The meaning of absolute

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Catastrophe

The devil is in the detail
Helio, "Einstein's asking whether or not standing in an elevator in space represented a difference between acceleration and gravity gave us the greatest theory of all time -- GR."

Unless I am much mistaken, GR has passed every test thrown at it. This hardly warrants "swinging buckets" being compared with justifiable, testable, hypothesis.

Cat :) :) :)
 

Catastrophe

The devil is in the detail
Helio, I have no objections to mathematical suggestions providing that they carry a health warning. This should disclaim any connection with existing current science where appropriate.

From your previous postings, I consider that you are the best person to supply the health warning. Your previous posts carry all the necessary ingredients. ;)

Cat :) :) :)
 

Catastrophe

The devil is in the detail
"What would happen if external gravity is removed?" Meaning the Universe?

What would happen if we were to be hit by a comet ten times the size of the Chicxulub asteroid?

I think the latter is more likely.

Cat :)
 
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"What would happen if external gravity is removed?" Meaning the Universe?

What would happen if we were to be hit by a comet ten times the size of the Chicxulub asteroid?

I think the latter is more likely.

Cat :)
Well, since you asked. :) Contemplations of the first might help lead to preventing the second, and all future impacts. The converse won’t offer any scientific advancements from anyone left to do so. :)
 

Catastrophe

The devil is in the detail
I don't know how you would turn off gravity throughout the Universe, but if you could, would not all planets and anything orbiting anything, just zoom off in a straight trajectory (vide Newton) away from their life-giving stars? Even if they didn't collide, all life would be extinguished everywhere.
Anyway, if you kill off the whole Universe, except Earth, the result would be the same and for Earth also. So these mathematicians had better realise that, whatever they decide from observing a single spinning Earth, all life would be extinguished.
Tell them to wake up, because the reality is they cannot achieve it, and designing an experiment which cannot be conducted is futile.
Tell them to go off and do something useful, like guessing what would happen if they could change all the stars in the Universe into twins of the Sun, and guess what the distribution of life would be - would there be more seven legged Brontosaurus than eight legged possums.
I am sure they would find lots more interesting things of a similar nature which they could add to the list, and prosecute in the interests of science (Remember they are the mathematics
fans.)


Cat :) :) :)
 

Catastrophe

The devil is in the detail
Not turn off the Universe, but turning off (down) the gravity in a solar system: See post #55

All About Space Issue 118 12th June 2021 Worlds without suns
How rogue worlds are made
2. They're ejected by a supernova explosion
"When the most massive stars reach the end of their lives, a spectacular explosion sheds most of their mass and drastically reduces their gravity, potentially cutting loose any orbiting planets to fly off into interstellar space."

Cat :)
 
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If science were to discover, say, the hypothetical (thus active science) graviton and then discover an antigraviton (suppositional; not active science, AFAIK), then perhaps Mach’s test could be done in a lab. We do this regularly with things called lab models for impact studies or mag fields for planets.

Though we understand the effects of gravity, we still don’t know enough about gravity to say what we can and can’t know about it.
 

Catastrophe

The devil is in the detail
Helio, relevant to discussions about science v philosophy, I have found the following, with which I totally agree:

ABK2761.AllAboutSpaceAnnualVol7.pdf (futureplc.com)

"Combining theory and simulations with actual observations will help us get to the bottom of the mysteries hiding underneath Uranus’ deceivingly calm exterior. Maybe it’ll even teach us something about the whole universe of planets outside our Solar System, too." My emphasis.

Page 120.

I think where we differ is in the 'actual observations'.

Cat :)
 
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Helio, relevant to discussions about science v philosophy, I have found the following, with which I totally agree:

ABK2761.AllAboutSpaceAnnualVol7.pdf (futureplc.com)

"Combining theory and simulations with actual observations will help us get to the bottom of the mysteries hiding underneath Uranus’ deceivingly calm exterior. Maybe it’ll even teach us something about the whole universe of planets outside our Solar System, too." My emphasis.

Page 120.

I think where we differ is in the 'actual observations'.
Wow, 164 pages of info and illustrations! Nice.

Where do we differ?

Observations are a requirement. Theories need to predict observations as well. Direct observations are ideal, but indirect (circumstantial) can be equally effective if multiple lines of evidence converge.
 

Catastrophe

The devil is in the detail
What observations can we require regarding the first tiny parts of a second after t = 0 (for want of a better description)?
My impression is that we know nothing whatsoever about it and, imho, we probably do not have the vocabulary (or even brain architecture) to address it.

Cat :)
 
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What observations can we require regarding the first tiny parts of a second after t = 0 (for want of a better description)?
My impression is that we know nothing whatsoever about it and, imho, we probably do not have the vocabulary (or even brain architecture) to address it.
Agreed, science has something to say about our limits of possible observations when < 1 planck unit of time. This is where only pseudoscience or metaphysics keeps the door open.
 
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Catastrophe

The devil is in the detail
" This is where only pseudoscience or metaphysics keeps the door open."

Helio, you know that I only wish to promote friendly, amusing discussion.
It just seems to me that the 'authorised version' (scientific) of that time seems to point to a BB 'out of nothing'. This may well be my own ignorance or misunderstanding, so I am not pressing an issue, but asking a question. Does science promote an initial BB, or does it allow equally the possibility of a cyclic Universe. Sorry to have nominated you as the spokesman for 'science'! :) :) :)

Cat :)
 
The meaning of absolute

OK Just asking if we are done with this question?
No.

First, Many words in the dictionary have different meanings for different situations. I think there's been a misunderstanding of which version to use in this debate. I found the following to be absolutely perfect for the spin debate;

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

Second, I think people are also thinking that because something is absolute it means it has a one-off value such as 0 kelvin or c speed.

The above definitions can be applied to each body/planet separately. All planets can and do all have different rates of absolute spin. The 'absolute', means as per definitions above, that the unique individual spin of each planet is "not dependent on, conditioned by, or relative to anything else"

I was surprised to find the discussion of spin still going on here. I thought I'd found an article, post 45, which would conclude the debate, which I posted on the thread called;


This thread has been locked so just in case you have not seen it, please have a look. The article concludes that spin is absolute in all three categories;

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.”

Also in that thread I put forward my space station thought experiment which should help anyone get a 'feel' for why I think spin is absolute in post 10;


P.S. Since there is no way to measure spin, no external reference, you cannot claim that there is any spin at all. Relative to what?? You need my observer for that - then it is relative.
You do not need an external frame of reference to measure absolute spin. Spin causes centripetal force which is totally independent of what's going on in the rest of the universe.

Force (centripital) = mass x velocity^2/radius (velocity is radial velocity, ie spin)

All you need to do is measure the centripetal force on a known mass at the surface of the rotating object, and the radius of it, and you can calculate the radial velocity, ie absolute spin velocity. No reference is needed to anything external. (please see space station experiment link above).

So what about SPIN? Can spin be absolute? Is there a standard like 0 deg spin? Well, err, I can't find one. Does it make sense? Well, err, I don't think so.
Let us take planets X, Y and Z. They are spinning at different rates. Which one is the absolute standard of zero spin. This is clearly a non-question. There is no unique frame of reference to consider any one as spin = zero, which would be required of an absolute value.
I can see Catastrophe is needing a standard absolute zero spin as a reference.

If you check all the way around a body and find no centripetal force, then it's not spinning - there is your 'absolute zero spin'.

The only evidence I see from Catastrophe is about Machs principle from physicsstackexchange.com. This is not a science reference site, it's a chat forum where you can pick a discussion to back both sides of an argument.

No one has found anything wrong with my space station experiment, and I've provided a proper scientific reference article in the thread as per link above. Unless anyone can find a proper article, I suggest we conclude that;

SPIN IS ABSOLUTE
 
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" This is where only pseudoscience or metaphysics keeps the door open."

Helio, you know that I only wish to promote friendly, amusing discussion.
It just seems to me that the 'authorised version' (scientific) of that time seems to point to a BB 'out of nothing'. This may well be my own ignorance or misunderstanding, so I am not pressing an issue, but asking a question. Does science promote an initial BB, or does it allow equally the possibility of a cyclic Universe. Sorry to have nominated you as the spokesman for 'science'! :) :) :)
See if this helps, as many also struggle with a beginning.

Consider the actual and historical beginning for the Big Bang to be today, at t=13.8 Gyrs. Then, by rewinding the clock from today, we see what the universe looked like as density, temp., etc. changes. We keep going as far as science holds its parts (equations) together, which we then learn we can’t get to a t=0. It was 1927 when Lemaitre began that journey backwards. His original model, of course, became far more sophisticated but that first Planck second seems to be a genuine barrier.

Thus, BBT, in terms of actual hard science, cannot argue or demonstrate a beginning singularity. It is certainly hard to think it’s not inferred, but any inference only works within metaphysics or worse.

Perhaps something besides energy existed in a tiny spacetime-like region precipitating extreme energy and initiating expansion. But, of course, this is another example of metaphysics, or better. :)
 

Catastrophe

The devil is in the detail
"Spin can be observed relative to the 'fixed' star background. If spin of a planet is absolute, then the whole starry firmament must re rotating individually around every planet and each moon."

I suggest that the most appropriate dictionary to quote in a space forum is:
Oxford Dictionary of Astronomy, which gives:
"Rotation The turning of a body on its axis, such as the daily rotation of the Earth. It is usually measured relative to the stars, and termed the sidereal period of axial rotation."
My emphasis/

EOS

Cat :)
 
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Catastrophe

The devil is in the detail
David, you posted above:
"First, Many words in the dictionary have different meanings for different situations. I think there's been a misunderstanding of which version to use in this debate. I found the following to be absolutely perfect for the spin debate;" My emphasis.

I completely agree with the part I have emphasised in bold. However, what I find absolutely perfect in discussing spin/rotation of planets/moons on their axes, is the definition given in the Oxford Dictionary of Astronomy.

Since you seem to favour general definitions, which is your prerogative, I suggest that we agree to differ. Just leave any interested parties to choose their option, as is their prerogative. I cannot see any interest in further prolonging this subject here.
If you so wish, I am willing to proceed via 'conversation' or email but, to be honest, I cannot see the point.

Kind regards

Cat :) :) :)
 
Force (centripital) = mass x velocity^2/radius (velocity is radial velocity, ie spin)

This equation does not need any external reference frames or measurements and it is independent of anything else going on in the universe.

If you apply this equation to a rotating body, eg another planet or a space station you will get an answer for the radial velocity. You only get one answer you do not get a separate answer if you come from Earth or if you come from Mars. I ask is this an absolute answer or is it relative? if you think it is relative then tell me what it is relative to. You can radio this answer to inhabitants of Earth or Mars and it will be the same answer for both, meaning it is absolute.

This equation is not my opinion it is high school physics and could be understood by any schoolchild.

In addition to the above equation, I have provided a good scientific article from Wikipedia, via post 63 above, which states that classical mechanics, Isaac Newton, Special relativity and General relativity all say that rotation is absolute.

According to said article Catastrophe seems to me to be going against both Isaac Newton and general relativity.

Above are not my opinions they are real science. So far all I've had from catastrophe is mostly his personal opinion without any good backup articles.

I recommend to everyone to accept the implications of the equation and the contents of the Wikipedia article and so accept that

SPIN IS ABSOLUTE

- until catastrophe or someone else can provide a good article that specifically says rotation or spin is not absolute or is relative. So far no one has done this.
 
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I see no reason not to treat spin as absolute. It fits all force results including the Coriolis Effect and why hurricanes/cyclones spin the way they do.

Newton’s laws of gravity also are treated as absolute, though Einstein introduced changes given certain circumstances. These changes alter the centripetal force equation for satellites since angular velocity is a function of time.

The absoluteness of the fixed speed of light is a result of the absolute values for certain constants, as discovered by Maxwell.

So does the equation for centripetal force depend on the mass of all the stuff a rotating body sees going around it, or is that force all but eliminated if this body is alone in an empty universe?

The real question, perhaps, is does it matter either way since the Universe is out there? Or are there different degrees of “absoluteness”? Perhaps, but why bother?
 
"Spin can be observed relative to the 'fixed' star background. If spin of a planet is absolute, then the whole starry firmament must re rotating individually around every planet and each moon."
Yes, Spin CAN be observed relative to the 'fixed' star background. What does that prove? What fixed stars? I do accept they are as good as fixed, just making a point. If you look up from any planet long enough of course you will see the stars moving round, what does that prove?

I find it's weak evidence.

I suggest that the most appropriate dictionary to quote in a space forum is:
Oxford Dictionary of Astronomy, which gives:
"Rotation The turning of a body on its axis, such as the daily rotation of the Earth. It is usually measured relative to the stars, and termed the sidereal period of axial rotation."
My emphasis/

EOS
"It is usually measured........." You can measure it how you like, but it won't take away its true instantaneous absolute value of spin. I say instantaneous because planets have variable mass distribution due to tides and magma etc. Absolute spin is a property, even though it's not always possible to measure it using centripetal force.
 
Yes. Mach's principle seems to be the defining question to whether or not spinning can be considered absolute.
If anyone wants to cling onto Mach's principle, read further down in that article and it becomes a bit dodgy;

"But because the principle is so vague, many distinct statements can be (and have been) made that would qualify as a Mach principle, and some of these are false."

"Most physicists believe Mach's principle was never developed into a quantitative physical theory that would explain a mechanism by which the stars can have such an effect. It was never made clear by Mach himself exactly what his principle was.[7]:9–57 Although Einstein was intrigued and inspired by Mach's principle, Einstein's formulation of the principle is not a fundamental assumption of general relativity."

"Because intuitive notions of distance and time no longer apply, what exactly is meant by "Mach's principle" in general relativity is even less clear than in Newtonian physics and at least 21 formulations of Mach's principle are possible, some being considered more strongly Machian than others.[7]:530 A relatively weak formulation is the assertion that the motion of matter in one place should affect which frames are inertial in another."

"There have been other attempts to formulate a theory that is more fully Machian, such as the Brans–Dicke theory and the Hoyle–Narlikar theory of gravity, but most physicists argue that none have been fully successful."

However, even if one wants to play imaginary philosophy, then it seems that Einstein-Mach came out on top anyway.
"Einstein later abandoned the principle when it was realized that inertia is implicit in the geodesic equation of motion and need not depend on the existence of matter elsewhere in the universe."


Nonsense exposed?
 
Practical example of absolute zero spin;

Beautiful pictures from the Hubble telescope of course!

Pictures from the most distant galaxies can take exposure times of 2 weeks, with just 1 photon arriving per 1/2 hour.

How could this be possible unless the telescope adjusted to absolute zero spin. I think zero here means a 0 with a big string of 0's after the decimal point!
 

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