the
> > following broader meaning: [etc]" and repeating that phrase every time
> > they want to talk about rotation in general and not spatial rotations
> > in specific, lest someone get confused and think that "rotation" means
> > the same thing as the specific case; or 2) They can urge the reader to
> > broaden their understanding of the term "rotation" so that spatial
> > rotation thenceforth becomes recognized as the special case for the
> > reader as well, and so that "rotation" can be used to mean the
> > generalized term and "spatial" rotation" can mean the special case.
>
> > There's a sound reason for preferring the latter, though it does pose
> > a learning curve for the reader.
>
> No I actually agree with you Paul. The use of the word "rotation" is
> perfectly legitimate in this context, to describe a geometric
> transformation. My argument is that those who claim knowledge here
> don't seem to emphasise strongly enough, when queried, that this
> geometric rotation into time bears *absolutely no resemblance at all*
> to the physical act of spatial rotation.

Well, that would be also going too far. The spatial rotation is a
special case of the general rotation, after all, so they can't be
*completely* different things.
To continue pounding on my analogy, it is incorrect to say that whales
bear *absolutely no resemblance at all* to tetrapod land mammals. They
bear a *strong* resemblance on the issues that pertain to being a
mammal.

But I understand your plea. You feel it is the burden of the expert to
be sure that the novice does not misconstrue, which includes actively
forestalling all places where they may make an erroneous assumption. I
can see why this might be expected as part of a teaching arrangement,
in a teaching venue, where the participants have clear teacher and
student roles. But in an informal discussion group, it's less clear
where the burden lies, you see.

>
>
>
> > > I can understand "rotation" in geometric terms, and indeed I can
> > > immediately see how rotation into time involves no different a
> > > mathematical procedure than rotation in space. But in physical terms,
> > > it seems to me the differences are vast.
>
> > And the differences between whales and tetrapod land mammals are vast,
> > even though in the abstract meaning of mammals, those differences
> > become ancillary details.
>
> > And this is precisely the point -- the MEANING of "mammal" as
> > *properly* understood should make it apparent that the differences are
> > ancillary details, rather than huge and fundamental differences. Or
> > another way of looking it is that if someone thinks of mammals as
> > tetrapod land animals, using the specific class to mean the same as
> > the general term, and so that whales appear to be mammals "on paper
> > only" but obviously not of the familiar class of tetrapod land
> > mammals, then this person does not have a clear understanding of what
> > the term "mammal" means.
>
> I actually tend to avoid this sort of concrete classification - it
> only leads to trouble if you place strain on it. But even so, whatever
> physical characteristics mammals share in common, there is absolutely
> no common physical basis between spatial rotation and this alleged
> temporal rotation.

I disagree. You just don't see it yet. That's ok. There are some
people who do not see any common connection between whales and camels,
either.

> Indeed time itself shares absolutely nothing
> physically in common with the 3 spatial dimensions.

And again, that's where you're mistaken. For example, it makes much
more sense to use the same physical units (either meters or seconds)
for BOTH space and time, and it is only by virtue of completely
capricious and foolish historical convention that it is not so. Taylor
and Wheeler wrote a superb Parable of the Surveyors to kick off their
book Spacetime Physics that makes this abundantly clear.

>
>
>
> > > I'm not saying it meant either of those things. I'm just giving you an
> > > example of how you would describe something in terms of everyday
> > > language. Obviously, because you know the true nature of this
> > > "rotation into time" and I don't, then it's for you to describe (if
> > > you can and so wish to do so) the essential features in everyday terms.
>
> > And that's the problem, you see. Everyday language attempts to
> > pigeonhole things that do not belong in any of the available
> > pigeonholes. This is the point that Feynman makes in "The Character of
> > Physical Law". Our everyday language categorizes physical things that
> > propagate into two disjoint categories: particles and waves. It is
> > therefore natural to ask, in everyday terms, whether so-and-so is a
> > particle or is a wave. Those are the only two available pigeonholes
> > from everyday experience. The problem is, we've learned that a large
> > group of physical things that propagate do not fall into either
> > category and have to be described by a new category. Yet, in an appeal
> > to everyday experience, this expansion opportunity is unavailable, as
> > there are only those two classes available from everyday experience.
>
> I'm not sure anyone has demanded that EM be either a particle or a
> wave.

It might be good to look up the historical development of the notion
of the quantum, then, as well as the philosophical wrangling over
"particle-wave duality".

> Indeed, I'd be open to any reasonable physical concept. But it's
> not good enough to say something is a particle and a wave, because
> those two things are mutually exclusive in physical terms.

And that's not exactly what's said. What's said is that it is NEITHER
a particle or a wave, but exhibits some properties of particles and
some properties of waves.

> If
> something has both behaviours, then that's something that modern
> physics needs to explain coherently.

Why? It's a class of objects that is discovered in nature and the
behaviors are *observed*. Why do we have to explain WHY our
pigeonholing doesn't work for them, other than to acknowledge there is
something wrong with our pigeonholing scheme?

After all, viruses do not meet the usual criteria of "living things",
nor do they meet the usual criteria of "nonliving things". They have
*some* of the properties of both. Does this mean that we have to
explain why viruses can exist, because they resist our pigeonholing?

>
> > Yet, if we try to categorize any of these physical things as a
> > particle, we make mistakes, and if we categorize them as waves, we
> > make mistakes. There are things in nature, as Feynman says, that are
> > simply not like anything we've ever seen before, and so our everyday
> > categorizations and descriptions are simply insufficient.
>
> I'm ambivalent about Feynman. There's some things that I'd agree with
> him on, but this isn't one of them. I suspect there are some people
> who think very concretely in verbal terms (or even mathematically),
> and who need to learn to think a bit more vaguely and analogously, but
> I tend to consider my own understanding to be fluid enough already and
> my scepticism healthy, so I don't really need to be lectured about how
> my preconceptions are a bar to my understanding. As I've said, I can
> recognise that brilliant mathematicians are necessary for physics, but
> they are certainly not sufficient.

From: PD on 15 Feb 2010 20:27

On Feb 15, 6:56 pm, Ste <ste_ro...(a)hotmail.com> wrote:
> On 16 Feb, 00:26, "Inertial" <relativ...(a)rest.com> wrote:

>
> > Physics does not say that. It does say that EM (and other quantum objects)
> > exhibit both wave-like and particle-like behavior. That doesn't mean it
> > *is* both a particle AND a wave.
>
> Indeed, but physics doesn't seem to be saying what it *is*.

Well, indeed, you really don't have much more of an idea what a wave
*is*, or a particle *is*, though you can probably think of examples.
And in fact, these categories are defined by collections of behaviors.
We say something is a wave because of the way it behaves.
Likewise, we describe this new class of things, called "quantum
fields", by the way they behave.

>
> It does not need to be "something I've seen before". It needs only be
> something physical and concrete, instead of waffling about things like
> "collapse of the wavefunction". And indeed, I'm a strong believer that
> the essential and meaningful features of the world don't change a
> great deal over time.

This would be a mistake. Indeed, what we did in the last 100 years or
so is instrument ourselves to be sensitive to a huge range of the
universe that had been previously out of our sensory experience. Our
language and conceptual frameworks were all based on the small slice
that had represented our view of reality before that. Suddenly there
was a very rapid explosion of new behaviors and classes of physical
objects that were previously unknown to us, but our language and
mental imagery has not really caught up -- especially those two things
as they are commonly understood by what you call "ordinary people".

From: kenseto on 15 Feb 2010 21:59

On Feb 15, 5:16 pm, "Inertial" <relativ...(a)rest.com> wrote:
> "kenseto" <kens...(a)erinet.com> wrote in message
>
> news:65b0b432-ea12-4f62-8dea-14b916d28a20(a)15g2000yqi.googlegroups.com...
>
>
>
>
>
> > On Feb 15, 4:06 pm, PD <thedraperfam...(a)gmail.com> wrote:
> >> On Feb 15, 2:38 pm, kenseto <kens...(a)erinet.com> wrote:
>
> >> > On Feb 15, 12:27 pm, mpalenik <markpale...(a)gmail.com> wrote:
>
> >> > > On Feb 15, 6:54 am, Ste <ste_ro...(a)hotmail.com> wrote:
>
> >> > > > On 14 Feb, 23:46, mpalenik <markpale...(a)gmail.com> wrote:
>
> >> > > > > On Feb 14, 2:03 pm, Ste <ste_ro...(a)hotmail.com> wrote:
>
> >> > > > > > I'm afraid you're easily satisifed Tom. As I say, I'm not
> >> > > > > > really
> >> > > > > > interested in learning geometry, or talking about completely
> >> > > > > > hypothetical "grooves in spacetime".
>
> >> > > > > And as many people have repeatedly tried to explain to you, the
> >> > > > > answer
> >> > > > > simply is geometry. When you accellerate, you rotate in
> >> > > > > spacetime.
> >> > > > > Why? Because that's what accelleration means. That's what it
> >> > > > > means
> >> > > > > to be travelling with a certain velocity with respect to
> >> > > > > something
> >> > > > > else. It means that you're both "facing different directions".
> >> > > > > Every
> >> > > > > effect predicted by relativity can be explained simply by the
> >> > > > > fact
> >> > > > > that two different observers at different speeds are "facing
> >> > > > > different
> >> > > > > directions" in spacetime--because that's what it means to be
> >> > > > > moving
> >> > > > > with respect to something else. It means that you have a
> >> > > > > different t
> >> > > > > and x axis.
>
> >> > > > Mark, if you consider this an answer, then you simply haven't
> >> > > > understood the question.- Hide quoted text -
>
> >> > > > - Show quoted text -
>
> >> > > And if you think there's more to it than that, then you haven't
> >> > > understood the answer. The above explains everything about
> >> > > relativity
> >> > > and there's no ambiguity when you understand it.
>
> >> > > Going back to the fitting a ladder into a barn analogy, it's like you
> >> > > have a ladder to long to fit into the barn, you turn it at an angle,
> >> > > and it fits, and then someone starts asking you what "physically"
> >> > > happened to the ladder. You say "well, it got rotated, so it's
> >> > > shorter in the horizontal direction". Then the person keeps
> >> > > demanding
> >> > > a physical explanation, and you say you just rotated the ladder, so
> >> > > it
> >> > > takes up a bit more space in the vertical and less in the horizontal
> >> > > but the total length of the ladder didn't change.
>
> >> > In this case you are not fitting the length of the ladder through a
> >> > narrow door way. You are fitting a skinny side of the ladder through a
> >> > wider door way.
> >> > This is not the same as an 80 ft long material pole can fit into a 40
> >> > ft long material barn with both doors close simultaneously. In this
> >> > case material contraction must occur. That's thee reason why modern
> >> > interpretation of length contraction in Sr is merely a geometric
> >> > effect instead of material or physical effect as asserted by the
> >> > runts of the SRians such as PD and you.
>
> >> "Material" does not mean the same thing as "physical", Ken.
> >> This has been pointed out even in the common dictionary.
> >> If you can't let go of your mistakes, Ken, you'll never get off square
> >> one.
>
> > Physical is material....is one of the definitions in my dictionary.
>
> My dictionary says it is relating to the human body (as opposed to mind or
> spirit), or involving bodily contact. So if you mean length contraction in
> SR is not physical because it does not involve human body contact, then I'd
> agree.
>
> In any case, SR says the all the atoms of a moving rod are closer together
> (in the frame of a relatively moving observer). ie. that the spatial
> distance between them (at any given time) is shorter than when the rod is at
> rest. That sounds 'physically' shorter to me.

Hey idiot do you realize that you were describing material length
contraction and not merely geometric projection contraction? If
material length contraction occur how come from the pole frame point
of view there is no material length contraction and thus it is not
able to fit into the barn? Do you realize that material length
contraction is frame independent?

Ken Seto

>
> But then .. you think that geometric things like rotation and translation
> are not physical .. so by your logic, when an object gets compressed, it is
> really just a geometric effect of the atoms translating closer together, but
> not a material change to the atoms themselves, so therefore it is not
> physical.
>
> You do realize that geometry is just a human model for what is happening
> 'physically' in reality (depending on which geometry you use .. you can have
> geometries that are not models of any reality we are aware).- Hide quoted text -
>
> - Show quoted text -