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Illusory loops vs actual loops.



 
 
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  #1  
Old May 15th 18, 07:18 PM posted to sci.astro.amateur
Gerald Kelleher
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Default Illusory loops vs actual loops.

The geocentric astronomers since the time of the Greeks observed that while the Sun appeared to travel through the background stars directly, all planets would occasionally process a loop against the background stars -

https://apod.nasa.gov/apod/ap100613.html

Copernicus determined the direct/retrogrades were an illusion caused by the faster Earth overtaking the slower moving planets

https://apod.nasa.gov/apod/ap011220.html

The faster moving Venus and Mercury and their direct/retrograde motions are entirely different as they process a real and actual loop around the parent Sun hence their loops are not illusory -

http://www.insideastronomy.com/index...-venus-phases/

It would be helpful for those who show up in classrooms or at those star parties to enjoy how we see the faster and slower moving planets from a moving Earth and distinguish what are illusory looping motions from what are the normal circuits of the planets around our parent star.
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  #2  
Old May 15th 18, 09:45 PM posted to sci.astro.amateur
palsing[_2_]
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Default Illusory loops vs actual loops.

On Tuesday, May 15, 2018 at 11:18:57 AM UTC-7, Gerald Kelleher wrote:

The faster moving Venus and Mercury and their direct/retrograde motions are entirely different as they process a real and actual loop around the parent Sun hence their loops are not illusory -


This claim of yours, of course, is incorrect. Sure, Mercury and Venus make loops in the evening and/or morning sky "with respect to the Sun" over the course of weeks (Mercury) or months (Venus), but nevertheless, they ALSO make 'apparent' loops and zig-zags with respect to the background stars, just like the superior planets! See this page...

http://www.nakedeyeplanets.com/movem...uperiorplanets

Towards the bottom of this page, under the paragraph heading "The Inferior Planets", you will see this graphic...

http://www.nakedeyeplanets.com/mercu...r-oct-2023.png

.... which shows the motion of Mercury against the background stars for the year 2023. Also find this explanatory statement...

"The inferior planets also describe loop and zig-zag formations against the background stars, however unlike the superior planets these formations cannot be observed with the naked-eye since they take place when they are too close to the Sun. The motions of the inferior planets are therefore somewhat academic, however since they provide a more complete picture of planetary movements in the zodiac it will be of interest to examine them closer."

Finally, look for the graphics near the bottom of this page...

http://www.nakedeyeplanets.com/venus...htm#8yearcycle

.... to see the (5) different kind of loops that Venus makes, with respect to the Sun, in the evening sky at various latitudes over an 8-year cycle. They look nothing like the loops shown in your own reference, which mainly shows the phases of Venus and is NOT representative of the actual 'real' loops as you like to think exist.
  #3  
Old May 16th 18, 05:26 AM posted to sci.astro.amateur
Quadibloc
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Default Illusory loops vs actual loops.

On Tuesday, May 15, 2018 at 2:45:07 PM UTC-6, palsing wrote:
On Tuesday, May 15, 2018 at 11:18:57 AM UTC-7, Gerald Kelleher wrote:


The faster moving Venus and Mercury and their direct/retrograde motions are entirely different as they process a real and actual loop around the parent
Sun hence their loops are not illusory -


This claim of yours, of course, is incorrect. Sure, Mercury and Venus make
loops in the evening and/or morning sky "with respect to the Sun" over the
course of weeks (Mercury) or months (Venus), but nevertheless, they ALSO make
'apparent' loops and zig-zags with respect to the background stars, just like
the superior planets! See this page...


As I've been trying to explain, even if Oriel isn't getting the terminology or
the nuances quite right, what he is expressing here is the actual astronomical
truth of the matter.

Jupiter takes 12 years to make a complete circle of the Zodiac, as seen from the
Earth - and, as seen from the Earth, it loops around due to retrograde motion
multiple times during that period.

Jupiter's orbit around the Sun has a 12 year period - so the overall trend of
its apparent motion is "real", due to its orbit around the Sun - and the
retrograde loops are "illusions", a result of the Earth's orbit around the Sun
changing our point of view.

Mercury, on the other hand, takes exactly *one* year to make a complete circle
of the Zodiac, as seen from the Earth - because it never gets very far from the
Sun as we see it from our vantage point.

The retrograde loops in that one year circle around the Earth... reflect
Mercury's actual motion around the Sun.

So in this case, Mercury's real motion - its orbit around the Sun - creates the
loops in its apparent path from the Earth... and the illusory motion caused by
the change in our point of view by the Earth's motion causes the big overall
circle in which the loops are situated.

So indeed the apparent motion of the inferior planets is, in a sense, "inside-
out" compared to that of the superior planets. Pretty much exactly as Oriel is
trying to say.

He may not be getting some nuances right, or some of the terminology right, but
here he is just expressing a basic truth. As if it were a new discovery on his
part, rather than something so well known as to be utterly trite... although,
given the reaction to what he is saying here, maybe that impression is less
wrong than I think.

John Savard
  #4  
Old May 16th 18, 08:11 AM posted to sci.astro.amateur
Gerald Kelleher
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Default Illusory loops vs actual loops.

On Tuesday, May 15, 2018 at 9:45:07 PM UTC+1, palsing wrote:


Finally, look for the graphics near the bottom of this page...

http://www.nakedeyeplanets.com/venus...htm#8yearcycle


The phases of Venus dictate its position to the Sun as seen from a slower moving Earth so in effect we see that faster moving planet runs its smaller orbital circuit around our parent star in much the same way we see Jupiter's satellites run around the parent planet -

https://www.youtube.com/watch?v=FcrBAuLBXag

Using this perspective as an anchor insofar as the Sun is always central as we see phase development of the orbit of Venus, the change in the position of the stars to a moving Venus and the stationary Sun becomes the dominant feature as the motion of the Earth creates that change -

https://www.youtube.com/watch?v=MdFrE7hWj0A


The first Sun centered astronomers were chained to the predictive Greek framework where everything, including the Sun, moved through the constellations so that direct/retrograde resolution wasn't partitioned for the faster and slower moving planets seen from Earth -

Kepler
". . . the ancient hypotheses clearly fail to account for certain important matters. For example, they do not comprehend the causes of the numbers, extents and durations of the retrogradations and of their agreeing so well with the position and mean motion of the sun. Copernicus alone gives an explanation to those things that provoke astonishment among other astronomers, thus destroying the source of astonishment, which lies in the ignorance of the causes." 1596, Mysterium Cosmographicum


Whether you approach the insight in simple or complex form, the narrative stands as something new even though the pieces were always there.



  #5  
Old May 16th 18, 01:28 PM posted to sci.astro.amateur
[email protected]
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Default Illusory loops vs actual loops.

On Wednesday, May 16, 2018 at 8:11:34 AM UTC+1, Gerald Kelleher wrote:

The phases of Venus dictate its position to the Sun as seen from a slower moving Earth so in effect we see that faster moving planet runs its smaller orbital circuit around our parent star in much the same way we see Jupiter's satellites run around the parent planet -


To see why this is wrong, look up how long Io takes to orbit Jupiter, and how long it takes to go from left of Jupiter to right and back to left.

Then look up how long Venus takes to orbit the Sun, and how long Venus takes to go from Eastward elongation to Westward and back.

This exercise involves looking at numbers, so Gerald is excused.
  #6  
Old May 16th 18, 06:44 PM posted to sci.astro.amateur
Paul Schlyter[_3_]
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Default Illusory loops vs actual loops.

On Tue, 15 May 2018 21:26:37 -0700 (PDT), Quadibloc
wrote:
Mercury, on the other hand, takes exactly *one* year to make a

complete circle
of the Zodiac, as seen from the Earth - because it never gets very

far from the
Sun as we see it from our vantage point.


The retrograde loops in that one year circle around the Earth...

reflect
Mercury's actual motion around the Sun.


If so, why is the number of retrograde loops of Mercury as seen from
the Earth during one Earth year one less than the number of
revolutions of Mercury around the Sun during the same time period?
  #7  
Old May 16th 18, 06:57 PM posted to sci.astro.amateur
Quadibloc
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Default Illusory loops vs actual loops.

On Wednesday, May 16, 2018 at 11:44:31 AM UTC-6, Paul Schlyter wrote:
On Tue, 15 May 2018 21:26:37 -0700 (PDT), Quadibloc
wrote:
Mercury, on the other hand, takes exactly *one* year to make a

complete circle
of the Zodiac, as seen from the Earth - because it never gets very

far from the
Sun as we see it from our vantage point.


The retrograde loops in that one year circle around the Earth...

reflect
Mercury's actual motion around the Sun.


If so, why is the number of retrograde loops of Mercury as seen from
the Earth during one Earth year one less than the number of
revolutions of Mercury around the Sun during the same time period?


Well, that is one of the nuances. The retrograde loops, if the Sun weren't quite
so bright, could be visually appreciated as our seeing Mercury revolving around
the Sun just as we see Jupiter's moons revolving around it.

But our viewpoint of the Sun keeps changing as we orbit the Sun itself. That
causes the Sun's apparent motion in the sky, and it also changes how we view the
Mercury-Sun system. And, yes, that subtracts one loop. (And ignoring this
particular difference, of course, does belong to the family of misconception
that Oriel is famous for.)

So I suppose you could say that Oriel is wrong because the retrograde loops are
not absolutely pure Mercury motion, devoid of influence from the Earth's motion.
But I see his current remarks on this issue merely as saying what is true: in
the case of an inferior planet, the loops reflect the planet's motion, and the
general outer cycle is due to our orbit - and with a superior planet, it's the
other way around.

That basic fact is true, but, yes, this nuance is definitely something we could
expect him to get wrong. I didn't really see him as getting that far yet.

John Savard
  #8  
Old May 16th 18, 07:02 PM posted to sci.astro.amateur
Quadibloc
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Default Illusory loops vs actual loops.

On Wednesday, May 16, 2018 at 6:28:29 AM UTC-6, wrote:
On Wednesday, May 16, 2018 at 8:11:34 AM UTC+1, Gerald Kelleher wrote:


The phases of Venus dictate its position to the Sun as seen from a slower
moving Earth so in effect we see that faster moving planet runs its smaller
orbital circuit around our parent star in much the same way we see Jupiter's
satellites run around the parent planet -


To see why this is wrong, look up how long Io takes to orbit Jupiter, and how
long it takes to go from left of Jupiter to right and back to left.


Then look up how long Venus takes to orbit the Sun, and how long Venus takes
to go from Eastward elongation to Westward and back.


This exercise involves looking at numbers, so Gerald is excused.


That doesn't make it "wrong", since now you're talking about a nuance which,
while something Oriel certainly would be likely to get wrong, in this case he
hasn't gotten far enough to be even talking about it.

I mean, suppose you are looking at a music box with a rotating statue of a
dancer on it... from a golf cart riding in a circle around the table. Naturally,
the period between times when the dancer faces you is changed because your trip
around the table has to be subtracted from its motion. But does that mean you
aren't actually seeing the dancer's rotation?

John Savard
  #9  
Old May 16th 18, 07:10 PM posted to sci.astro.amateur
Gerald Kelleher
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Default Illusory loops vs actual loops.

Adults should discuss what is in front of them as proof of the Earth's orbital motion along with the fundamentals of timekeeping is tied up with the change in position of the stars relative to the orbital plane and the stationary Sun, at least for the purpose of determining the actual loops of the faster moving Venus and Mercury.

It is why Tycho couldn't accept the reasoning of Copernicus as the stellar background references require two separate treatments, one where the stars don't move for the slower planets as the faster Earth overtakes them -

https://apod.nasa.gov/apod/ap120809.html

The faster moving Venus and Mercury require a separate reference system where the stars change their position to the central Sun (Earth's orbital motion) along with the individual motions of the faster planets. The phases are not so much restrictions as they prevent those planets from any sense of illusory loops.

Give it a go and hammer out the solution acceptable for the wider public.
  #10  
Old May 16th 18, 08:20 PM posted to sci.astro.amateur
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Default Illusory loops vs actual loops.

On Wednesday, May 16, 2018 at 7:10:58 PM UTC+1, Gerald Kelleher wrote:
The phases are not so much restrictions as they prevent those planets from any sense of illusory loops.


But as we keep telling you, gerald, both Venus and Mercury DO execute illusory loops against the background stars, just like the superior planets do. Myself and palsing have both posted links to little web animations of their motions - the sort of thing you usually claim as the very best evidence for you ramblings.
 




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