Encyclopedia of geology, five volume set, volume 1 5 (encyclopedia of geology series) ( PDFDrive ) 458

EARTH/Orbital Variation (Including Milankovitch Cycles) 419

Figure 11 (Top) Evolutionary spectrum (frequency vs age, amplitude colour coded) of Ocean Drilling Program Leg 154 lithological
data (combined magnetic susceptibility and colour reflectance) (cf. Figure 10). These data, analysed by Shackleton and colleagues
in 1999, and contrasted to astronomical calculations of Earth’s orbital variations, demonstrate that the geological data contain an
imprint of long term amplitude modulations of astronomical forcing components. (Bottom) The astronomical solution provided
by J Laskar.

geological time-scales. Laskar found that the calculations of orbits diverge exponentially with time for a
given set of initial conditions. This implies, for
example, that if the present position of a planet is
known with a relative error of $10 10, this error

increases to $10 9 after 10 My, and reaches the
order of 1 after 100 My. Despite these limitations,
the determination of astronomical parameters, such
as the planetary masses, velocities, and positions, is
improving due to additional satellite measurements.