Changes

* The anomalous acceleration could be due to the spacecraft venting energy in certain directions.<ref>http://www.symmetrymagazine.org/breaking/2008/04/13/pioneer-spacecraft-a-step-closer-to-being-boring/</ref>.  However, such effects would be expected to be more significant earlier on, when the power sources were less degraded<ref name="Nieto" />.  The opposite was actually the case.

* The anomalous acceleration could be due to the spacecraft venting energy in certain directions.<ref>http://www.symmetrymagazine.org/breaking/2008/04/13/pioneer-spacecraft-a-step-closer-to-being-boring/</ref>.  However, such effects would be expected to be more significant earlier on, when the power sources were less degraded<ref name="Nieto" />.  The opposite was actually the case.

* The theory of [[General Relativity]] and the [[Law of Universal Gravitation]] could be wrong; the gravitational force could be slightly stronger than predicted.  In this context, it is important to note that other spacecraft flying in hyperbolic trajectories around celestial bodies have also experienced anomalous gravitational effects.

* The theory of [[General Relativity]] and the [[Law of Universal Gravitation]] could be wrong; the gravitational force could be slightly stronger than predicted.  In this context, it is important to note that other spacecraft flying in hyperbolic trajectories around celestial bodies have also experienced anomalous gravitational effects.

* There could be gravitational forces from other celestial bodies that have not been taken into account.  Dr. [[Russell Humphreys]] has explained<ref name="Humphreys">Russell Humphreys.  "[http://creation.com/images/journal_of_creation/vol21/5181creationist.pdf Creationist cosmologies explain the anomalous acceleration of Pioneer spacecraft]."  ''Journal of Creation'', August 2007.</ref> the Pioneer Anomaly as part of [[Starlight_problem#Humphreys.27_model|his new cosmology]], as the pull from the center of mass of the universe, which he locates inside the [[solar system]].  However, he does not explain why this gravitational force does not influence the motion of the planets.

* There could be gravitational forces from other celestial bodies that have not been taken into account.  Dr. [[Russell Humphreys]] has explained<ref name="Humphreys">Russell Humphreys.  "[http://creation.com/images/journal_of_creation/vol21/5181creationist.pdf Creationist cosmologies explain the anomalous acceleration of Pioneer spacecraft]."  ''Journal of Creation'', August 2007.</ref> the Pioneer Anomaly as part of [[Starlight_problem#Humphreys.27_model|his new cosmology]], as the pull from the center of mass of the universe, which he locates inside the [[solar system]].  However, he does not explain why this gravitational force does not influence the motion of the planets.