Question Does everything in space spin - does the Sun spin ?

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I am not playing games like 'you do this if I do that'.

I have made my case, you choose, sadly it seems, to prevaricate, I have asked to clarify assumptions - specifically - we just seem to speak different languages.

There are no winners. We shall both enjoy our assumptions.
Have fun. Live long and happily.

Best wishes,

Cat :)
I was very sad to see this reply, I was so much looking forward to someone commenting on my example.

I'm sorry I annoyed you and that you took my last post in a way not intended by me. I was a little clumsy, I'm not as good with words as you. My intention was to be extra polite giving you an easy option not to reply. Perhaps I should have done what some other people do, i.e restate my case and then shout WHAT'S WRONG WITH THIS........ with big bold and coloured underlined letters.

I just wanted one last chance for someone to comment on my example, before I started commenting on your examples. I wasn't playing games, I was just trying to be methodical. I notice that you even have to ask for peoples opinions about your ideas. In post 17, you say "Helio, what is your take on this?" It's nice to have people comment on one's ideas, that's all I wanted.

As for assumptions, I thought I had addressed that with the definition of rotation etc. That did cover differences between day and night and year, spin and orbit. All in post 22. I'm sorry for being too thick see anything else that needed clarifying. What other assumptions did you want clarifying?

I made no extraordinary assumptions in my space station example.

1. You know how an artificial gravity space station works.

2. There are only the usual scientific assumptions in the formula I used. It's a standard formula for centripital force, I didn't make it up.

It was crystal clear, I used plain English with readily available definitions on google etc.
 
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If you know your mass, and the radius of the space station you can calculate your absolute rate of spin without looking out of the window, by using the formulae;

Force (centripital) = mass x velocity^2/radius

In this equation, the force, the mass and the radius are absolute values, so the velocity term must also be an absolute value.
All three terms (mass, vel., radius) will change with different inertial frames, in accord with relativity.

I think your point of them being essentially absolute is reasonable as engineers rely on this to make things work properly, but this is only true for their respective inertial frames.
 
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Quote
Rotating Coordinates in Relativity
Relativity is built on the existence of inertial frames. . . . . . . . . . The first thing relativity does with an inertial frame is define coordinates for it. These coordinates are meaningful: in particular, the time coordinate is constructed such that two events in the frame that have the same time coordinate will be measured by all inhabitants of the frame to occur at the same time. Other coordinates can be constructed that don't obey this idea. These other coordinates have limited value because, in particular, two events that occur simultaneously might be allocated different values of such a time coordinate.
Quote

Helio, what is your take on this?
The above makes sense to this novice. I regularly fall back upon the train drawing revealing time change between the ground observer and the one on the train.

So, if time tics differently for every inertial frame in relative motion, it’s an imperative different results will be timed differently. But transform equations can easily resolve things so that things like lighting strikes make sense.

Another example is one’s use of a yard stick’s use vs. a meter stick, the values will be different but, after conversion, exact agreement is easily obtained.
 
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David, there is very little ABSOLUTE in this world and, sorry, to disagree with you, but spin (imho) ain't one of them. Absolute with respect to what absolute reference standard?
A spinning object may be stationary and surrounded by a spinning Universe. (Careful!)

"My research showed that spin and orbiting or revolving are both different kinds of rotation. I still think both are absolute values." No. Sorry. Quite different - imho. My emphasis.

Please think again before night and day alternate too many times. They do, you know.

Cat :)
Absolute with respect to what absolute reference standard?
Absolute to nothing!

That what absolute means!

It does not need to be referenced with respect to anything!

A spinning object may be stationary and surrounded by a spinning Universe. (Careful!)
A spinning universe will NOT alter the weight you see on the bathroom scales and therefore the spin velocity in my space station example. I already said the calculation of spin is not dependant on external factors

Come to think of it, how would a rotating universe even affect the spin of the earth? Would it alter the length of day and night? No, because its spin is an absolute property.

"My research showed that spin and orbiting or revolving are both different kinds of rotation. I still think both are absolute values." No. Sorry. Quite different - imho.
No, not different. Orbiting is also an absolute property, because you still use the same equation for centripetal force, so the orbit velocity is only dependant on gravity force, the mass of objects and distance from the common axis.
 

Catastrophe

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David, if you know me at all, you will know that I do not criticise people, only ideas
Do you call the following other than rhetorical?

* The Earth spins once in 24 hours wrt Sun. Now add Venus, which spins retrograde. Which is absolute - Sun, Earth or Venus? You have 3 relative spins S-E, S-V, and E-V. Which is absolute? And if you say Sun - then see above - which "Sun"? *

I tried to find some basis in assumptions, on the basis of which we might proceed. I could not. I found only (IMHO) only something incomprehensible. Therefore I decided that there was no common ground on which to continue.

Perhaps you might like to comment on the * paragraph * above, as to whether it is rhetorical. Please note that (unusual for me) I have put is instead of consider or think. In other words, is it a statement of fact that that all 3 cannot be absolute? Or, if you select Sun, then please see above regarding variable spin rates of our star.

You posted (#26) "I was very sad to see this reply ". I hope that you are happier than this one. It is not common knowledge, but I was selected by a major scientific publisher to edit a volume on my specialist subject. I really do have a lot of experience in carefully composing, checking, and correcting what I write. Now someone will find an obvious error in spelling or grammar, and I shall be extremely embarrassed. :) :) :) :) :)

There you are: "You have 3 relative spins S-E, S-V, and E-V"
Which is absolute? Or is S absolute? Or are they all absolutely hopelessly lost in an absolute chaotic mess of semantic inexactitudes?

Cat :)
 
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A spinning universe will NOT alter the weight you see on the bathroom scales and therefore the spin velocity in my space station example. I already said the calculation of spin is not dependant on external factors.
You may be correct, and I favor this view,but good luck demonstrating that claim. :)


Come to think of it, how would a rotating universe even affect the spin of the earth?
It would have the same effect as we observe now with a rotating planet. That’s how GR works. A modified Tychonic model has never been falsified, but it was dismissed at its conception, even by Kepler who worked with Tycho, and it was politically favorable with most church theoLogan’s who were stuck on Aristotle’s Geocentric model. Copernicus, however, gave us both elegance and unification in his model.


No, not different. Orbiting is also an absolute property, because you still use the same equation for centripetal force, so the orbit velocity is only dependant on gravity force, the mass of objects and distance from the common axis.
Ok, but a space traveler going, say 99% c, will absolutely disagree. So why use the term “absolute”?

iPad
 
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Well, sorry, I will continue.
We know that the Sun spins differently at different latitudes. The core also spins differently. It is not an absolute frame of reference. Just suppose that the Sun did spin uniformly despite latitude or composition. There is an absolute frame of reference? No.
Just consider a trillion such "Suns" all spinning uniformly.
Where is the absolute frame of reference? Which "Sun" is the correct one?

Cat :)

To continue (if t'were necessary?) consider Earth orbiting Sun. Assume 'perfect' Sun as above.
The fact that Earth spins in approx 24 hours has no connection with the time it takes to orbit the Sun. (Quote me the Kepler Law which contradicts this - or any other law).
So Earth spins once in 24 hours wrt Sun. Now add Venus, which spins retrograde. Which is absolute - Sun, Earth or Venus? You have 3 relative spins S-E, S-V, and E-V. Which is absolute? And if you say Sun - then see above - which "Sun"?
Just suppose that the Sun did spin uniformly despite latitude or composition. There is an absolute frame of reference? No.
You do NOT need any frames of reference to determine spin velocity or orbit velocity. How can I make it clearer that you only need force, distance and mass for the centripetal equation!!!
So Earth spins once in 24 hours wrt Sun. Now add Venus, which spins retrograde. Which is absolute - Sun, Earth or Venus?
All of them!!!

Each has its own unique absolute value of spin, independent of each other.
 

Catastrophe

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IMHO there are certain words, adopted in mathematics, which should be recognised as meaningless, or, worse, highly deceptive, if employed outside a mathematical arena. Viz. absolute, infinity . . . . . . . . .

Cat :)
 
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Catastrophe

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You do NOT need any frames of reference to determine spin velocity or orbit velocity. How can I make it clearer that you only need force, distance and mass for the centripetal equation!!!
All of them!!!

Each has its own unique absolute value of spin, independent of each other.
Sorry David. I cannot continue with any discussion which assumes that everything is absolute.

Cat :)

P.S. I already disposed of the pseudo suggestion calling on relativity to bail out statements that it did not make.
 
David, a key seems to be:
'The "Yes. Relative to something." reply was a red flag for me :). I think it's fair to challenge something I don't agree with, also it's still about spin.'

That speaks to definitions, so let's try and clear it up.

I cannot see the problem with everything spinning relative to something.
Earth spins relative to Sun, hence day and night.
Venus spins retrograde. Relative to Sun, its spin is different. Venus spins relative to Earth - maybe better to say Earth spins relative to Venus. All spin is relative to an observer situated on another body (or anywhere). What is wrong with that?

Cat :)
That speaks to definitions, so let's try and clear it up.
I can't understand your obsession with definitions? All the words and formula in my space station example are standard from google etc.
Earth spins relative to Sun,
Venus spins relative to Earth
No Earth spins - full stop

No Venus spins - full stop
All spin is relative to an observer situated on another body (or anywhere). What is wrong with that?
Appearance may change from planet to planet but that doesn't change the measurable absolute spin of a planet as made by an occupant of it, which can be communicated to another planet.
 
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Catastrophe

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"David, agree to leave it there." Meaning between us only,

Please feel free to r*g*r*i . . . . . . . . . never mind. I don't speak that language either

Cat :)
 
All three terms (mass, vel., radius) will change with different inertial frames, in accord with relativity.

I think your point of them being essentially absolute is reasonable as engineers rely on this to make things work properly, but this is only true for their respective inertial frames.
Yes, but the manufacturer of the space station will have made it in a reference frame 'still' relative to all the parts, and so should be able to provide a rest length (if there's such a thing) of the radius. Also, the person in the space station will have previously been able to determine their rest mass on a planet. Ahh! stop that person might eat something, so better put a known rest mass inanimate object on the bathroom scales instead (as per my space station example).

The question is, is there such a thing as an exact rest mass and rest length? I would say yes in classical mechanics, but as for relativity, I can't say.

Also, the only thing that matters is the reference frame on the space station. As the person there will not be referencing anything outside of it. It doesn't matter what anyone else measures from another external frame.
 
You may be correct, and I favor this view,but good luck demonstrating that claim. :)


It would have the same effect as we observe now with a rotating planet. That’s how GR works. A modified Tychonic model has never been falsified, but it was dismissed at its conception, even by Kepler who worked with Tycho, and it was politically favorable with most church theoLogan’s who were stuck on Aristotle’s Geocentric model. Copernicus, however, gave us both elegance and unification in his model.


Ok, but a space traveler going, say 99% c, will absolutely disagree. So why use the term “absolute”?

iPad
Not sure what you mean here because I don't know how GR works!
Ok, but a space traveler going, say 99% c, will absolutely disagree. So why use the term “absolute”?
I agree, but the person flying past the space station and the orbiting planets will be using a different method of calculation. Directly measuring the rotational velocity with optical, laser or radar instruments etc. The person on the planet or in the space station is calculating the rotational velocity by making different measurements, ie using force, mass and length. It's not a fair comparison, it not comparing like with like. So I would stick with the term 'absolute' for the person using the centripetal force method.

Overall, I don't know how relativity works in this case, I'm just hoping I've thrown a spanner in your arguments. :) :):)

Would you at least agree that rotation is absolute in classical mechanics, and if so, would that mean anything, given that relativity has superseded classical mechanics?:)
 
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The question is, is there such a thing as an exact rest mass and rest length? I would say yes in classical mechanics, but as for relativity, I can't say.
GR can offer no absolute frame. Indeed, it was established to falsify traditional thinking their is one.

But, there may likely be a preferred frame...the Hubble Flow. Essentially all galaxies are in this flow and their clocks would, generally speaking tic at the same rate.

Also, the only thing that matters is the reference frame on the space station. As the person there will not be referencing anything outside of it. It doesn't matter what anyone else measures from another external frame.
Agreed. But I tend to get muddled with rotating frames since rotation introduces acceleration (angular). It’s not hard to understand, IIRC, but I rarely find interest in it.
 
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Overall, I don't know how relativity works in this case, I'm just hoping I've thrown a spanner in your arguments. :) :):)
I’m quite limited in my understanding of GR, but I’m fairly adept at grasping some of its tenets since they help explain much.

History may prove fruitful....
With SR (1905), many, but not a majority, of physicists saw a train wreck coming their way. Einstein and Eddington in particular saw it. Once you accept e=mc^2, then if their were to be such thing as absolute space then anything in motion would have more energy, thus more mass.

So, imagine another exact copy of the Solar system but one closer to the galactic center, would Krpler’s laws, or almost any law produce the same results for either system? No, the inner solar system twin would have the star and planets as more massive, so they would necessarily revolve faster. But the MW is also moving, complicating things further.

Einstein, apparently, was convinced that the laws of physics, including similar results, should work for any reference frame. GR accomplishes this, which is why Eddington was quick to learn it.

One of the results of GR is that any point can be picked for a center. Hence, the Earth can be treated as the center of the universe and be in full compliance with modern physics. [This was my point about a modified Tychonic model being valid.]

But, notice GR allows for any point to be a center, which implies nothing special for the Earth as a center. [Fictious forces are also an issue, btw.]

CB Would you at least agree that rotation is absolute in classical mechanics, and if so, would that mean anything, given that relativity has superseded classical mechanics?:)
The irony, perhaps, is that relativity eliminates its own use for engineers for the reasons stated above, ignoring GPS and whatnot.
 
"David, agree to leave it there." Meaning between us only,

Please feel free to r*g*r*i . . . . . . . . . never mind. I don't speak that language either

Cat :)
<<Removed by moderator>>

To help you with any language problems, I've found the following definitions of 'Absolute' for you;

MERRIAM-WEBSTER;
5a:
independent of arbitrary standards of measurement

Cambridge Dictionary;
true, right, or the same in all situations and not depending on anything else:

but in absolute terms (= without comparing it with anything else)

certain; not to be doubted:

dictionary.com;

something that is not dependent upon external conditions for existence or for its specific nature, size, etc. (opposed to relative).

Oxford Languages;
viewed or existing independently and not in relation to other things; not relative or comparative.

a value or principle which is regarded as universally valid or which may be viewed without relation to other things.

something that exists without being dependent on anything else.

Collins English Dictionary;
not dependent on, conditioned by, or relative to anything else;

not dependent on, or without reference to, anything else; not relative

IMHO there are certain words, adopted in mathematics, which should be recognised as meaningless, or, worse, highly deceptive, if employed outside a mathematical arena. Viz. absolute, infinity . . . . . . . . .

Cat :)
Seems to be ABSOLUTELY the perfect word

All spin must be relative.
There are no absolute rotations,
David, there is very little ABSOLUTE in this world and, sorry, to disagree with you, but spin (imho) ain't one of them.

ABSOLUTE ROTATION;


From the article;

CLASSICAL MECHANICS
“Newton's conclusion was that rotation is absolute.”

SPECIAL RELATIVITY
“Rotation was thus concluded to be absolute rather than relative.”

GENERAL RELATIVITY
“there appears to be absolute rotation relative to these stars.”

Note the use of the word rotation, which includes spin and orbiting!

Sorry, in my vocabulary, this: "each has its own unique absolute value " is meaningless non sequitur.

Cat :)
Since rotation is absolute and since the values of rotation are different for each object – each must have its own unique absolute value!

One is still free to compare any rotation relative to any other rotation, but that won't take away its true absolute value!
 
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