Plot of Earth's Precession Cycle

[SwampeastMike]

I post in "Pseudoscience and Speculations", since if the answer to my question is "no", then my speculations become wild.

 

My question:

 

Are we positive that the 26 myr precessionary cycle plots as a circle and not half of a 52 myr figure eight?

 

Should it be a figure eight, "up" has become "down" from at least one perspective and the wild speculation about how far this goes begins.

 

Thank you for your consideration.

[Sisyphus]

It's a 26 thousand year cycle, not 26 million. The gravitational influences which cause the precession are well understood and precisely calculated (though not by me), and those calculations completely agree with observation. So I guess, what would lead you to speculate that these calculations are wrong, and what mechanism could cause a figure eight precession? Also, what do you mean by up becoming down?

 

For reference:

http://en.wikipedia.org/wiki/Precession_(astronomy)

[SwampeastMike]

Thank you for the reply and I do know it's about 26 thousand. I used printers and others shorthand for 1,000, m.

 

I reasonably understand the forces involved in precession. Perhaps it is the constant analogy to a spinning top that bothers me as the earth is nearly spherical yet flattened at the poles; not the least bit pointy like a top. The only way I can imagine it "top like" is via the magnetic field which I can visualize as two tops spinning point-to-point in opposite directions

 

Either way, when I attempt to visualize in my mind and via animations, I see how easily the precessionary cycle could become a figure eight when the cycle finds a point that it can only move by, not through. Have we observed any planet through two regular circular cycles of Earth-like precession? Venus wobbles and Mercury poses space-time questions if my research is correct.

 

You asked, "What do you mean by up being down?"

 

Do please understand that I qualified that statement by saying it required an observation reference that given the time involved can only be called "special".

 

I won't engage in a "prove me wrong" fallacy, but I do ask if anything that has been observed with reasonable verification would preclude a figure-eight plot of precession? Do we have any historic record of when the sun last reversed direction in precession of the solstices?

[insane_alien]

Thank you for the reply and I do know it's about 26 thousand. I used printers and others shorthand for 1,000, m.

 

please, do not use non-scientific prefixes in a science forum it will only cause misunderstandings and confusion.

 

k (for kilo) is the SI prefix for 1000 and would be the preffered one

m as a prefix in SI would be milli or thousandth

M (mega) is million

[mooeypoo]

To your question are we sure about the precession of the Earth, the answer is yes, we're sure. As Sisyphus pointed out, this can be calculated very accurately, and we know the forces that are applied to create this motion.

 

Furthermore, a "figure eight" motion is not very logical -- it means a changing direction, and that would require different types of forces that are applied to achieve the precession to begin with.

 

You should really read the wikipage Sisyphus posted (the link was half broken, notice that there should be a ")" sign at the end of the link): http://en.wikipedia.org/wiki/Precession_(astronomy) It's a good place to start.

[SwampeastMike]

a "figure eight" motion is not very logical -- it means a changing direction

 

Thank you for the suggestion of where to study even though I had already been there other places as well.

 

http://www.crystalinks.com/precession.html

 

The following refers to the top illustration in the link:

 

Imagine that a simlar path is plotted at the south pole as well as the north. Such extends from the opposite side of the axis and by this perspective would appear shifted in horizontal position from the north pole path above.

 

Were precession of the equinoxes the only cycle of motion, I agree completely that a figure eight pattern would not only be illogical but impossible to reasonably imagine because of that 'change in direction'.

 

As the precession occurs in the illustration, the axis will appear perpendicular twice in each cycle with the north and south pole plots in perfect vertical alignment.

 

Now, given the other motions of the earth, I ask:

 

Can the rotational axis of the earth be a vertical tangent to the surface of the sun via a line drawn through both of their centers? If so, then to an observer at the center of the sun, the illustration would have the north and south pole plots in perfect vertical juxtaposition.

 

From that perspective, there is no 'change of direction' to produce a figure eight if the observer at the center of the sun has been turned upside down by a magnetic shift--the precessionary plot would continue to be a circle. Yet from the original "north is up" perspective of the observer, the plot would appear to be a figure eight.

 

My previous research suggested to me that this sort of perspective shift might be related to the space-time problems posed by the precession of Mercury. What happens when gears shift in half an instant? Does north become south?

[stereologist]

If you take a look at a plot of the precession you will notice that the circle crosses by a star called Thuban. I always wondered why an insignificant star had a name. That star would have been the north star about 4800 years ago.

[SwampeastMike]

why an insignificant star had a name. That star would have been the north star about 4800 years ago

 

Exactly. The horizon shifts daily as the earth turns on its tilted axis and wobbles every 13,000 years when viewed only on the solstices.

 

4800 years ago, unfortunately, is not even a quarter of the full 26,000 year precessionary cycle, so by all understanding Thuban had to be the "north star" then.

 

Precession is the very root of "astrology" as we commonly know the term today. I saw it in surviving ceilings of ancient Egypt. Better than in a planetarium, I saw how the horizon viewed in glimpses at the solstices progressed through the twelve signs.