Buoyant Centre of Dark Matter Is A Focus of Elliptic Orbit of Planet

A spring force explains a negative gravity of the dark matter, and the spring force equals buoyant force, and there is a buoyant center of the dark matter of the solar system which is one focus of the elliptic orbit of the planets (the other focus is the sun). Inertial force is a force of a spacetime structure of the dark matter; and gravity is a force of a massenergy structure of the matter. The equivalence principle is a relationship that the force of a spacetime structure (as the first driving force) equals the force of a massenergy structure A equation of a balanced system between the force of a spacetime structure and the force of a massenergy structure decides the equation of the elliptic orbit of the planets. ``SPACETIME STRUCTURE, MASSENERGY?STRUCTURE, AND EXPLANATION OF HUBBLE'S REDSHIFT, DARK MATTER, AND DARK ENERGY'' \subsubsection{http://meetings.aps.org/Meeting/APR19/Session/G16.9} \label{subsubsec:mylabel1} ``New Einstein Field Equation Explain of Structure of Fluid'' \subsubsection{http://meetings.aps.org/Meeting/APR18/Session/F01.48} \subsubsection{``MEST- there is a dark hole around solar system''} \label{subsubsec:mylabel2} \underline {http://meetings.aps.org/link/BAPS.2015.APR.L1.2}