If geocentrism, then what observations would differ on a "truly" sun-orbiting body?

[George]

As per Mach's viewpoint, which I think has a lot to be said for it, it simply makes no sense to adjudicate the question "which one is really moving" at all-- it's not an argument between whether you move within the universe, or the universe moves around you, it's recognizing that there is not even one single solitary difference between those perspectives.

That makes sense especially from a kinematic point of view but other observer's makes the claim silly. Yet, I concede that it is only "silly" when we add a given and obvious frame of reference. A driver that claims his car can go over 1100 mph at the equator will look silly, Eppur si muove veloce.

The motion is a relationship between you and the universe-- you may as well argue whether the groom marries the bride or the bride marries the groom.

Yes, but in this case, all the observers will agree that these two are the ones getting married but will disagree strongly that the universe only dances to my dance, though they would not argue the kinematics of my claim, I suppose. Eppur.....

I would say the strong claim, only. With respect to the weak version, their objective evidence actually supports it, not negates it.

Yes, that's a fair point. The negation of the Ptolemy model came from the observation of both crescent and gibbous phases for Venus (and Mercury), but Ptolemy would have seen these as well if he had had Galileo's telescope.

-- it is like saying that every time someone fights for their own legal rights, they are indirectly supporting my own legal rights too, not negating them. The "right" they are fighting for is the right to adopt a language that is every bit as consistent with the laws of physics as some other more common language-- vive la difference.

Yes, it just seems odd that the blatant difference is a claim of invariance.

There does seem to be some difference there-- I've heard the claim that GR succeeds in complete translational relativity of motion, but not rotational. I really don't know if that's true, and if it is a flaw in GR.

You've addressed this a few times including in the above posts and the gist I'm getting is that in translation we can assign any speed we want to an object simply by locating ourselves at the appropriate locations that allows that observation, but if we want to observe, for instance, the Earth's orbital motion around the Sun to be zero we would then have to continaully accelerate ourselves in a synchronous orbit -- I refuse to sit on the Sun -- and this introduces your Machian question. Am I close?

[Ken G]

Yes, but in this case, all the observers will agree that these two are the ones getting married but will disagree strongly that the universe only dances to my dance, though they would not argue the kinematics of my claim, I suppose.

But the analogy still holds-- all observers will agree the bride and groom are marrying, all observers will agree the Earth and the universe exhibit relative motion. Any attempt to adjudicate the question any further may be leaving the realm of science altogether-- they won't agree the universe is dancing when you dance, but they also need not agree that the universe is holding still. Holding still relative to what? Motion is relative, that's its meaning. It's not a democracy where if 99 people think someone else is moving, and 1 person thinks it's the other 99, the 99 have to be right. I'd feel the same way in a society where 99 people think the groom marries the bride and 1 thinks the bride marries the groom-- I'd say it's an interesting sociological study to ask that question, but the reality of the marriage is a relationship which has nothing to do with who we say is doing the marrying.

Yes, it just seems odd that the blatant difference is a claim of invariance.

In the strong case, yes, and that is falsifiable-- they are claiming an invariant that does not exist. But the weak claim turns the invariance around-- it says that any language that produces all the correct invariants is as valid as any other. It's the difference between fighting to have one's own view, versus fighting to tell everyone else there's is wrong-- the latter requires a much different standard of evidence. Personally, I think both sides in the standard geocentric debate are wrong-- the "right" approach, pedagogically, is to adopt neither a categorically geocentric nor a categorically anti-geocentric approach, but instead treat a frame of reference the way it was meant to be treated-- as a tool for generating a language that can lead us to the correct observables.

You've addressed this a few times including in the above posts and the gist I'm getting is that in translation we can assign any speed we want to an object simply by locating ourselves at the appropriate locations that allows that observation, but if we want to observe, for instance, the Earth's orbital motion around the Sun to be zero we would then have to continaully accelerate ourselves in a synchronous orbit -- I refuse to sit on the Sun -- and this introduces your Machian question. Am I close?

Actually, I think the orbit of the Earth around the Sun presents no problems to relative motion-- I believe GR is perfectly Machian in regard to orbits, or any kind of translations. I think the problem is in the Earth's spin, which is a different category of motion. I don't think standard GR is Machian in regard to spin, but this is an area that requires more expertise than I have. There are other flavors of GR also, like Einstein-Cartan, which I believe attempted to make spin Machian as well, but I just don't really know a thing about it.

[Lenoxus]

Wow, I'm glad so much discussion was prompted by my question. It seems that that's bound to happen every time this topic comes up…

Anyway, I can't personally think of much else to add to it. As I said earlier, if experiments repeatedly find no unexpected difference for observers on other planets, then self-proclaimed strong-geocentrists are just going to deny space travel anyway, until perhaps the day comes when average citizens can afford to go there themselves.

What's more fun, therefore, is to imagine the crazy universe where the unexpected results do happen, seemingly confirming strong-geocentrism after all. Well, I should say "fun" for me, being someone with only a superficial acquaintance with physics and cosmology. If the science is sufficiently enmeshed with your brain's "common sense" understanding of the universe, finding evidence radically in contrast to the known science might be a tad more distressing.

(I probably wouldn't be excited to crack open a chicken egg and see something purple and bumpy; I'd be plain freaked. Conversely, my subconscious ignorance of some scientific matters is bliss. However, I'm ultimately happier with more knowledge than less, even if the tradeoff is that I can't properly enjoy movie scenes that have sound in space, etc.)

[Strange]

Well, I should say "fun" for me, being someone with only a superficial acquaintance with physics and cosmology. If the science is sufficiently enmeshed with your brain's "common sense" understanding of the universe, finding evidence radically in contrast to the known science might be a tad more distressing.

I would say any sort of new revelation like that would, perhaps, be even more exciting for those deeply involved in the physics. It would be like expecting a chicken to hatch from an egg and getting a golden goose!

[Ken G]

Yes, that's well put-- I'd say scientists have a love/hate relationship with being wrong!

[caveman1917]

Yes, that's well put-- I'd say scientists have a love/hate relationship with being wrong!

Indeed, i love being wrong and hate it when someone else gets the honour

[wd40]

Sir Fred Hoyle said "If the Galileo Affair had taken place after Einstein had framed his General Theory, it would have resulted in an even draw out of physical and mathematical necessity".

Did this Englishman, President of the Royal Astronomical Society, know what he was talking about?

[Ken G]

Sir Fred Hoyle said "If the Galileo Affair had taken place after Einstein had framed his General Theory, it would have resulted in an even draw out of physical and mathematical necessity".

Did this Englishman, President of the Royal Astronomical Society, know what he was talking about?

In my opinion, there is one very important way in which Hoyle is right here, and another very important way in which he is wrong. It really depends on whether one thinks the "Galileo Affair" was about deciding if the Earth was the stationary center of the universe, or if it was about deciding if the Earth was fundamentally different from the rest of the "heavens." In regard to the first issue, it would have been a draw, but in regard to the second issue, which is the much more important issue in my view (and was the important issue for people of Galileo's day as well), Galileo and Copernicus still win hands down. Indeed, that victory is today called "the Copernican principle."

[wd40]

Anything that smacks of a "preferred axis" is contra the Copernican Principle?
http://www.science.unsw.edu.au/news/...-physics-vary/

[George]

But the analogy still holds-- all observers will agree the bride and groom are marrying, all observers will agree the Earth and the universe exhibit relative motion. Any attempt to adjudicate the question any further may be leaving the realm of science altogether-- they won't agree the universe is dancing when you dance, but they also need not agree that the universe is holding still. Holding still relative to what? Motion is relative, that's its meaning. It's not a democracy where if 99 people think someone else is moving, and 1 person thinks it's the other 99, the 99 have to be right.

If I say "I am spinning", the universe can not spin since I have already stated that it is me spinning. If I say I was standing still and all of a sudden when I forced my muscles to make me turn the entire universe began to spin around me including the most distant objects, which must have known I was going to spin in advance given that it takes time for their light to reach me. We don't really need 99 others to verify that it would they are observing is counter to what I just claimed. But is this a strong or weak geocentrist view? We agree this makes since in the strong sense, but in a weak sense I have to be a little more careful with my phrasing, I think. I can say I spin and, as a result, the universe spins around me, which will be what you experience if you spin. Or, stronger still, the universe spins around me or I am spinning and I have no definitive way to say which it is based on GR, assuming some Machian understanding, perhaps. This later case still seems silly because it is so close to the strong version and other observers will disagree if they assume any position in the universe except that of the spinee, not to mention the wild and crazy causation issues regarding accelerating hundreds of billions of galaxies instantly. Nevertheless, perhaps something interesting will come from this suburb of Sillyville.

I'd feel the same way in a society where 99 people think the groom marries the bride and 1 thinks the bride marries the groom...

Ok, that's a clever lick.

Actually, I think the orbit of the Earth around the Sun presents no problems to relative motion-- I believe GR is perfectly Machian in regard to orbits, or any kind of translations. I think the problem is in the Earth's spin, which is a different category of motion. I don't think standard GR is Machian in regard to spin, but this is an area that requires more expertise than I have. There are other flavors of GR also, like Einstein-Cartan, which I believe attempted to make spin Machian as well, but I just don't really know a thing about it.

I had assumed movement about any axis would qualify.

[Ken G]

Anything that smacks of a "preferred axis" is contra the Copernican Principle?
http://www.science.unsw.edu.au/news/...-physics-vary/

That finding sounds pretty preliminary. If it holds under closer scrutiny, that's a Nobel prize for sure. But right now, on the surface it looks like "gee, two different telescopes see two slightly different things, must be the laws of physics that are different." That's going to take a lot of corroborating evidence to buy that one!

[Ken G]

If I say I was standing still and all of a sudden when I forced my muscles to make me turn the entire universe began to spin around me including the most distant objects, which must have known I was going to spin in advance given that it takes time for their light to reach me.

There's no actual problem with that scenario-- when your muscles act, they begin to put you into an accelerating frame. But acceleration is equivalent to gravity, so if you take as an axiom that you cannot move, that gravity instantly fills the universe. There is no causality violation there, because you could never use that fact to send a superluminal signal, and that's actually the only requirement relativity is able to assert. When the gravity fills the universe, it causes the rest of the universe to begin spinning around you. For a truly Machian theory (and I've heard it said that GR tried to be that but never quite succeeded, but if not, it could perhaps be fixed up), the form of the equations are completely ambivalent to whether you view the observer as moving, or the observed as moving. The laws themselves tell you the issue is completely moot, it's all what you add to the laws to suit yourself. And note, you can go either way to suit yourself-- for some like you, you find it too absurd to imagine the rest of the universe responds to your every whim. But that's a very realist perspective. For those who adopt a more idealist perspective, that their own personal reality is the only reality that will ever really mean anything to them, they might be quite fine with the idea that it is impossible to move themselves, they can only move their perceptions. Then there are the middle-of-the-road types, like myself, who like to borrow the best of both realism and idealism, who say that if the equations don't know the difference, there isn't any difference, we are just imagining there is a difference because we have adopted an extraneous ontological stance somewhere along the way.

A key point in all this, which separates it from strong geocentrism, is that we must take the view that the laws exist to help us understand and predict what we perceive, not to determine what is actually happening. When physics is seen as a primarily subjective undertaking that respects certain key objective criteria, then weak geocentrism, which is really just a Machian view, follows somewhat naturally. Indeed, on second thought, I find myself surprised that Einstein could have been such a die-hard Machian, yet at the same time such a die-hard realist-- those don't seem like compatible stances to me.

I had assumed movement about any axis would qualify.

I don't think so, because an orbit around an axis is instantaneously just a combination of a lateral translation and a radial acceleration. It's all linear motion, just the acceleration does not align with the velocity. But spin is different. It's true that a spinning object has each of its parts in an orbit of sorts, but there is one key difference-- not only are the parts of a spinning object moving in a circle, they are also themselves spinning. Those are two separate motions involved in a spinning object. Put differently, you could orbit the Sun but not spin, sort of like Venus does. Spin is something different, and it is much harder in GR, and it is the area that GR might not even have gotten right (for all we know-- last I heard, Gravity Probe B had some problems and was not able to deliver the confirmation it had hoped for).

[George]

There's no actual problem with that scenario-- when your muscles act, they begin to put you into an accelerating frame. But acceleration is equivalent to gravity, so if you take as an axiom that you cannot move, that gravity instantly fills the universe.

Well, I have been known to exercise.

Yet, it is horribly counter intuitive to suggest I can perform such feats. Think how much they would have laughed at anyone asking Newton if it was the Earth instead that had arisen to his apple. But it is unfair to not consider the possibility you suggest, and it is still in accord with GR (caveat for Mach), given the lack of any objective evidence, apparently, countering the "absurd" claim. For this reason, I admit to waxing philosophically and outside true science.

I do think "absurdity" comes from our natural propensity to attach to reference frames. Apples fall rather than await the rise of the Earth because, to us, the Earth is a solid and fixed frame, at least relative to any apple. The Hubble Flow is possibly another frame we are attracted to, at least, but there is no clear reason yet why it deserves any special significance given the acceptance of GR.

And note, you can go either way to suit yourself-- for some like you, you find it too absurd to imagine the rest of the universe responds to your every whim.

Georgecentricity, admittedly, does have a nice ring to it, and being silly or absurd at times, though extremely rare, is not beyond me.

But that's a very realist perspective. For those who adopt a more idealist perspective, that their own personal reality is the only reality that will ever really mean anything to them, they might be quite fine with the idea that it is impossible to move themselves, they can only move their perceptions. Then there are the middle-of-the-road types, like myself, who like to borrow the best of both realism and idealism, who say that if the equations don't know the difference, there isn't any difference, we are just imagining there is a difference because we have adopted an extraneous ontological stance somewhere along the way.

Agreed, though I am respectful of your view knowing that it can easily be today's absurdity that becomes the staple in tomorrow's scientific diet.

A key point in all this, which separates it from strong geocentrism, is that we must take the view that the laws exist to help us understand and predict what we perceive, not to determine what is actually happening. When physics is seen as a primarily subjective undertaking that respects certain key objective criteria, then weak geocentrism, which is really just a Machian view, follows somewhat naturally.

Yet Nature is real, though she is clever and more indeterminant than expected. Ok, I know, what really is "real"? Fair enough.

Indeed, on second thought, I find myself surprised that Einstein could have been such a die-hard Machian, yet at the same time such a die-hard realist-- those don't seem like compatible stances to me.

True, but he did prefer "invariance" over "relativity".

I don't think so, because an orbit around an axis is instantaneously just a combination of a lateral translation and a radial acceleration.

Ah, that helps. Thanks.

[wd40]

Why should the universe do it's darndest to seemingly conspire against the direct detectability of the earth's motion? It is GR itself that is giving the modern geocentrists a rope to cling to. Should GR ever be proved to be wrong, could that rope suddenly become a reinforced tower?

[George]

Why should the universe do it's darndest to seemingly conspire against the direct detectability of the earth's motion?

It isn't hard to see that the Earth is in motion, but there is no known unique reference frame so you have to ask "relative to what?", apparently. This question becomes so much harder since the speed of light is always measured to be the same speed no matter what reference we pick, so this presents a problem but it also helps point us in the right direction, no doubt.

It is GR itself that is giving the modern geocentrists a rope to cling to.

KenG has simplified this with his "strong and weak geocentrism". Those that are claiming the strong version should well know that GR does not demonstrate any preferential frame.

Should GR ever be proved to be wrong, could that rope suddenly become a reinforced tower?

It would likely depend on how GR failed. Strong Geocentrism made a lot of sense prior to Galileo's telescope. It makes little sense now given the discovery of over 130 billion other galaxies and all the other local evidence suggesting planets orbit their more massive host star.

[wd40]

If GR failed, how would the results of Airy, Michelson-Morley and other experiments likely be explained, without invoking geocentrism?

[George]

If GR failed, how would the results of Airy, Michelson-Morley and other experiments likely be explained, without invoking geocentrism?

I assume that it would depend on how GR failed. If spacetime is localized for the M-M table (no aether flow on Earth's surface), for instance, then the null result makes sense, I think.

[Lenoxus]

Why should the universe do it's darndest to seemingly conspire against the direct detectability of the earth's motion?

The main reason, I think, is that the Earth loves us sooo much that it's been unwilling to let us go without some trouble.

Once we're all grown up and left the nest, we'll have the necessary distance to see that, though they do love and respect us very much, the universe never revolved around Mom and Dad the Earth.

[Jens]

If GR failed, how would the results of Airy, Michelson-Morley and other experiments likely be explained, without invoking geocentrism?

I think it depends on what you mean by "fail," or rather, in what way. For example, Lorentz explained it without GR, but Einstein's solution was seen as more elegant, in a sense.

[publiusr]

On a whimsical note, I have always wanted an orrery of the actual Copernical system, but with the base attached to a large Earth globe instead of the sun, so its mounted like a Ptolemaic but runs Copernican. I don't know that it is buildable.

[George]

On a whimsical note, I have always wanted an orrery of the actual Copernical system, but with the base attached to a large Earth globe instead of the sun, so its mounted like a Ptolemaic but runs Copernican. I don't know that it is buildable.

That sounds like a Tychonic model.

Here's a whimsical drawing of what one might look like!

BTW, I have tossed in an erroneous touch. Can anyone see it?

[Celestial Mechanic]

That sounds like a Tychonic model. Here's a whimsical drawing of what one might look like! BTW, I have tossed in an erroneous touch. Can anyone see it?

I don't see our Moon, Luna, anywhere.

The thing that has always bothered me about the Tychonic models is the fact that they show the Sun (and the planets that orbit it) orbiting about the center of the Earth, NOT the Earth-Moon barycenter. Strange, isn't it that in this supposedly "geocentric" model the only things that directly orbit the Earth are the Moon and the Earth's artificial satellites. Why does everything else in the Universe orbit the Earth-Moon barycenter? If the Earth is "special" or "privileged" then the Moon must be too, if only less so.

[HenrikOlsen]

I don't see our Moon, Luna, anywhere.

The thing that has always bothered me about the Tychonic models is the fact that they show the Sun (and the planets that orbit it) orbiting about the center of the Earth, NOT the Earth-Moon barycenter.

The Tychonic models came before any theory of gravity, so the concept of a barycenter was unknown.

[Ken G]

Is the flaw, in addition to leaving out the Moon, not tilting Uranus on its side?

[wd40]

Here modern geocentrists have made their own orrery



http://www.geocentricity.com/bibastr...ry/orrery1.pdf

[Hornblower]

I don't see our Moon, Luna, anywhere.

The thing that has always bothered me about the Tychonic models is the fact that they show the Sun (and the planets that orbit it) orbiting about the center of the Earth, NOT the Earth-Moon barycenter. Strange, isn't it that in this supposedly "geocentric" model the only things that directly orbit the Earth are the Moon and the Earth's artificial satellites. Why does everything else in the Universe orbit the Earth-Moon barycenter? If the Earth is "special" or "privileged" then the Moon must be too, if only less so.

The Earth's motion about that barycenter would displace the apparent positions of the planets by only about the diameter of Mars from their mean positions. Tycho was doing naked eye sightings, which were incapable of detecting such motions even at a close approach of Mars.

[Hornblower]

Addendum to prior post: If we so wished, we could build an enhanced Tychonic orrery with the Moon orbiting a stationary Earth, and with the Sun orbiting a point which is under the Earth's surface and in conjunction with the Moon. The planets could be mounted in gymbals that would allow them to spin at their observed tilts.

[wd40]

If one assumed that GR and SR are wrong and that there is an ether, then the modified Tychonic model might actually explain all the astronomical observations and all the null-velocity experiments the best of all models!

[George]

I don't see our Moon, Luna, anywhere.

Ooh, I had intended to get her in there along with another prominent satellite....Done.

The thing that has always bothered me about the Tychonic models is the fact that they show the Sun (and the planets that orbit it) orbiting about the center of the Earth, NOT the Earth-Moon barycenter.

What am I, a Texas Leprechaun?.....Done.

Strange, isn't it that in this supposedly "geocentric" model the only things that directly orbit the Earth are the Moon and the Earth's artificial satellites. Why does everything else in the Universe orbit the Earth-Moon barycenter? If the Earth is "special" or "privileged" then the Moon must be too, if only less so.

Perhaps they’d say, “Equants are quaint and apply to all.”

The Tychonic models came before any theory of gravity, so the concept of a barycenter was unknown.

I assume the equants were their equivalent, which might explain the origin of this odd term since there were few Barry’s in their day. [Wow, I’m going off the deep end already.]

Is the flaw, in addition to leaving out the Moon, not tilting Uranus on its side?

That’s a reasonable observation, but you’re not taking into consideration the George-centric nature of the question, though the intrinsic smirk was withheld.
Inclination change.... done!

[Hornblower]

If one assumed that GR and SR are wrong and that there is an ether, then the modified Tychonic model might actually explain all the astronomical observations and all the null-velocity experiments the best of all models!

The challenge is to develop a dynamic theory that would explain the motions. Newton found a simple formula for gravity that works for a heliocentric model, and Einstein largely cleaned up the discrepancies that became observable after Newton's time. An analogous theory for a Tychonic model might not be impossible, but it would be a horrific kludge by comparison. I cannot think of anything short of an orrery built with invisible mechanical cranks and levers.