In the far future(?10?^85years) an "element" called positronium will develop with a diameter of the current observable universe of 93 billion light years. (Remember that light travels at 3×?10?^8 m/s). This element consists of an electron and a positron, both of which have a mass 9.11×?10?^(-31) kgorbiting a common center of mass. The force between them is given by Coulombs law F=(Ke^2)/r^2 , where K=8.99×(?10?^9 Nm^2)/C^2 ,e=1.602×?10?^(-19) C, and r is the distance between the particles. How long does it take for these particles to orbit each other? I.e. what is their orbital period?