The meaning of absolute

Catastrophe

The devil is in the detail
In my ignorance, I thought this was obvious:

adjective
.not qualified or diminished in any way; total.
total, utter, out-and-out, outright, entire, perfect, pure, decided, thorough, thoroughgoing, undivided, unqualified, unadulterated, unalloyed, unmodified, unreserved, downright, undiluted, solid, consummate, unmitigated, sheer, arrant,rank, dyed-in-the-wool, plenary, peremptory

Well, that seems to me that absolute means something unique, complete in itself, not something shared with every other atom in the Universe.

So let's play devil's advocate/ There is absolute temperature. This has temperature values corresponding to other temperature scales, but it is based on a unique temperature value 0 K. It is also given a fixed Centigrade equivalent -273. something Centigrade.

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. Consider two spheres side by side. Their spin or rotational axes are parallel (in this example). Let us suppose that their rotational spin about each axis is equal. Then it will be rather like Earth and Moon. Apart from a little libration we always see (from Earth) the same side (face) of the Moon.

With two bodies it is possible to have exactly corresponding spin. Normally spin is a property of one body only. Rotation (ambiguous word), lets say orbiting requires two bodies or, at least, one body and some imaginary centre of orbit.

Let us be quite clear. Mass is a property unique to any body. This does not stop massA being more than massB and less than massC. There is an order in their properties. Similarly spin (rotations around the axis of one body) may seem different to different observers. There is a specious argument about the galaxy orbiting one body. This is not what relativity is about, and it has been disposed o elsewhere. 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. Forget the planets. Is their star an absolute standard of spin? Is their star stationary? not spinning? It is clearly ridiculous to suggest that one star in the Universe is stationary - is not spinning. There is no absolute value of spin - no standard star whose spin = zero.

So does every moon, planet, star, galaxy . . . . . . . . . have an absolute value of spin? Is every one the standard for which spin = zero? Does every galaxy revolve around its every star? Does the Universe revolve around each speck of dust? This is clearly ridiculous - a total negation of the concept of absolute.

I think it would take a suggestion, that the issue is confused by definitions, to obfuscate the issue. Without definitions, what are we left with? A confused jumble of words better suited to a totalitarian manifesto? This is not science. It is mumbo jumbo better suited to . . . . . . . . . well, I won't go there. I'll leave it to you to work out.

Sorry about the length of this post. I believe that it is important to avoid meaningless words in our discussions. Words like infinite and absolute belong in mathematical textbooks, not in the real world.

Cat :)
 
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Catastrophe

The devil is in the detail
I have seen it stated (in a forum) that spin (day) is absolute, and somehow connected with orbital period (year). I have been unable to understand this and post the results of my investigation below. For outer planets I used a factor of 365 days conversion. This introduces an error of about 0.07% if anyone wants to be that fussy :) :) :)
Data from Google.

Can anyone see any connection whatsoever? Please let me know if you do.

Planet​
SPIN day hours​
ORBIT year days​
Jupiter
9.9​
4380​
Saturn
10.7​
10585​
Uranus
17.2​
30660​
Neptune
16.1​
60225​
Earth
23.9​
365​
Mars
24.6​
687​
Mercury
1407.6​
88​
Venus
5832.5​
225​
 
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Catastrophe

The devil is in the detail
As a further example of absolute, I would like to consider spin. Despite the discussion above (#1) I have seen some reasoned discussion on whether a planet's spin is absolute.
In this context I would like to suggest consideration of Mars.
This has been prompted by an article "Why is Mars continuing to wobble? by Alex Konopliv in All About Space Issue 115 April 2021.

I found it interesting that only two planets show a Chandler Wobble. Wiki gives the following with regard to Mars: (There is detailed discussion on Earth).

Quote
Chandler wobble of Mars

Using radio tracking observations of the Mars Odyssey, Mars Reconnaissance Orbiter and the Mars Global Surveyor spacecraft, the Chandler wobble of Mars has been detected. It is the first time it has been detected on a planetary body other than the Earth. The amplitude is 10 cm, the period is 206.9 ± 0.5 days and it is in a nearly circular counterclockwise direction as viewed from the North Pole.[6]
Quote

The Chandler Wobble - YouTube
https://www.youtube.com › watch


The Chandler Wobble. 506 views. 20. 1. Share. Save. Report. Kavya Devgun. Subscribe. Comments • 6. 8:17 ...
11 Dec 2019 · Uploaded by Kavya Devgun

In the context of absolute, how can such a planetary spin be regarded as in any way absolute? If some planets have Chandler Wobbles, which are absolute and which not? In what some might regard as a relativistic view (not I), consider Mars as centre of the Universe, and imagine the whole Universe engaging in a stuttering variable rotation around Mars. If there were any "absolute" frame of reference (don't blame me for that word!) an observer would see Mars spinning in about 24.6 hours relative to the stars, with a superimposed Chandler Wobble. Seen from any planetary body, Mars would be seen to be spinning relative to the position of the observer. This would be different for any observer anywhere. From Jupiter, spinning at roughly 2.5 times Mars, Mars would rise and set about 2-3 times a Jupiter day. Etcetera . . . . . . . . . . . . . . .

Please feel free to disagree with me if you will - I respect the right of anyone to have their own opinion - but I cannot see planetary spin to be in any sense absolute.

Cat :) :) :) :) :)
 
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It seems to me that planetary spin is a function the the planet's composition during formation, subsequent bombardments , changes in on the planet's surface and random asteroid strikes, all under the Sun's gravitational influence. E.G.: From a brief news item. When China built the Three Gorges Dam, it was reported that the Earth's spin slowed by some fraction of seconds. I don't see a connection to an orbital period.
 
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Catastrophe

The devil is in the detail
I took "its sidereal rotation period the time that the object takes to complete a single revolution around its axis of rotation relative to the background stars,"

sam85geo - Mercury and Venus particularly show the effect of asteroid collisions, although virtually every planet has suffered impacts,

I think that alone precludes any correlation between spin (day) and orbit (year_.

Cat :)
 
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I think some have confused rotation (spin) and orbital revolution (orbiting). One is not necessarily related to the other, the Earth could be spinning at any rate in the same orbit. But, relative v absolute? Imagine the Earth spinning as it is now, we can measure the decrease of weight on a given mass due to the spin rate, a few grams less compared to a non spinning earth. If we upped the spin rate high enough, we could fly off as it overcomes gravity. OK, now we have the concept. Now, let’s take away the rest of the universe, but keep the Earth spinning. Day/night goes away, the tides go away, but, I believe the gravity v spin force remains the same. However, we have no way to measure it as there is no absolute to measure against. We could just think that the acceleration due to gravity is just a bit less than we think now. Spin would be absolute, we just measure the rate, ergo, the spin force against what we perceive as stationary, the rest of the detectable universe. If that makes any sense.
 

Catastrophe

The devil is in the detail
"One is not necessarily related to the other"

They are clearly not related to each other. Several planets in our Solar System have been struck by large bodies - probably during the Late Heavy Bombardment.
Mercury lost most of its mantle, Venus had its spin reversed, Earth was hit by Theia to form the Earth-Moon system . . . . . . . . . How can the mass and velocity and angle of an impactor, producing a specific result (spin), be related to the orbital characteristics? Remember Kepler's Third Law? (The ratio of the square of an object's orbital period with the cube of the semi-major axis of its orbit is the same for all objects orbiting the same primary). Any collision would have caused the spin/orbit characteristics before and after impact to be quite different. In the case of Venus, for example, spin was reversed.

As for the rest "If that makes any sense." It doesn't.

If you are having recourse to "taking away the rest of the Universe" there would be nothing left but Earth in an expanse of nothing. How does a total fiction form as the basis for anything? You take away the Universe, I supply an external observer, and we have spin again - relative to my observer. Do you think that your scenario is better than mine?

Cat :)

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.
Furthermore, it seems to me that you are contravening Mach's Principle: **A very general statement of Mach's principle is "local physical laws are determined by the large-scale structure of the universe".** By removing the rest of the Universe, you are invalidating the local physical laws so determined.
 
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Catastrophe

The devil is in the detail
This (physicsstackexchange.com) deserves a frame of its own:

Quote
. . . . . . , the Einstein/Mach viewpoint holds that rotation is not relative to space, but rather is defined relative to the matter in the universe. If this viewpoint is correct, you would never see any precession of the pendulums because the bulk of the matter in this experimental universe is the planet itself, so it basically defines the frame of zero rotation.
Quote

Clearly, this invalidates your removal of the rest of the Universe. If you remove the rest of the Universe, then the bulk of the matter is in the planet itself, so it basically defines the frame of zero rotation. Ergo, the planet is not rotating as per your suggestion.

Cat :)

P.S. The following is reproduced from All About Space Issue 115 April 2021 in the Ask Space question, answered by Dr George Spagna. "Rotating" is here taken as spin (rotation about planet's axis) and not orbital motion.
" . . . while Jupiter and Saturn rotate once every ten hours. Among the planets, only Venus and Uranus fail to share this common rotation. Venus rotates backwards - or it's tipped upside down - while Uranus is tipped so its axis is close to the plane of its orbit. We believe these are due to violent collisions then the Solar System was still very young."
 
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Catastrophe

The devil is in the detail
Here is something which may amuse you:
Oxford Dictionary of Astronomy Ian Ridpath OUP 2011.

Quote
spin
A property of many subatomic particles, which behave as though they are spinning as they have angular momentum that is additional to any orbital angular momentum. However, since there is no way of marking a particle to observe its rotation, this property should not be taken too literally. . . .
Quote

Funny. No mention of planets. Thought this was an astronomical dictionary. Let's try planet and satellite . . . . . .

Quote
planet
A non-luminous body in orbit around the Sun, or another star . . .
Quote My emphasis.

Quote
satellite
A small body which orbits a larger one . . . . . .
Quote My emphasis.

Well, that seems to settle the orbit part.

Let's try revolve, revolution . . . . . .

Quote
revolution
The movement of one body in orbit around another, or around a common centre of mass, . . . . . .
Quote (e.g., Moon around Earth, Earth around Sun).

Well, let's try rotation . . . . . .

Quote
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.
Quote

That seems clear. But common parlance has otherwise.

So far the Oxford Dictionary of Astronomy has rotation = spin of one body about its axis (OK worry about precession, nutation and aberration elsewhere please)
AND
orbit means A small body which orbits a larger one . . . . . .
revolving = orbits . . . . . . one body around another.

One body spins/rotates about an axis (even if the axis wriggles ;)
Two bodies show one body orbiting or revolving around another.

Are we getting anywhere?

Cat :)
 

IG2007

"Don't criticize what you can't understand..."
Apr 5, 2020
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I am going to be really frank here, Cat.

Every single word in every single language has a basic abstract meaning behind it which you need to understand. For example, the words "is", "on" and many other words in many other languages. I find it a futile attempt to forcefully take each and every word from languages and try to give it a proper meaning when we actually know within ourselves what it means.

:) :) :)
 
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Catastrophe

The devil is in the detail
The point of language is to be able to communicate by assigning meanings to words. These meanings are supposed to be assigned, such that words allow these meanings to be shared. Of course, no definition is perfect, but if we do not accept dictionary assigned meanings, then communication will cease to function properly.

Of course, the map is not the territory, and words are not their definitions, Nonetheless, words are the only universal means of communication. They can be mass produced in papers and books, posted on the Internet, sent by telegram or telegraph or email to any place where there is a receiver.

Is what you are suggesting within this framework?

Cat :)
 
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The point of language is to be able to communicate by assigning meanings to words. These meanings are supposed to be assigned, such that words allow these meanings to be shared. Of course, no definition is perfect, but if we do not accept dictionary assigned meanings, then communication will cease to function properly.
Some words deserve special attention because of what it communicates to others. The word "absolute" is one of those word because it often is intended to draw a line in the sand. It is powerful and, because people want to appear powerful, it is overly used and abused.

"Absolute" is a word that is a square peg in the round hole of science. For instance, gravity, when expressed in scientific/mathematical form, may appear as something absolute, but Einstein changed that. When one claims something to be absolute but found to be otherwise, the more foolish that person looks, possibly diminishing both respect for that person and science itself.
 

Catastrophe

The devil is in the detail
""Absolute" is a word that is a square peg in the round hole of science."

I agree. It is another mathematical abstraction.
However, it does have limited usage = absolute zero (0 K)
But, of course it is still imaginary because you can never reach 0 degrees Kelvin.

Cat :)
 
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""Absolute" is a word that is a square peg in the round hole of science."

I agree. It is another mathematical abstraction.
However, it does have limited usage = absolute zero (0 K)
But, of course it is still imaginary because you can never reach 0 degrees Kelvin.
Yes, I think "absolute zero" is acceptable because it is inconceivable that one can go below that temperature. Adding the adjective should have proper impact, but it might not if it becomes common. It should be used objectively not subjectively, which may be partly how the Sun got saddled with "yellow". :)
 
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Catastrophe

The devil is in the detail
Helio,

Yes, I think "absolute zero" is acceptable because it is inconceivable that one can reach that temperature.

I changed your statement slightly, as indicated by the emphasis :)
For that reason, I omitted quotation marks.

Cat :)
 
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Catastrophe

The devil is in the detail
IG, absolutely correct. There always has to be a potential difference before anything flows.
Water will only flow downhill. If you want to heat something, you have to expose it to something hotter. If you want to cool it, you have to expose it to something colder. So it is trying to "pull yourself up by your bootstraps" trying to get something colder than the thing you are trying to cool.

Cat :)
 
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So, in post #6, when I said 'not necessarily related to the orbital period', I was thinking in terms of rotation can be tidally locked like the moon or Pluto/Charon, or in a simple resonance such as Mercury's 3:2, then the rotation is related to revolution, but, otherwise, they are independent. Given enough time in the life of our solar system, the tidal drag of the sun on the earth will eventually cause the earth to become tidally locked or in some sort of resonance. So would each of the planets on out. But, the sun will puff up and swallow the earth long before that. And the earth will heat up and become uninhabitable even before that due to increase in solar flux.

Then, to the original question whether spin is relative or absolute, a one-body universe is purely a thought experiment. Mach's principle where a particle alone in a universe cannot have spin or motion because there is nothing to compare them to, well, that seems to be still an open debate even today, from what I've read. If the single particle is the Earth, ignoring the fact that if there is no sun, the Earth would be a frozen wasteland without heat and light, but, since this is a thought experiment, we'll say the Earth is like it is today, just without a universe. If one can consider that if there is no external frame of reference, we could still have an internal frame of reference, the observer (the great minds in history we have had). The observer on the Earth's surface could carefully measure the distance of each latitude line and determine that the Earth is an oblate spheroid and can determine that it was caused by spin, and even roughly calculate the spin. Eventually, the observer and team members could eventually launch a rocket into orbit and determine the spin rate from the orbital period vs. where a single point of the ground is after one complete orbit. I kinda think the observer would eventually come up with the same math that we did to describe celestial physics as we know of it today. OK, so maybe without an observer, there would be no spin as there is no frame of reference (the observer in his/her wisdom and observaations), but, in Newtonian physics, to conserve angular momentum, it wouldn't make any difference whether there is an observer or not, the spin is still the same. This is sorta like the age-old question 'If a tree falls in the woods with no one around, does it make a noise?' It depends of your notion of sound . . . is it the vibration of molecules in the air or is it the reception of vibrating molecules on the eardrum? Without being able to duplicate this experiment in this universe, I tend to lean toward the Newtonian notion of spin.

But, this is a good question!! A real thinker.
 
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