Does Special Relativity contain contradictions?

[Steve3007]

I think this proves my point, the argument effectively being I can't conceptualise what the maths shows so the maths must be wrong, rather than 'the maths all adds up but my brain can't understand this'.

If that's what you think, then I think you'd probably like the philosophical point that was exemplified by the phrase (familiar in discussions of quantum physics) "shut up and calculate!". Apparently it was coined by the physicists David Mermin. But I've also heard it attributed to the physicist Richard Feynman, presumably because it sounds like the kind of pithy soundbite that Feynman might use.

Basically, it means that a lot of the observations of the world made in physics (being far removed from the sets of direct human experiences that collectively form our notions of common sense) do not appear to conform to common sense. It suggests that common sense (because of the way it is formed) is not a good guide. All we can do is concentrate on the observations themselves and the logical connections, expressed in the language of mathematics, that link those observations.

[Burning ghost]

Steve -

I would say that the root philosophical problem, as discussed with Greta above, of which all the specific talk about physics is a symptom, is the question of what exactly physics (and science in general) does and doesn't do, and aspire to do. I propose that physics discovers invarients in the different measurements of individual observers. It calls those invariants laws. This is related to the question of whether the laws of physics are deemed to be created or discovered.

Easy enough to address what science does. We have a world of phenomenon by which we ascribe model to understand said world based on set assumptions and methods of measurement. Our capacity to measure precisely is inhibited by our cognitive capacities.

We “discover” models that work and refine them over time as and when better or new evidence comes to hand.

It is essentially a method in which subjectvity is held at bay as best as possible in order to establish a set of standards that can be satified by everyone through experimentation. The major difficulty of science is to simply look at the data gathered and to try and decipher what we can from it whilst holding our opinions and theories at bay - and contrary to this to have a “new idea” we must create some means of experimentation and testing in order to satify the community.

You and everyone here pretty much knows this right. The issue of “discover” or “create” is vague if we wish to be pedantic about the “objectivity” of science.

Newtonian mechanics weren’t “wrong” and SR isn’t “wrong” either. They are just models that propose an accurate enough explanation to what we can measure on different scales. We certainly don’t have a GUT of any kind. I’m no mathematician or physicist - my knowledge is quite, quite shallow in that area. I know enough to know the abstract use of the methodology is very counter intuitive for mere day-to-day human living.

[Thinking critical]

The argument is that an observer who makes measurements against one reference frame is asserting things that contradict the assertions of an observer who makes measurements against another reference frame which is moving relative to the first one. The argument (as I understand it) proposes that there is only one possible reference frame that allows an observer to "accurately represent reality" and that this reference frame is stationary relative to the aether. The aether is/was the proposed medium through which light and other electromagnetic waves propagate.

The fundamental point which seemed to elude David, was the fact that relativity essentially serves a useful purpose specific to the observer (us) to describe the behaviour of objects. The point to remember is relative...... David was imagining himself making measurements from two different locations (frames) at once then complaining because that data was inconsistent. First of all, if thought experiments create paradoxes they cannot occur in reality, so in other words we can never simutianeously exist in two time frames meaning there is no paradox.
Secondly, if speed is measured relative to a universal constant (C) the method becomes empirical, not logical, so again no paradoxes.

[Steve3007]

The fundamental point which seemed to elude David, was the fact that relativity essentially serves a useful purpose specific to the observer (us) to describe the behaviour of objects. The point to remember is relative......

The way I'd put it is that the Principle of Relativity, of which Special Relativity is an extension, does what laws and principles of physics are supposed to do. It shows us the things which are invariant (which do not change) for all observers.

David was imagining himself making measurements from two different locations (frames) at once then complaining because that data was inconsistent.

I think it's important to be clear in our use of terminology to avoid unnecessary confusion. A reference frame is a set of coordinates against which the position of any object, at any location, can be measured. Two different reference frames could (momentarily) have their origins at the same location relative to various objects but still be different reference frames if one of them is moving with respect to the other. I think David complains of inconsistency because he insists on saying that reference frames assert things, rather than saying that observers make measurements against reference frames.

[Halc]

The original thread is winding down, and David's sole reply to me contains almost nothing to which I have not already responded. I'll pick out only a couple new things, and post them only here. Unclear if David intends to respond here.

Naturally enough though, SR folk like to claim that SR fits the experiments too, which means they may twist things in places to make it fit them or just ignore the parts that don't fit, and that's why they don't get a tick in every box. Perhaps you could point to some invalid physics on his site (other than the invalid physics that he's attacking).
...
It is a high-quality site with high-quality information. Show me where it's broken.

OK, from the page showing how SR needs to be 'twisted' to predict the Sagnac effect: http://www.conspiracyoflight.com/Sagnac ... ndRel.html

On the other hand, the observer at A who is rotating with the disk has observed that the source and detector are stationary from his perspective, as are the paths, so he can only conclude (assuming no foreknowledge that he is rotating) that the light has actually travelled at two different velocities around the disk, being C+v and C-v. Who is right? Well, the problem is this – from the point of view of special relativity, there are no preferred frames of reference, there are only relative frames of reference, so we can’t argue that frame B is better than frame A without defeating the underlying premise of the theory.

The guy rotating with the disk very much knows he is rotating, even without foreknowledge. The spinning bucket bit above event points this out, but the author conveniently forgets this here. SR makes no claims about light speed (or any of Newton's laws of motion for that matter) in a rotating reference frame. All stars (except our own) move much faster than light in the frame of the surface of the Earth. Stationary objects tend to begin to move without force being applied. Moving things do so in curved lines. f=mA doesn't work.
The last sentence in that quote is blatantly invalid physics. It is an embarassment to the author to twist things like that.
It seems to be the same strawman techniques that you have been pushing, even if you've not asserted that particular error. Case in point where you insist on a flowing time model when considering a model without it:

and by all three other modes if you imagine them building the block as they go.

That is not Minkowski spacetime.

Absolutely identical geometry.

But absolutely different metaphysics.

[Halc]

In a recent post in the dying embers of the old topic from which this new topic sprang, David Cooper has indicated to me that he disagrees with my description of the laws of physics as:

"Generalisations which we have created as a result of various measurements and observations."

He prefers this:

"Laws of physics are actualities of nature. Proposed laws of physics are attempts to reproduce them within theories."

This suggests to me that he thinks (to use Leo's phrase) that my definition mistakes the map for the territory.

I had responded to this that the former was physics, and the latter was metaphysics. Physics is the map, yes, but SR is about the map, not about the territory.

[Mark1955]

I'd say the only problem with the Lorentz aether hypothesis is that the experiments always fail to find the ether,

I think David Cooper's answer to this would be to say that the aether is not so very different from the concept of a "fabric of spacetime".

I'd have to disagree because the concept of Lorentz aether seems to me to be that it is invariant precisely so he can measure everything else against it; while space time is by definition relative depending on how [or where from] you measure things.[/quote]

I think he would say that concepts should not be abandoned just because they do not directly correspond to a possible empirical observation. I think he would say that some concepts exist in order to "make sense" of things.

Sadly for DC, from a scientific perspective we have to have empirical evidence. Anyone can come up with any concept [hypothesis] they like. Then we test it against the data, when it repeatedly fails to fit the data we discard it. The idea of 'making sense' is just another set of words for, 'fits my preconceived ideals' and is fine in religious philosophy but has no place in scientific philosophy.

[David Cooper]

I have only just found out about the existence of this thread, which is a pity, because it would have made sense to give me the opportunity to set out my position in the second post rather than on the second page.

What I have done is separate out all the different incompatible models that pass for SR and then disprove each in turn by showing the point where it breaks. There is no SR model that can survive this process. SR only carries on as a mixture of incompatible models which is asserted to be viable by slapdash people who fail to compartmentalise and analyse the models correctly. GR might just about come through as potentially viable in one form, but it's a far-fetched model which really shouldn't be given the time of day.

I'll say more when I have more time, but I'll just deal with Mark's posts now as they're highly significant:-

I'd say the only problem with the Lorentz ether hypothesis is that the experiments always fail to find the ether, which in it's way is a pretty big contradiction and why it shouldn't really be described as a theory.

The results of the experiments conform to the predictions of LET (Lorentz Ether Theory). No experiment has ever been devised that should be able to detect the aether.

Sadly for DC, from a scientific perspective we have to have empirical evidence. Anyone can come up with any concept [hypothesis] they like. Then we test it against the data, when it repeatedly fails to fit the data we discard it. The idea of 'making sense' is just another set of words for, 'fits my preconceived ideals' and is fine in religious philosophy but has no place in scientific philosophy.

Here we have a prime example of the degree to which the public has been misinformed by the establishment. LET has not failed any experimental tests, and, unlike SR, it's a rational theory. (Note that LET has also been extended to cover the same ground as GR, though this work was not done by Lorentz.)

[Steve3007]

I had responded to this that the former was physics, and the latter was metaphysics. Physics is the map, yes, but SR is about the map, not about the territory.

Yes, I would agree that physics is the map. The disagreements, in the case of both Obvious Leo and David Cooper, seem to emerge when discussing the relationship between map and territory. But they come to very different conclusions from each other. David has decided that he prefers the pre-existing Lorentz Ether Theory. Obvious Leo struck out on his own and proposed his own new theory based around the central role of time (as opposed to space, or space-time) and treating it as a fractal dimension. But I can't remember much more about it, apart from what Greta quoted earlier. Leo did propose an empirical test for his theory though, as I recall.

[Burning ghost]

I believe this could be a philosophical problem after all then!

The “map” and the “territory.”

There is, at the heart of it, no essential difference. All kinds of wacky theories are thrown around in this area. The issue with most of them is they are not “theories” only called such. The “map” in this case is the testable and reproducable experimentation that leads people to agree. The rest is merely hypothesis or just plain old creative spectulation.

The “territoty” is the data/information/experience available.

[Steve3007]

The “territoty” is the data/information/experience available.

This isn't my metaphor. It was (as far as I know) coined by the poster called Obvious Leo, who hasn't posted here for a long time. It's my understanding that, within this metaphor, "territory" refers to an objective reality which is proposed to be the cause of the experiences that you mention.

[Burning ghost]

Leo died a year or two ago.

In physics the issue of where the map ends and the territory begins is pretty much where philosophy tries to slot in and do something useful.

[Steve3007]

Leo literally died? When Greta said "the ghost of Leo" I didn't think it was meant literally. That is sad news. He was an interesting guy.

[Steve3007]

I think it simply comes down to this concept that David has of "reference frames which misrepresent reality". I think (correct me if I'm wrong) we all agree that in an inertial reference frame the ring is moving relative to that frame, and the light as measured against that reference frame, using a clock and two detectors that are close together, all three of which are stationary WRT that reference frame, will be observed to have speed c. And I think (correct me if I'm wrong) we all agree that an observer riding along the ring, with a clock and a pair of light detectors riding with him and close together, would also measure the speed of light as c. Where David seems to differ is in thinking that one or both of those measurements is, in some sense, "misrepresenting reality". And since he thinks that SR says that reference frames assert things that are asserted to be true for all reference frames (rather than simply being used to make measurements that can be used to devise laws of physics) this is why he claims that SR contains contradictions.

It's very simple. Frame A claims the speed of light relative to objects at rest in frame A is c in all directions. Frame B claims the speed of light relative to objects at rest in frame B is c in all directions. At least one of those claims must be wrong.

If frame A is an inertial reference frame then an observer who is stationary WRT that frame who measures the speed of light by referring to that frame will measure it as c. If frame B is another inertial reference frame then an observer who is stationary WRT that frame will also measure the speed of light with reference to that frame as c. Accurate measurements. Nobody asserts anything. No contradictions.

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The first postulate [that the laws of physics are the same for all inertial observers] is not ambiguous if you understand what laws of physics are. Laws of physics are generalisations created from observing the patterns in measurements which predict future measurements. The first postulate simply predicts that those measurements, and therefore the laws of physics that derive from them, will be found to be the same when measured against any non-accelerating reference frame.

But most people take it to mean that because the speed of light is represented as c relative to any frames, that is the actual physics too.

The first postulate does not mention the speed of light. Remember: take things one step at a time. The first postulate, as I keep on saying, is simply a generalisation of the Galilean Principle of Relativity.

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The more important issue is the absolute frame, and that is necessary to avoid contradictions, unless you're very specific about which model you're using...

Forget all the supposedly different models for now. Make sure you know the pre-SR basics. If we don't agree about those, and we don't agree what words mean, and we don't agree as to what a law of physics is, there's no point trying to discuss the finer points of a specific example of one of those laws of physics.

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If one frame says something is stationary and another says it's moving, it is clearly impossible to tell whether something is moving or not, so your objection to that one is frankly ridiculous.

Which is perhaps one reason why frames don't say that. Movement is defined as the change in the spatial distance between two objects with respect to time. So, if you use the correct definition of the word "moving", clearly we can work out if we're moving.

Frames do say that. You can measure movement in any way you like, but if something is not moving in one frame (no change in spatial distance between itself and any other object at rest in that frame) and is moving in another (with a change in spatial distance between other objects which are at rest in that frame), then we have contradictory claims from different frames about whether the object is moving or not, and we can't tell which one is wrong.

No we don't. We have an object that is moving with respect to one frame and not moving with respect to another. Your characterisation of this as "contradictory claims" seems truly mad. If I am driving a car and I find myself to be not moving with respect to the car but moving with respect to the Earth, I am not "making contradictory claims"! Yet that is what you're saying here.

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If, for the sake of brevity, you don't make that clear in your explanation it wouldn't be so bad if it wasn't for the fact that you build on that omission rather than explaining it.

The fact of it is that you can't tell if you're moving or not in an absolute sense unless you have an absolute frame...

If you postulate the existence of an aether and if you further postulate that it's impossible to measure the velocity of that aether with respect to any other object, then you can't tell if you're moving with respect to that aether. If that's what you mean by the above, then maybe there's at least something that we agree on. But I'm not holding my breath.

...That doesn't mean that there isn't an absolute answer known only to that absolute frame...

It sounds like you're talking about a God-like concept again. The absolute frame moves in mysterious ways that it is not for us to know.

...SR ordinarily denies the existence of an absolute frame, but you claim it's open to the idea,...

Where did I say that?

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I would have read his [Einstein's] words in context, bearing in mind the physics that went before him and the empirical nature of physics. If he simply said "you can't tell if you're moving", since I know that statement, taken in isolation, is demonstrably untrue, I would ask him more about what precisely he means by it.

It is not demonstrably untrue - it is demonstrably true. You cannot tell if you're moving because there's always a frame that says you aren't, and it could be right.

Given the standard definition of movement (change in the position of one object relative to another with respect to time) you can tell if you're moving. As I said, given that definition I would ask Mr Einstein what he meant. He would then tell me that what he was referring to was the old Galilean idea that the laws of mechanics, and the measurements from which they are derived, are invariant when measured against different inertial reference frames.

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A few pages ago, when I asked you some simple questions about it, here:

viewtopic.php?p=318878#p318878

in your answers here:

viewtopic.php?p=318986#p318986

you either didn't answer the questions or answered them wrongly.

I answered them correctly. You just don't like my correct answers because you prefer your incorrect ones which are informed by a broken theory.

Since the above is self-evidently false, there's nothing more I can really say here. All I can do is point you again to the standard definitions of words such as "acceleration" and "velocity".

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This seems odd because they're simple questions. Question 1, for example, could be on a high school Physics exam. But rather than simply giving the obvious answer you started going on irrelevantly about how "the universe supports only one underlying reality".

It's called precision rather than regurgitation of dogma. The answers that you want to hear are the ones based on shackled thinking rather than free rational thought.

It's not "shackled thinking" to simply recognise the definitions of the words "acceleration" and "velocity", to recognize that they are vectors and to know how to add two vectors together.

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This rings alarm bells for me. Maybe you somehow just misunderstood what the question was asking. But I don't see how. I tried to make it as plain and unambiguous as possible. It was a question about how a ball, thrown upwards, moves just after it leaves the hand that throws it.

Your question has a bias built into it that you cannot see because of the way you've been trained...

What bias? A bias towards the standard definitions of words in physics?!?

Maybe you somehow think it's a trick question? It's not! It's just about the most straightforward question in mechanics that I could possibly ask! Think about it. Suppose when the ball leaves your hand it's travelling at a velocity of 50 ms^-1, straight up, relative to the surface of the Earth. Do you accept that as a possibility? (I'm learning to take nothing for granted about the way that you think.) Now suppose that the acceleration due to gravity near the Earth's surface is 10 ms^-2, rounded to the nearest whole number. What will be the ball's velocity, relative to the surface of the Earth, after 1 second? After 2 seconds? What will the magnitude and direction of the ball's acceleration, relative to the surface of the Earth, be?

Again, this is not a trick question. There is no hidden agenda.

...If you say that the ball decelerates, you're assuming a particular frame to be the absolute one, but you don't know it to be the absolute frame, so saying that the ball decelerates is an assumption based on something that may be an error...

No I am not assuming that. In the above example, what is the speed (note: I said speed, not velocity) of the ball, relative to the surface of the Earth, after 1 second? After 2 seconds? What is the definition of the word "decelerate"? Now: Is the ball decelerating with respect to the Earth? Is its speed relative to the Earth reducing?

No tricks. No agenda.

...I'm not going to make a stupid mistake of that kind, but you think I should in order to conform to the stupidity you're pushing. I reject that stupidity. I do not give absolute answers to questions which I can't give absolute answers to without being able to measure the absolute, and the fact that you expect me to do reveals a massive error in your thinking.

Unbelievable.

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Do you accept that an object in free fall in the Earth's gravitational field is accelerating towards the centre of the Earth and can be moving upwards (have its velocity vector pointing upwards), with its speed (the magnitude of its velocity) decreasing?

Yes. If you want to word things that way, I have no problem with that. It doesn't make my way of wording things wrong.

?!? After all that talk of the "stupidity I'm pushing", you suddenly agree? How else would you word it?

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Do you accept that any object moving in a circle, at constant speed, is, by definition, accelerating towards the centre of that circle?

Yes, but I don't let that blind me to the fact that it could also be decelerating in an absolute frame (which is something you want to ban people from realising).

I don't want to ban anyone from anything. Obviously if the centre of that circle is itself moving relative to some other reference frame, then the orbiting object, in addition to accelerating towards the centre of the circle, is also moving relative to that other reference frame.

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Original question (paraphrased):
1. If I throw a ball upwards, neglecting air resistance, as soon as it has left my hand, is it accelerating, deccelerating or both?

The correct answer is not dependent on the coordinate system you're using, so the answer c is wrong. The correct answer depends on whether it's accelerating, decelerating, or doing one followed by the other, and that depends on its movement relative to the space fabric.

No. the correct answer is by definition that acceleration is the rate of change of velocity with respect to time, which means that it can result in the magnitude of the velocity increasing, reducing or remaining the same. If the magnitude of the velocity remains the same, but there is still a non-zero acceleration, then the direction of the velocity is changing and the two vectors are perpendicular to each other.

The correct answer is the one I gave you. You asked an absolute question and I answered it on that basis...

I asked you a question about a person throwing a ball while standing on the surface of the Earth. I said something about the velocity of that ball when it leaves the thrower's hand. I said it was "straight up". Are you really telling me that you didn't realise I was talking about the velocity relative to the Earth?

...Your inclusion of the word decelerating also implies that your usage of the word acceleration there excludes cases where something is decelerating...

No it doesn't. Acceleration is by definition rate of change of velocity WRT time, where both are vectors. Deceleration is by definition reduction in speed. A change in velocity can result in speed increasing, staying the same or decreasing. These things are true by definition.

...If you want your answer to be the correct one, you need to frame your question with greater care and spell out the definitions of the words you're using in it wherever they go against normal usage....

I was using all words according to their normal usage in physics. I was under the impression that we were having a discussion about physics.

...If told you before that the differences between our answers come down to one simple thing - you're asking absolute questions and demanding SR answers (i.e wrong answers) while I'm giving LET answers (i.e. correct ones), and I'm giving you LET answers because SR is broken and should not be given precedence over a rational theory that works.

I'll tell you again: this is nothing to do with SR or LET. It is pre-SR and pre-LET. It is part of the building blocks that you need in order to start tackling those subjects.


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So an acceleration vector pointing in the opposite direction to a velocity vector means that acceleration is a deceleration, if we define "deceleration" as reduction in speed, which seems reasonable.

This is basic, basic stuff which comes before SR or LET.

It is basic stuff, but if you keep asking absolute questions without realising that that's what you're doing, you're going to keep tripping up. You're mistaking your communication failures for mistakes in my understanding of physics - that is the root of your problem here...

I really wish that were true and we could establish that we've covered the basics of Newtonian mechanics so we could move on to SR and LET. But most of the evidence I've seen so far suggests otherwise.

...Did you ever bother to click through to my reference-frame camera program (from my relativity page)? Anyone who spends a few minutes exploring that should realise that it can only be put together by someone who really knows their stuff...

Then show me you know your stuff with your words.

...You're searching in the wrong direction. What you should be doing is defining your SR models and showing where they fit in with the ones I've identified. Then we can discuss each one in turn and I'll show you that every single one of them is broken. I can understand that you want to avoid going there, but that is what the invitation here is. If you're sure you have a model that stands up, why delay going straight for the kill. All I ask of anyone is to show me a working model of SR, but by heck it takes a lot of work to drag them towards that, and NONE of them can deliver.

No, we're nowhere near that yet.

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There's nothing "non-genuine" about a non-inertial frame....

There is. In the gravitational case they're fine, but when an object is actually accelerating, a non-inertial frame continually asserts that the speed of light relative to it in all directions is c, and that's a continual contradiction with the previous moment. Such frames are not valid in that they are automatically misrepresentations of reality.

And here is another example of the reasons why we're nowhere near it.

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For future reference: Please don't tell me what I'm seeking to do.

You are playing word games, and I will call that out every time you do it.

As I said: Take what I say literally and do not assume that I mean various different things that I didn't actually say. If I use a word and don't define it, assume I'm using that word in accordance with its standard definition in physics, because that is the subject we're discussing. If I talk about a person standing on the surface of the Earth throwing a ball upwards, then obviously I mean upwards relative to the surface of Earth, not relative to the surface of Venus or some kind of aether. If you still insist on telling me what I'm seeking to do, then it's not "calling me out" it's simply not reading what I said. If you're not going to read what I'm saying, there's really no point in trying to continue communicating with you.

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When I ask a question I am seeking to get from you an answer to that question, as it is stated. Nothing more.

You are applying a bias to them which you don't recognise.

And, of course, I can assert the same of you. And we'll get nowhere. Is that how you want the conversation to end?

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I asked you if you accept the fact that velocity and acceleration are vectors. This is because I am seeking to know whether you appreciate that velocity and acceleration are vectors. If you don't, then it's really difficult to discuss any aspect of physics because we don't speak the same language as each other. I'm just trying to establish whether we speak the same language.

And you're doing this because...?

For the reason I gave you in the words of mine that you just quoted! You give a very, very good impression, in your words, of someone who is muddled about these things. I wanted to give you a chance to prove my impression wrong.

...Why are you wasting time on that? It all came out of one little phrase which was transitioning from one idea to another one, momentarily mentioning acceleration and deceleration (but without that contrast being important to the discussion), and moving on to something much more clear cut involving the ticking of two clocks where both are asserted to be ticking faster than the other. So what do you do? You ignore the clocks, and fixate on the acceleration vs. deceleration issue instead. It is actually relevant, but it would be very hard for you to see how given the depth of your indoctrination. You've been taught that something can be accelerating and decelerating at the same time, and it would take a lot of work to deprogram you on that point, which is why I'm not going to bother trying. The ticking rate comparison is much harder to cover up through brainwashing though, because someone who believes that clock A can tick faster than clock B while clock B ticks faster than clock A is manifestly certifiable.

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By one very specific definition of the word, yes. It isn't necessarily a real acceleration though just because it's been given a label with a misleading name.

A label with a misleading name?!?!? This, perhaps more than any other answer, appears to me to demonstrate you lack of grasp of basic physics that it is essential to grasp if you're going to tackle more advanced subjects like SR and LET.

(This was exactly the kind of example which led me to conclude that you're confused as to what acceleration is and what a vector is.)

That's where you keep repeating the same mistake. You want me to answer absolute questions in a biased way which accepts SR and rejects the absolute frame...

I'll say it yet again: this has nothing to do with SR. It's pre-SR. There is nothing in the standard definition of the word "acceleration" that rejects that concept of an aether.

...I'm not going to let my brain function on such a bias - not for you, and not for anyone. Reason dictates that there must be an absolute frame (in some models) in order to remove the contradictions, and you want me to abandon reason...

In showing me that you accept the standard definition of the word "acceleration" I am not telling you to abandon the concept of aether. If you were clear as to what the word means, I would have thought you'd know that.

...You want me to parrot mantras from a religious cult instead of doing physics properly. Your cult has given its own definition to a word which I, as someone who is not a member of that cult, refuse to endorse. You are fully entitled to use the word the way your cult uses it and I do not question your understanding of physics on the basis that you do so. I am likewise entitled to use the word my way, and as it's the way that normal people outside of the cult use it, it should not be hard to understand...

So, to be absolutely clear on this point: You think that defining acceleration as rate of change of velocity with respect to time, and defining both of them as vector quantities is a "mantra from a religious cult"?

Jeez.

...When you ask absolute questions, I don't apply the unstated bias that you imagine onto it - I answer the actual question that's been asked. The difference between my answers and the ones you want does not reveal a lack of understanding of the physics on my part, but is actively driven by my understanding of the physics and my rejection of your cult. I am in the LET camp, and we have an absolute frame. When we talk about deceleration, we ruddy well mean a deceleration (where kinetic energy is actually being lost rather than gained). Otherwise, we're merely dealing with apparent deceleration.

OK. Noted.

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It is true by definition of the words "acceleration", "velocity" and "circle" that an object moving in a circle has an acceleration vector which points towards the centre of the circle. This a function of the definitions of those words. It's not specific to any individual aspect of physics that we might be discussing. Please tell me that I've misinterpreted you and you understand this bit of basic physics and geometry! If not, as I've said, we have no language in common in which to communicate.

It should be obvious from my answers that I don't accept your definitions as absolute ones. There are alternative ones which are preferable because they are more logical, and you should expect me to use those as standard. Your usage of some words puts a bias into them which allows you to frame things as absolute statements which are logically incorrect by the more rational definitions of the same words and which make precision harder. Your definitions actively warp your ability to understand what you're describing because of their inherent bias.

Yes, I'm starting to realise the full extent to which we don't speak the same language.

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Regardless of whether you think there is such a thing as aether, movement is by definition a function of the relationship between objects.

Movement (in the absence of any wording relating what it's relative to) is by definition movement relative to the absolute frame. You're using a biased definition in which the existence of the absolute frame is denied.

Nope. As I've said, you're more than welcome to talk about movement relative to an aether.

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If you think there is such a thing as aether then the sentence is rendered meaningful by changing it to: "object A is moving at 5 m/s relative to the aether". And, like any proposition in physics (or science generally) that proposition, to be meaningful, needs to be empirically falsifiable/verifiable, either directly or indirectly. i.e. you need to show how that statement is useful for describing and predicting possible observations.

It is meaningful in physics because not having an absolute frame generates contradictions and invalidates the model. Again though, instead of arguing over linguistics, you should be setting out your SR models and telling me where they fit into my set of models, or where you want to put them if you think they don't fit in my set. Then we can take each one in turn and demolish it.

I'm close to giving up now.

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David, based on our conversation so far, I think we're going to have to leave it. Not because we disagree about Special Relativity. We haven't go that far yet. You don't appear willing to accept the standard definitions of basic words. If you just keep refusing to do so, then we quite literally don't speak the same language. So I'll just have to say it's been ... interesting and leave it there. I presume you'll want to chalk this up as some kind of victory over some kind of dogma (the dogma of words having agreed definitions, I guess). Be my guest.

All the best.

Steve

[Steve3007]

https://www.britannica.com/science/acceleration