I have read a book claiming that the speed of the Voyager probes do not fit neither the Newton's laws of motion nor Einstein's relativity theory. Is it a recognized scientific fact? Where can I find the relevant information?

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    $\begingroup$ I think you might be thinking of the Pioneer anomaly, not Voyager. That was accounted for by radiation pressure from waste heat. $\endgroup$ – DylanSp Feb 19 '16 at 12:52
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    $\begingroup$ I agree with DylanSp that you are probably thinking of Pioneer rather than Voyager, but I have edited the title of your question to hopefully more accurately summarize the content of the question. You may want to edit further to at least indicate which book you have read that states this, and how it is stated in that book. $\endgroup$ – a CVn Feb 19 '16 at 13:22
  • $\begingroup$ Neither Newton nor Einstein's theories are sufficient on Earth, as they fail to predict friction. Now there's of course no planetary atmosphere in space, but it's not a perfect vacuum either. How much friction does that cause? How much trust is there from solar radiation? All those are inputs to the laws of motions, not predictions from the laws of motion. $\endgroup$ – MSalters Feb 22 '16 at 15:31
  • $\begingroup$ @MSalters: you are confusing several things. It is correct that they don't predict friction, but this is the right thing to do. They give general formula of mechanics. Friction is one of force (or acceleration) that one should account when using Newton or Einstein equations. Then there is the predict part. Without measurements it is difficult to estimate the quantity of friction (chicken-egg problem when we have only few probes). $\endgroup$ – Giacomo Catenazzi Feb 28 '16 at 10:11
  • $\begingroup$ Actually, they both account for friction just fine on microscopic level. It's just that friction being an effect of trillions of interactions per square millimeter of affected surface, the solution scales up badly, being still perfectly correct but completely impractical to solve, requiring far more calculations than anyone would be willing to undertake. $\endgroup$ – SF. Apr 30 '16 at 12:12

Wikipedia article "Pioneer anomaly" seems to address this. The accepted answer to this slowing down of the spacecraft slightly more than predicted is that the deceleration was caused by "an anisotropic radiation pressure caused by the spacecraft's heat loss."

So the anomaly was caused by radiation pressure caused by heat being emitted from the spacecraft.

The is also an article here at Nature Physics

  • $\begingroup$ Excellent answer and link! I was happy to see that the actual PDF is available and not behind a paywall. A version of the actual Physical Review Letter article cited there can also be viewed via ArXiv $\endgroup$ – uhoh Apr 30 '16 at 12:24
  • $\begingroup$ I've asked a related question. $\endgroup$ – uhoh Apr 30 '16 at 13:06

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