PLANETARY MOTION WAS KNOWN WAY BEFORE GALILEO GOT SPANKED BY THE CHURCH FOR CLAIMING THE EARTH CYCLES AROUND THE SUN AND NOT THE OTHER WAY AROUND... MUCH OF WHAT WAS KNOWN ABOUT THE SOLAR SYSTEM HAD BEEN HIDDEN FROM VIEW — AND STILL IS, BECAUSE IT IS INCONVENIENT TO KNOW... 

SOME KNOWLEDGE IS HIDDEN BY FOSSIL FUEL INDUSTRIES, FOXNEWS AND INGNORAMUSES — OR IS BADLY USED BY A FEW DISINGENUOUS PSEUDO-SCIENTISTS — TO PREVENT OUR UNDERSTANDING OF THE PRESENT GLOBAL WARMING.

Plato (c. 360 BC) used the term "perfect year" to describe the return of the celestial bodies (planets) and the diurnal rotation of the fixed stars (circle of the Same) to their original positions; there is no evidence he had any knowledge of axial precession.[5] The cycle which Plato describes is one of planetary and astral conjunction, which can be postulated without any awareness of axial precession.

Hipparchus (c. 120 BC) is the first Greek credited with discovering axial precession roughly two hundred years after Plato's death.

Cicero (1st century BC) followed Plato in defining the Great Year as a combination of solar, lunar and planetary cycles.[6][7]

Plato's description of the perfect year is found in his dialogue Timaeus: 

And so people are all but ignorant of the fact that time really is the wanderings of these bodies, bewilderingly numerous as they are and astonishingly variegated. It is none the less possible, however, to discern that the perfect number of time brings to completion the perfect year at that moment when the relative speeds of all eight periods have been completed together and, measured by the circle of the Same that moves uniformly, have achieved their consummation."[8]

In De Natura Deorum, Cicero wrote

On the diverse motions of the planets the mathematicians have based what they call the Great Year, "which is completed when the sun, moon and five planets having all finished their courses have returned to the same positions relative to one another. The length of this period is hotly debated, but it must necessarily be a fixed and definite time."[6]

Macrobius (early fifth century AD) in his commentary on Cicero's Somnium Scipionis states that 'the philosophers' reckon the Great Year as 15,000 years.[9]

Censorinus (3rd century AD) wrote that Aristarchus of Samos reckoned a Great Year as 2,484 years: but it has been argued that this is a miscopying of 2434, which represents 45 Exeligmos cycles.[9][10]

The origin of the Platonic Year would seem to have no connection with the precession of the equinoxes as this was unknown in Plato's time.[11] Two centuries after Plato, Hipparchus is credited with discovering the period of  equinox precession,[12] and the term "Great Year" eventually came to be applied to the period of that precession caused by the slow gyration of the Earth's axis.

Some time around the middle of the second century BC, the astronomer Hipparchus discovered that the fixed stars as a whole gradually shifted their position in relation to the annually determined locations of the Sun at the equinoxes and solstices... Otto Neugebauer argued that Hipparchus in fact believed that this [36,000 years] was the maximum figure and that he also computed the true rate of one complete precession cycle at just under 26,000 years...[13]

A confusion between the two definitions of the Great Year is believed to have originated with the astronomer Ptolemy (c. 170 AD), who adopted the larger, incorrect figure of 36,000 years. This led to the increasing conflation of the Platonic Great Year—based on planetary cycles—with the precessional Great Year, defined by the movement of the stars.[14] Some scholars have even accused Ptolemy of scientific fraud, suggesting that he may have fabricated observations to support the 36,000-year cycle, despite having access to data that could have led him much closer to the correct figure of 26,000 years.[15]

Josephus (first century AD) refers to a 'Great Year' (Ancient Greek: μέγας ἐνιαυτός) of 600 years.[16]

God afforded them a longer time of life on account of their virtue, and the good use they made of it in astronomical and geometrical discoveries, which would not have afforded the time of foretelling [the periods of the stars] unless they had lived six hundred years; for the great year is completed in that interval.[16]

It has been suggested that he obtained this value from Berossos (c. 3rd century BC) who reckoned time in intervals of 60, 600 and 3600 years.[17]

Isaac Newton (1642 – 1726/27) determined the cause of precession and established the rate of precession at 1 degree per 72 years, very close to the best value measured today, thus demonstrating the magnitude of the error in the earlier value of 1 degree per century.[18]

https://en.wikipedia.org/wiki/Great_Year?

ENTERS MILANKOVITCH:

Small cyclical variations in the shape of Earth's orbit, its wobble and the angle its axis is tilted play key roles in influencing Earth's climate over timespans of tens of thousands to hundreds of thousands of years.

Our lives literally revolve around cycles: series of events that are repeated regularly in the same order. There are hundreds of different types of cycles in our world and in the universe. Some are natural, such as the change of the seasons, annual animal migrations or the circadian rhythms that govern our sleep patterns. Others are human-produced, like growing and harvesting crops, musical rhythms or economic cycles.

Cycles also play key roles in Earth’s short-term weather and long-term climate. A century ago, Serbian scientist Milutin Milankovitch hypothesized the long-term, collective effects of changes in Earth’s position relative to the Sun are a strong driver of Earth’s long-term climate, and are responsible for triggering the beginning and end of glaciation periods (Ice Ages).

Specifically, he examined how variations in three types of Earth orbital movements affect how much solar radiation (known as insolation) reaches the top of Earth’s atmosphere as well as where the insolation reaches. These cyclical orbital movements, which became known as the Milankovitch cycles, cause variations of up to 25 percent in the amount of incoming insolation at Earth’s mid-latitudes (the areas of our planet located between about 30 and 60 degrees north and south of the equator).

The Milankovitch cycles include:

1. The shape of Earth’s orbit, known as eccentricity;
2. The angle Earth’s axis is tilted with respect to Earth’s orbital plane, known as obliquity; and
3. The direction Earth’s axis of rotation is pointed, known as precession.

Eccentricity – Earth’s annual pilgrimage around the Sun isn’t perfectly circular, but it’s pretty close. Over time, the pull of gravity from our solar system’s two largest gas giant planets, Jupiter and Saturn, causes the shape of Earth’s orbit to vary from nearly circular to slightly elliptical. Eccentricity measures how much the shape of Earth’s orbit departs from a perfect circle. These variations affect the distance between Earth and the Sun.

Eccentricity is the reason why our seasons are slightly different lengths, with summers in the Northern Hemisphere currently about 4.5 days longer than winters, and springs about three days longer than autumns. As eccentricity decreases, the length of our seasons gradually evens out.

The difference in the distance between Earth’s closest approach to the Sun (known as perihelion), which occurs on or about January 3 each year, and its farthest departure from the Sun (known as aphelion) on or about July 4, is currently about 5.1 million kilometers (about 3.2 million miles), a variation of 3.4 percent. That means each January, about 6.8 percent more incoming solar radiation reaches Earth than it does each July.

When Earth’s orbit is at its most elliptic, about 23 percent more incoming solar radiation reaches Earth at our planet’s closest approach to the Sun each year than does at its farthest departure from the Sun. Currently, Earth’s eccentricity is very slowly decreasing and is approaching its least elliptic (most circular), in a cycle that spans about 100,000 years. 

The total change in global annual insolation due to the eccentricity cycle is very small. Because variations in Earth’s eccentricity are fairly small, they’re a relatively minor factor in annual seasonal climate variations.

Obliquity – The angle Earth’s axis of rotation is tilted as it travels around the Sun is known as obliquity. Obliquity is why Earth has seasons. Over the last million years, it has varied between 22.1 and 24.5 degrees with respect to Earth’s orbital plane. The greater Earth’s axial tilt angle, the more extreme our seasons are, as each hemisphere receives more solar radiation during its summer, when the hemisphere is tilted toward the Sun, and less during winter, when it is tilted away. Larger tilt angles favor periods of deglaciation (the melting and retreat of glaciers and ice sheets). These effects aren’t uniform globally -- higher latitudes receive a larger change in total solar radiation than areas closer to the equator.

Earth’s axis is currently tilted 23.4 degrees, or about half way between its extremes, and this angle is very slowly decreasing in a cycle that spans about 41,000 years. It was last at its maximum tilt about 10,000 years ago and will reach its minimum tilt about 10,000 years from now. As obliquity decreases, it gradually helps make our seasons milder, resulting in increasingly warmer winters, and cooler summers that gradually, over time, allow snow and ice at high latitudes to build up into large ice sheets. As ice cover increases, it reflects more of the Sun’s energy back into space, promoting even further cooling.

Precession – As Earth rotates, it wobbles slightly upon its rotational axis, like a slightly off-center spinning toy top. This wobble is due to tidal forces caused by the gravitational influences of the Sun and Moon that cause Earth to bulge at the equator, affecting its rotation. The trend in the direction of this wobble relative to the fixed positions of stars is known as axial precession. The cycle of axial precession spans about 25,771.5 years.

Axial precession makes seasonal contrasts more extreme in one hemisphere and less extreme in the other. Currently perihelion occurs during winter in the Northern Hemisphere and in summer in the Southern Hemisphere. This makes Southern Hemisphere summers hotter and moderates Northern Hemisphere seasonal variations. But in about 13,000 years, axial precession will cause these conditions to flip, with the Northern Hemisphere seeing more extremes in solar radiation and the Southern Hemisphere experiencing more moderate seasonal variations.

Precession does affect seasonal timing relative to Earth's closest/farthest points around the Sun. However, the modern calendar system ties itself to the seasons, and so, for example, the Northern Hemisphere winter will never occur in July. Today Earth’s North Stars are Polaris and Polaris Australis, but a couple of thousand years ago, they were Kochab and Pherkad.

There’s also apsidal precession. Not only does Earth wobble on its rotational axis, but Earth’s entire orbital ellipse – that is, the oval-shaped path Earth follows in its orbit around the Sun — also wobbles irregularly, primarily due to its interactions with Jupiter and Saturn. The cycle of apsidal precession spans about 112,000 years. Apsidal precession changes the orientation of Earth’s orbit relative to the ecliptic plane.

The combined effects of axial and apsidal precession result in an overall precession cycle spanning about 23,000 years on average.

A Climate Time Machine 

The small changes set in motion by Milankovitch cycles operate separately and together to influence Earth’s climate over very long timespans, leading to larger changes in our climate over tens of thousands to hundreds of thousands of years. Milankovitch combined the cycles to create a comprehensive mathematical model for calculating differences in solar radiation at various Earth latitudes along with corresponding surface temperatures. The model is sort of like a climate time machine: it can be run backward and forward to examine past and future climate conditions.

Milankovitch assumed changes in radiation at some latitudes and in some seasons are more important than others to the growth and retreat of ice sheets. In addition, it was his belief that obliquity was the most important of the three cycles for climate, because it affects the amount of insolation in Earth’s northern high-latitude regions during summer (the relative role of precession versus obliquity is still a matter of scientific study).

He calculated that Ice Ages occur approximately every 41,000 years. Subsequent research confirms that they did occur at 41,000-year intervals between one and three million years ago. But about 800,000 years ago, the cycle of Ice Ages lengthened to 100,000 years, matching Earth’s eccentricity cycle. While various theories have been proposed to explain this transition, scientists do not yet have a clear answer.

Milankovitch’s work was supported by other researchers of his time, and he authored numerous publications on his hypothesis. But it wasn’t until about 10 years after his death in 1958 that the global science community began to take serious notice of his theory. In 1976, a study in the journal Science by Hays et al. using deep-sea sediment cores found that Milankovitch cycles correspond with periods of major climate change over the past 450,000 years, with Ice Ages occurring when Earth was undergoing different stages of orbital variation.

Several other projects and studies have also upheld the validity of Milankovitch’s work, including research using data from ice cores in Greenland and Antarctica that has provided strong evidence of Milankovitch cycles going back many hundreds of thousands of years. In addition, his work has been embraced by the National Research Council of the U.S. National Academy of Sciences.

Scientific research to better understand the mechanisms that cause changes in Earth’s rotation and how specifically Milankovitch cycles combine to affect climate is ongoing. But the theory that they drive the timing of glacial-interglacial cycles is well accepted.

https://science.nasa.gov/science-research/earth-science/milankovitch-orbital-cycles-and-their-role-in-earths-climate

BUT:

But Milankovitch cycles can’t explain all climate change that’s occurred over the past 2.5 million years or so. And more importantly, they cannot account for the current period of rapid warming Earth has experienced since the pre-Industrial period (the period between 1850 and 1900), and particularly since the mid-20th century.

Scientists are confident Earth’s recent warming is primarily due to human activities — specifically, the direct input of carbon dioxide into Earth’s atmosphere from burning fossil fuels. 

So how do we know Milankovitch cycles aren’t to blame?

First, Milankovitch cycles operate on long time scales, ranging from tens of thousands to hundreds of thousands of years. In contrast, Earth’s current warming has taken place over time scales of decades to centuries. Over the last 150 years, Milankovitch cycles have not changed the amount of solar energy absorbed by Earth very much. In fact, NASA satellite observations show that over the last 40 years, solar radiation has actually decreased somewhat.

Second, Milankovitch cycles are just one factor that may contribute to climate change, both past and present. Even for Ice Age cycles, changes in the extent of ice sheets and atmospheric carbon dioxide have played important roles in driving the degree of temperature fluctuations over the last several million years.

The extent of ice sheets, for example, affects how much of the Sun’s incoming energy is reflected back to space, and in turn, Earth’s temperature.

Then there’s carbon dioxide [AND OTHER WARMING GASES: NOx AND METHANE]. During past glacial cycles, the concentration of carbon dioxide in our atmosphere fluctuated from about 180 parts per million (ppm) to 280 ppm as part of Milankovitch cycle-driven changes to Earth’s climate. These fluctuations provided an important feedback to the total change in Earth’s climate that took place during those cycles.

Today, however, it’s the direct input of carbon dioxide into the atmosphere from burning fossil fuels that’s responsible for changing Earth’s atmospheric composition over the last century, rather than climate feedbacks from the ocean or land caused by Milankovitch cycles.

Since the beginning of the Industrial Age, the concentration of carbon dioxide in Earth’s atmosphere has increased 50 percent, from about 280 ppm to 412 ppm (update: 421 ppm in 2023).

Scientists know with a high degree of certainty this carbon dioxide is primarily due to human activities because carbon produced by burning fossil fuels leaves a distinct “fingerprint” that instruments can measure. Since 1850, Earth’s global average temperature has increased by over 1 degree Celsius (1.8 degrees Fahrenheit). Furthermore, recent scientific assessments show that Earth is expected to warm another half a degree Celsius (almost a degree Fahrenheit) as soon as 2030.

This relatively rapid warming of our climate due to human activities is happening in addition to the very slow changes to climate caused by Milankovitch cycles. Climate models indicate any forcing of Earth’s climate due to Milankovitch cycles is overwhelmed when human activities cause the concentration of carbon dioxide in Earth’s atmosphere to exceed about 350 ppm.

Scientists know of no natural changes to the equilibrium between the amount of solar radiation absorbed by Earth and the amount of energy radiated back to space that can account for such a rapid period of global warming. The amount of incoming solar radiation has increased only slightly over the past century and is therefore not a driver of Earth’s current climate warming.

Since 1750, the warming driven by greenhouse gases coming from the human burning of fossil fuels is over 50 times greater than the slight extra warming coming from the Sun itself over that same time interval. If Earth’s current warming was due to the Sun, scientists say we should expect temperatures in both the lower atmosphere (troposphere) and the next layer of the atmosphere, the stratosphere, to warm. Instead, observations from balloons and satellites show Earth’s surface and lower atmosphere have warmed but the stratosphere has cooled.

Finally, Earth is currently in an interglacial period (a period of milder climate between Ice Ages). If there were no human influences on climate, scientists say Earth’s current orbital positions within the Milankovitch cycles predict our planet should be cooling, not warming, continuing a long-term cooling trend that began 6,000 years ago. 

There’s nothing cool about that.

https://science.nasa.gov/science-research/earth-science/why-milankovitch-orbital-cycles-cant-explain-earths-current-warming/

==============================

SEE ALSO: https://www.youtube.com/watch?v=FS3Jn8lP0ss&t=6s

=======================

SEE ALSO: https://www.theamericanconservative.com/the-secret-weapon-for-energy-dominance-nuclear-waste/

AND HERE COMES A CONUNDRUM.... WHY PREVENT IRAN TO DEVELOP ITS NUCLEAR ENERGY? NOTHING TO DO WITH THEM DEVELOPING NUCLEAR BOMBS... ALL TO DO WITH RETAINING EXCLUSIVITY OF PROCESSES...

NUCLEAR WASTE IS WASTE AND A MAJOR PROBLEM — POSSIBLY FAR MORE PROBLEMATIC THAN GLOBAL WARMING... 

==========================

YOURDEMOCRACY.NET RECORDS HISTORY AS IT SHOULD BE — NOT AS THE WESTERN MEDIA WRONGLY REPORTS IT.

         Gus Leonisky

         POLITICAL CARTOONIST SINCE 1951.

-----------------------

SEE ALSO: https://yourdemocracy.net/drupal/node/33287