• Question: what is the explanation of pioneer anomaly?

    Asked by maxsmith1 to Arttu, Ceri, James_M, Monica, Philip on 16 Jun 2011.
    • Photo: James M Monk

      James M Monk answered on 13 Jun 2011:

      The Pioneer anomaly is a small acceleration of the Pioneer space craft towards the Sun that cannot be explained by Newtonian gravity. Since gravity is not that well tested on scales of the size of the Solar System, it was suggested that this anomalous acceleration is an indication of a modification to Newtonian gravity.

      The simplest explanation is that Pioneer is not a controlled experiment that was designed to test gravity. We do not know the exact condition of the space craft and there is not a control craft under similar conditions close to Earth for ~40 years. One could easily imagine there are leaks from the space craft or other similar effects causing a small acceleration.

      I believe that the Pioneer anomaly remains unsolved, although I would strongly suspect it will turn out to be the simpler explanation, rather than a modification to Newtonian gravity.

    • Photo: Arttu Rajantie

      Arttu Rajantie answered on 16 Jun 2011:

      The Pioneer anomaly is really intriguing, but unfortunately it is looking increasingly likely that the anomalous acceleration is caused by thermal radiation coming from its electrical components.

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