Strange

That seems to be an overly simple description; after all, they don’t kill their own cubs. They don’t kill other moving things such as butterflies and lizards. And if they have just eaten, they won’t even attack prey.

No. The observer effect is about how our measurements affect what we are trying to measure. It can apply to almost anything (for example, putting a voltmeter across a circuit changes the behaviour of the circuit). It can also apply to a single measurement, while the uncertainty principle relates two measurements. The uncertainty principle is about the limits to how accurately we can know something, even with perfect measurements: "The uncertainty principle has been frequently confused with the observer effect, evidently even by its originator, Werner Heisenberg.[18] The uncertainty principle in its standard form describes how precisely we may measure the position and momentum of a particle at the same time — if we increase the precision in measuring one quantity, we are forced to lose precision in measuring the other.[19] " https://en.wikipedia.org/wiki/Observer_effect_(physics) I'm not sure that is a useful example. After all, particles have momentum (and waves have position). But it does, perhaps, relate to the fact that the uncertainty principle is based on Fourier transforms between the two things being measured. And not sure why this is in Philosophy as it is purely a matter of physics.

I meant to say, the equations are the theory. The calculations are the application of the theory. Good. Now is the time to present it.

I have no idea. It would be crazy. So why would you want to derive relativity "without respecting the first postulate"? The calculations are the theory. To support that claim, you would need some evidence. Do you have any? (No, you don't.)

If you want to, you can take this into account in your calculations but in most case it is not significant. It is important for people to be aware of this though: https://en.m.wikipedia.org/wiki/Observer_effect_(physics) note that this implicit in the first postulate of SR.

The slight irony there is that Feynman won the Nobel Prize for his contributions to quantum electrodynamics (QED) and yet he went on to do a series of lectures to lay audiences (also available as a book) which did explain the concepts in simple terms that almost anyone can understand.

The normal assumption for unqualified mass nouns is that they apply to some members of the group (I read an article by a linguist about this recently, but can't find it now). For example, "people are afraid of heights" is a statement of existence; it means that there are some people who are afraid of heights. It would need a qualifier for [most] people to think it applied to everyone.

I see absolutely nothing wrong with using "purpose" to describe a function with no intention behind it. For example, saying "the purpose of breathing is to provide oxygen and remove CO2" or "the purpose of ribosomes is to translate RNA to proteins". And, as you admit that it is what "everybody says" then that is the meaning of the word, like it or not.

OK. It may not have been a criticism, but it was John's post you quoted, rather than the person who quoted the sentence originally. I don't. I was under the impression you did. Sorry if I misunderstood your desire to correctly represent Einstein's words. This is all unnecessarily off topic. So shall we drop it now?

What is the source for this? Does it include dark matter? It looks like it does include dark matter: https://en.wikipedia.org/wiki/Milky_Way#Size_and_mass So by simulating a mass distribution that includes dark matter to obtain the observed rotation curves, you appear to have confirmed the dark matter hypothesis. Well done.

If you want criticise anyone for that, it should be beecee, not John. You know, if you are being really pedantic. We are all wrong at some time! Science is the art of being constructively wrong (someone famous said something along those lines). Edit: It was Feynman, who said: "Science is the belief in the ignorance of experts." Not quite the same thing. But he also said, more relevant to this thread: "Hell, if I could explain it to the average person, it wouldn't have been worth the Nobel prize." https://en.wikiquote.org/wiki/Richard_Feynman

He was just correcting the grammar in beecee’s post, not trying to give an authoritative version of the original. But I’m sure everyone appreciates your work in that respect. That is true for simple things. And (as the original was about physics) I think it would be fairly easy to explain, say, Newton’s laws to almost anyone. The basic concepts of more complex ideas can be explained in simple terms. But you soon run into the problem that people will only have a limited understanding. In the case of GR or the Higgs mechanism, their understanding will probably based on analogies of limited accuracy. This isn’t normally a problem. Except when people think they have a proper understanding and either attempt to disprove it or create their own theories based on their limited understanding.

Your first “postulate” is not a postulate of relativity (apart from the fact that the “real” first postulate says it applies to all inertial frames of reference). And, obviously, if you derive something that contradicts Newton’s laws, then you will get a result that doesn’t work in the real world. However, SR does work in the real world. So what is your point?

I don’t see how they contradict one another. That first postulate is for the case where there are no forces - Newton’s other laws explain how to account for the effects of forces. So if you want to take the forces into account you need to do the appropriate calculations. And yet it works.

No, let’s stay focussed on the need for mathematics and evidence. Of what theory? And as we can observe them, and even use them in technology, they are not just theoretical. They are all too brief to be meangful as support of your claim m without the mathematics and evidence. Obviously. But hard to see how this is relevant. Symmetry groups are mathematics, too.

But ... you said you weren't talking about scientific truth ... now you are saying it is scientific truth ... But now you are saying it isn't scientific truth ... ? I think you need to clarify what you are saying. (And using different colours, sizes and block caps doesn't help clarify it.)

So you are saying that is not "scientific truth"? (even though it is, according to Einstein, what science is seeking) Just to be clear, I am asking this because you said:

Please show the mathematics behind this claim.

Ah, I see what you mean. That's the trouble with being cryptic: people are likely to misunderstand you. I though you were claiming that there are two spatial dimensions and two time dimensions (I suspect others did two). But it seems that all you are doing is separating the two dimensions affected (in a specific case) from the other two. But what if the object is not moving in just the x direction? What if it moving in x, y and z? Then it is contracted in all three spatial dimensions and lengthen in the time dimension. And what difference does your model make? Is the mathematics different? Does it make different predictions from SR?

So what sort of truth are you talking about? I did. It seems an odd statement so I had nothing to say about it. So if someone disagrees with the content of the links, you will just ignore them? So you only want to discuss with people who agree with the article? Is that right?

No one asked you to. Only people who know nothing about science say that. Nothing in your top post provides any support for your claim. As you are unwilling/unable to provide any support for your idea (and it contradicts known physics) we can just assume it is wrong.

It is explained fine by existing theory (which is based on 3+1 spacetime). Perhaps you can provide some mathematics and evidence to support your idea?

It is in the title though. And yet you reject the discussion that has taken place.

Took me a while to find that quote because in this translation, this sentence is slightly different: "If the theory corresponds to the facts, radiation conveys inertia between the emitting and absorbing bodies." https://www.fourmilab.ch/etexts/einstein/E_mc2/e_mc2.pdf But that doesn't make a material difference. You haven't said why you think that there should be a force or why you think there is a contradiction. Are you thinking of the momentum of the radiation or conservation of momentum or something else?

But if that mass distribution doesn't match what we observe, then it isn't very useful. It is not clear if your program reproduces the actual observed velocities or just the shape of the rotation curve. If it is the former, then you must be deducing more mass than we actually observe. which is where dark matter comes in.