### Laplace-Lagrange secular theory

**(Laplace-Lagrange secular evolution theory)**
(theory of evolution of planetary orbits)

**Laplace-Lagrange secular theory**
(or **Laplace-Lagrange secular evolution theory**)
is a theory of the (secular) perturbation of planet orbits
(a perturbation theory)
when two or more astronomical objects are orbiting a third,
that grew from the work of Laplace and Lagrange.
It was developed to investigate whether Newtonian dynamics
is consistent with stable solar system planetary orbits,
i.e., is it consistent with known observation and
with theories of the age and evolution of the solar system.
Today the theory can be compared/validated with long-term computer
orbit simulations.
The theory has naturally gained recent interest for analogous
analysis of orbits of other systems such as binary stars and
systems including extra-solar planets.

(*mathematics,dynamics,orbits,kinematics*)
**Further reading:**

http://farside.ph.utexas.edu/teaching/celestial/Celestialhtml/node91.html

http://phasm-astr27.tripod.com/webonmediacontents/ssd1.pdf

http://www.scholarpedia.org/article/Stability_of_the_solar_system

https://arxiv.org/abs/1209.5996

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