Milankovitch cycles is an intriguing concept with many questions

Milankovitch cycles refer to long-term variations in Earth’s orbit and axial tilt that affect climate patterns over tens of thousands to hundreds of thousands of years. These cycles include:

1. **Eccentricity**: The shape of Earth’s orbit around the Sun, changing from more circular to more elliptical over about 100,000 years.
2. **Obliquity**: The tilt of Earth’s axis, which varies between 22.1° and 24.5° over a period of around 41,000 years.
3. **Precession**: The wobble of Earth’s axis, which causes the positions of the equinoxes to shift over roughly 26,000 years.

These cycles influence the distribution and intensity of sunlight received by Earth, contributing to climate fluctuations like ice ages. Questions often arise around the relative impact of these cycles on climate, how they interact with other factors (like greenhouse gases and ocean currents), and their role in triggering past climate shifts. If you’re interested, I can dive into more specific questions!
How is it even remotely possible that ancient peoples could even consider a 26,000 year cycle?
It’s an excellent question. The 26,000-year precession cycle is far beyond the lifespan or written history of any ancient civilization, so it’s unlikely that they could directly observe it. However, there are a few ways ancient cultures might have noticed long-term patterns that hinted at such cycles:

1. **Observations of the stars**: The precession of Earth’s axis affects the position of the stars over time. For example, the North Star changes over millennia. Ancient peoples may have noticed that certain stars or constellations shifted positions over time, particularly with the rise and fall of civilizations, and linked this to cosmic events or deities.

2. **Astronomical alignments**: Many ancient structures, like the pyramids in Egypt or Stonehenge in England, are aligned with celestial events such as solstices and equinoxes. These alignments could have been observed over generations, and ancient cultures might have recorded changes in these alignments as they passed down knowledge over centuries. While 26,000 years would be too long for a single civilization to track, smaller cycles, like the 1,000-year shift of constellations, could have been passed down in myth or oral traditions.

3. **Myth and cyclical thinking**: Many ancient cultures had cyclical views of time, seeing history as a repeating pattern of ages, cycles, or rebirths. This concept may have been inspired by recurring natural phenomena like seasons, lunar cycles, and even glacial cycles that affected their environment. These mythologies could be symbolic representations of the longer cycles like precession.

While it’s unlikely they had an accurate understanding of a 26,000-year precession cycle in the scientific sense, they may have observed indirect effects over generations and encoded this knowledge in their astronomy, myths, and legends. The idea of vast cycles of time is deeply ingrained in many ancient cultures, even if not tied to the precise mechanism we understand today.