The Milankovitch Rhythms

Plate 93 speaks for itself: “Ice ages keep time with Earth's orbit.”

The Physics

Slow changes in Earth's tilt, the timing of its seasons and the shape of its orbit alter where sunlight falls. Ice-age cycles in climate records match these rhythms.

periods ≈ 41, 23, 100 kyr

• 41 kyr: obliquity cycle
• 23 kyr: precession cycle (about 19–23 kyr)
• 100 kyr: eccentricity cycle
• 1 kyr: 1000 years

Obliquity: 22.1°–24.5° over ~41 kyr. Now 23.44°. Eccentricity: ~100 kyr and ~405 kyr.

Sources

• J. D. Hays, J. Imbrie, N. J. Shackleton, Science 194, 1121 (1976).
• J. Laskar et al., Astron. Astrophys. 428, 261 (2004).

On the poster

Plate 093, “The Milankovitch Rhythms”: the pixel-art plate with its slogan “Ice ages keep time with Earth's orbit.”, the key equation and the facts panel shown above. Pixelated Physics. Physics. Personified.