Science and technology is the motive force to promote the development of era.
$$ \frac{{{{\rm{d}}^2}{\bf{x}}}}{{{\rm{d}}{t^2}}} = - G\int {{{\rm{d}}^3}{\bf{x}}'\frac{{{\bf{x}} - {\bf{x}}'}}{{\left| {{\bf{x}} - {\bf{x}}'} \right|}}\rho \left( {{\bf{x}}'} \right)} + {{\bf{F}}_\varepsilon } $$