If you look up the pioneer anomaly you will find out that over vast distances they are slightly off in there mesurements on where the probes should be, in that they lose 5,000 meters a year. This means they are going slower than physics says they should. While I am not a physicist (I would like to be) I think this anomaly is not breaking the laws of physics as they claim or having to change laws about gravity. Now they say they are moving slower than expected now this can make sense if they are not accounting for the relativity of time. The faster you go the slower you seem to age... or possibly even move. Now while this is unnoticable on earth, when you are dealing with something that is going in one path for years at a time at high velocities it could impact the speed of which the object (pioneer probes) are moving. The same as a watch A quote from wikipedia on this affect, although in reverse where the gravitational change was greater than the velocital change. Hafele and Keating, in 1971, flew caesium atomic clocks east and west around the Earth in commercial airliners, to compare the elapsed time against that of a clock that remained at the US Naval Observatory. Two opposite effects came into play. The clocks were expected to age more quickly (show a larger elapsed time) than the reference clock, since they were in a higher (weaker) gravitational potential for most of the trip (c.f. Pound, Rebka). But also, contrastingly, the moving clocks were expected to age more slowly because of the speed of their travel. The gravitational effect was the larger, and the clocks suffered a net gain in elapsed time. To within experimental error, the net gain was consistent with the difference between the predicted gravitational gain and the predicted velocity time loss. In 2005, the National Physical Laboratory in the United Kingdom reported their limited replication of this experiment. The NPL experiment differed from the original in that the caesium clocks were sent on a shorter trip (London–Washington D.C. return), but the clocks were more accurate. The reported results are within 4% of the predictions of relativity. Now with this in mind you have to realize that even if this doesnt seem to affect it enough think about this. What happens if you launch a plane from a faster plane the plane that is launched will start slowing down due to friction (which there is little of in space) could that be part of it. If I am wrong I understand but please try to explain in simple terms why i am wrong.