Remember Pioneer 10 and 11?
Both were blasted out into Space in 1972/3 in opposite directions
Both were equipped with a Nuclear power supply, enabling them to send a radio pulse, back to Earth when accessed.
They are still both speeding out of our Galaxy to this day, 35 years later.
Ten years ago in 1997 both Pioneers transmitters were shut down, when the spacecraft were about 134 AU from each other. (One Astronomical Unit equals 93 million miles)
Later, the doppler messages decoded from both Spacecraft indicated that both craft were de-accelerating at the rate of 3000 miles per year, upon year.
That is the mysterious anomaly that has been troubling scientists as to the cause, for many years.
Both spacecrafts speed was expected to remain constant, once they had past the orbit of Pluto, and our Suns gravitational influence.
Did the marked slowing of both Pioneers, mean that local gravity changed towards the edge of our Galaxy?
Or were they encountering the invisible dark matter that supposedly prevents the edges of spinning galaxies from flying off into space?
Were they being affected by a real Michelson Morley effect? That might only be detectable in space, far away from all gravitational effects and Galactic influence?
Might the law of physics be just a little different way out in space than here, in our own neighborhood?
To envisage a Pioneer Spacecraft speeding through another part of the Galaxy, might be difficult enough, for any watching Alien to comprehend. .....It should'nt be there.
Prehaps a metal machine fabricated and built in our 'alien' universe, is not welcome? In that its atomic structure, de-crystalises, or otherwise dis-intergrates, upon entering a universe where physical properties, might be different?
Prehaps Einsteinian time dilation has affected the radio-active materials of its power supply, and the reaction on its other metals?
It seems that the answer is too important to disregard,-as the Planetary Society has just recieved funds to enable them to re-evaluate the 30 years of doppler data tapes that they have on their computers.
Their final answer to the Pioneer Anomaly, might well alter our view of physics, as it exists in other Galactic neighborhoods.
Even rewrite the physical world, as we know it.
http://planetary.org/explore/topics/past_missions/pioneer_10_and_11.htmlhttp://www.planetary.org/programs/projects/pioneer_anomaly/update_200603.html 
