A restoration in the time-symmetric theory and associated new results
  The concept of absorption of a photon moving backwards in time is reexamined, and it is found that its interpretation as absorption is wrong, its original interpretation rather as an emission being restored. The result is that the anticosmos is invisible rather than indistinguishable from the cosmos, and as such it is qualitatevely a candidate for constituting the dark matter. Newton&#180;s law of gravitation is then generalized to refer either to matter (of the cosmos) and/or antimatter (of the anticosmos), and quantitatevely is found for the anticosmos to constitute the dark matter, as being (absolutely) equal in ammount of antimatter to the ammount of matter in the cosmos.Finally, a mechanism of gravitational repulsion from antimatter is proposed to explain the observed deceleration of Pioneer 10 and Pioneer 11, and an analytical way is exposed to calculate the position, as well as its (anti-)mass, of the responsible anti-body. 
Evangelos Chaliasos