the long cycles of the Dance: the Earth, Moon and Sun.
See Part 1 of Cycles of Life
Continuing our exploration of physical phenomena and longer periods of time, I’m taking a look at the Sun and the Solar System, and their relationship to Earth. Milankovitch cycles, geological time, evolution are also included, up to about the Holocene Epoch.
In the Invisible Landscape Terence & Dennis McKenna use the I Ching to tie the 64 hexagrams to lunations, solar cycles and the precession of the equinoxes as follows:
6 x 64 = 384 days = 13 lunations
(note: 64 hexagrams of 6 lines each is the amount of lines in the entire I Ching)
384 days x 64 = 67 years 104.25 days
= 6 solar cycles (6 x 11.2 solar years)
6 solar cycles x 64 = 4306+ years
= 2 zodiacal ages
6 x 4306+ years = 25, 836 years
= 1 Precession of the Equinoxes
This is a numerological system, and the results are approximate and idealized. However, it’s this kind of symbolic equivalence that I’m hoping to flesh out of theAbysmal Calendar system. Why? It’s all about the stories, my friends.
the Sun – Spottiest Timekeeping System in History
The Sun is our principal time machine, and as such, we’re familiar with its role in the Day, the Lunation and the Year. I won’t belabour those measures here. However, as the hub of the solar system, it is key to the orbit of the planets, which we have tracked for thousands of years. Those figure into timekeeping in many traditions.
The solar cycle of sunspots has only been recorded since about 1755. Solar cycles have a mean duration of about 11 years, with a great deal of variance (from 9 years up to almost 14). At the moment, we’re about midway through solar cycle 24.
One coincidence of note: we began recording solar cycles in 1755, 3 years after the British Empire adopted the Gregorian Calendar, making it the most widespread single calendar in use. Not sure if that means anything, but we could make it mean something. That’s what our brains are for.
Lunar Periods of Note
|from Introducing Biological Rhythms
|Due to the gratiation effect of the Moon since its formation 4.45 billion years ago (bya), the Earth’s day has been slowly becoming larger*
||Duration of one rotation of the earth (h)
|225 my hence
|* As the Moon has slowly moved away from Earth, its effect on the Earth’s day length has also been slowing down. One second is added to our day every 62,500 years.
the Hipparchic Cycle is an eclipse cycle that closely matches integer numbers of several cycles: synodic months (4267), anomalistic months (4573), years (345), and days (126007 + about 1 hour); it is also close to the draconic months (4630.53…)
Keeping this relatively simple, the orbital (sidereal) and synodic periods. These are also changing over longer periods of time, naturally.
||4,332.59 days11.8618 years
||10,759.22 days29.4571 years
||30,799.095 days84.323326 years
||60,190 days164.79 years
There are also annual Meteor showers to mark the year.
Haley’s comet is the ony periodic comet that is clearly visible from Earth, and has a period of 75-76 years.
Milankovitch Cycles – the Earth in Motion
Milutin Milanković calculated aspects of Earth’s motion, notably Precession (precession of the Equinoxes in particular), Nutation and Orbital Forcing (changes to the Earth’s axial tilt and path of its orbit). He determined the relationship of these motions to changes in Earth’s climate.
The tilt of Earth’s axis oscillates between 22.1° and 24.5°. This cycle takes 41,000 years to shift from one extreme to the other and back. It is currently 23.44° and decreasing. It is estimated to reach 22.1° around the year 10,000 CE – 8,000 years from now.
The shape of Earth’s elliptical orbit oscillates between nearly circular (eccentricity of 0.005) and mildly elliptical (eccentricity of 0.058). It is currently 0.017.
The major component of these variations occurs on a period of 413,000 years (eccentricity variation of ±0.012). A number of other terms vary between components 95,000 and 125,000 years (with a beat period 400,000 years), and loosely combine into a 100,000-year cycle.
The more elliptical the orbit, the more variation in the length of seasons, solar radiation and temperatures.
The period of Nutation, the wobble in the course of the axial precession. The major component of the nutation cycle is 18.6 years, which coincides with the precession of the Moon’s orbital nodes.
The precession of the equinoxes proceeds at variable rates, but is commonly rounded up to 26,000 years (25,772 Julian years is the current estimate).
The Apsidal Precession is the rotation of Earth’s orbit around the Sun, causing a shift in the time when Earth is at its closest and furthest from the Sun. This is also expected to shorten the precession of the Equinoxes. This is estimated at 112,000 years. Its effect on the seasons is illustrated above.
Because the anomalistic year is longer than the sidereal year while the tropical year (which calendars attempt to track) is shorter due to the precession of Earth’s rotational axis, the two forms of ‘precession’ add. It takes about 21,000 years for the ellipse to revolve once relative to the vernal equinox, that is, for the perihelion to return to the same date (given a calendar that tracks the seasons perfectly). The dates of perihelion and of aphelion advance each year on this cycle, an average of 1 day every 58 years.
The plane of Earth’s orbit drifts up and down with respect to the invariable plane of the solar system, roughly equivalent to the orbit of Jupiter. This oscillation takes about 100,000 years, which is similar to the eccentricity period as well as the ice age period
As attractive as round numbers are, one cannot discount the 100,000 year problem.
the Earth – Geological Timeline
4.54 billion years ago the Earth is born
4.53 billion years ago – formation of Moon
Graphical Timeline and links
eon >= 500 million years
era >= 100s million years
epoch = 10s millions years
age = millions years
Hadean 4.7 – 3.8 bya
Archaen 3.8 – 2.5 bya
Proterozoic 2.5 bya – 542 mya
Phanerozoic 542 mya – present
Paleozoic 542-251 mya
Mesozoic 250 – 65 mya
Cenozoic 65 mya – present
Paleogene 65 – 23 mya
Neogene 23 – 2.6 mya
Quaternary 2.6 mya – present
Pleistocene 2.6mya – 11,700 years ago
Holocene 11,700 years ago – present
Holocene epoch – you’re living it.
Glaciations & Glacial Ages
Glacial Ages refers to the longer periods in which ice sheets advance over and retreat from the Northern and Southern Hemispheres. During any given age, there are periods of glaciation as the ice advances, and interglacial periods where it retracts, such as the one we’re in now.
There have been five major Glacial Ages
Last glacial period ~13,000 years ago (estimates vary)
Evolution and Mass Extinction Events
The basic timeline of evolution:
- 3.8 billion years of simple cells (prokaryotes),
- 3 billion years of photosynthesis,
- 2 billion years of complex cells (eukaryotes),
- 1 billion years of multicellular life,
- 600 million years of simple animals,
- 570 million years of arthropods (ancestors of insects, arachnids and crustaceans),
- 550 million years of complex animals,
- 500 million years of fish and proto-amphibians,
- 475 million years of land plants,
- 400 million years of insects and seeds,
- 360 million years of amphibians,
- 300 million years of reptiles,
- 200 million years of mammals,
- 150 million years of birds,
- 130 million years of flowers,
- 65 million years since the non-avian dinosaurs died out,
- 2.5 million years since the appearance of the genus Homo,
- 200,000 years of anatomically modern humans,
- 25,000 years since the disappearance of Neanderthal traits from the fossil record.
- 13,000 years since the disappearance of Homo floresiensis from the fossil record.
The largest of greater Extinction Events (EE) is the Permian-Triassic EE which saw the demise of 96% of aquatic species, and 70% of terrestrial. We’ve had a few of these during Earth’s history, and the major events are worth noting.
There are lesser extinction events as well, the most recent of which we are believed to be responsible for.
It has been suggested variously that extinction events occurred periodically, every 26 to 30 million years,or that diversity fluctuates episodically every ~62 million years.
grey denotes all genera; green are well defined genera; the red line is the trend; the yellow arrows are the big five EE; the blue arrows lesser EE
Summary from Part 1:
- 13.7 billion years ago, Universe born
- 13.2 billion years ago, Milky Way born
- 4.56 billion years ago, Sun born
- 225-250 million years – Solar orbit of Sagittarius A* (Galactic Centre)
- 88 million years – oscillation cycle of solar system during galactic orbit
- 1,190 years – Solar system travels 1 light year
- 7 days – Solar system travels 1 AU
- 3-5 billion years hence, the Milky Way will collide and merge with the Andromeda galaxy.
- 10 billion years hence, the Sun dies
- 100 billion to 1 trillion years hence, the galaxies of the local group are expected to merge.
So many numbers, so much meaning, so much meaninglessness. I hope to sift through the data, and come up with some rough estimates of key periods and events to use as anchor points in a calendar system that refers to longer periods of time (epochs, eras, etc…). If this works out by any stretch, it may be something of interest to the Long Now Foundation. Not that they don’t have their work cut out for them already.
310 Days to Dec 21st 2012