1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I New interpretations of the Pioneer effect !?

  1. Apr 20, 2016 #1
    Dear all

    I' d like to draw the attention on (and discuss) something extremely strange i noticed in recent publications related to the Pioneer effect. This does not require more than undergraduate level and its only about very basic classical physics : the Doppler effect and nothing else!

    After the final verdict by Wikipedia:

    "The apparent Pioneer anomaly was a matter of tremendous interest
    for many years, but has been subsequently explained (in 2012) by an anisotropic
    radiation pressure caused by the spacecraft's heat loss" ,

    I noticed with great surprise that J.D. Anderson is not convinced !!

    Anderson from the JPL could be called "Mister Pioneer effect expert" because he was among the first to discover and analyse in details the effect, and he remains the scientist who has published the more articles on the subject, for instance this one :
    http://arxiv.org/abs/gr-qc/0104064, which is the more cited reference on the subject

    But last summer JD Anderson published http://arxiv.org/pdf/1506.08070.pdf, where he tries to explain the pioneer effect as a consequence of a new fundamental physics theory (don't try to understand it , it's not necessary for the following). Not only Anderson is not convinced by the heat loss explanation but he is quite specific :

    "the thermal contribution to the anomaly can be approximately modeled according to a weighted mean of the original analysis of Ref. 2 with the analysis of Ref. 4, giving almost ∼ 12% of the full observed unmodeled ‘acceleration’ value" he says on page 2 of the article, and this is later discussed in more details in the conclusion.

    Then before trying to explain the theory, on page 4 he says : "the analysis in this section is very much inspired by the work of Ref. 44" which establishes the formula number (4) in Anderson paper (corresponding to formula number (96) in Kopeikin article of Ref 44 which is http://arxiv.org/pdf/1207.3873v1.pdf )

    Anybody will recognize the formula as a very basic doppler effect formula plus an extra term presumably responsible for the pioneer effect. Indeed the game is just to compare the received frequency f3 on earth from Pioneer to the emitted frequency f1 from earth toward the Pioneer spacecraft which behaves almost like a mere mirror (actually there is a PLL and a frequency multiplier but this is already taken into account in the comparison of frequencies).

    The formula is : f3/f1 = 1 -2 v/c +2H0 (t2-t1) (A)

    where v is the relative speed, c the speed of light and
    again dont try to understand the origin of the Hubble term (H0) on the right. What we just need to know is that in this formula t2-t1 is just the radiowave propagation time from earth to Pioneer so 2(t2-t1) is merely the round-trip time.

    You might notice that in the Kopeikin paper the formula is f3/f1 = 1 -2 v/c +2H0 (t3-t1) where the anomalous term is twice bigger because t3-t1 ~ 2 (t2-t1) (round trip vs one way). Sir Kopeikin acknowledged this to me (private email) as being a typo corrected in another version of his article he sent to me ... so at this level the correct formula is really according all those authors (A) above .

    Now if you look carefully at equation (A), just as the v/c term for constant speed, the term proportionnal to H0 (constant) and (t2-t1) (constant because the speed of the spacecraft is assumed negligible for this term: i.e. the anomalous Hubble term would be there even if the spacecraft was at rest) is thus constant in time !

    This means that this term could not in anyway be subsequently interpreted as an effective spacecraft acceleration term! At the contrary it could be interpreted as a constant Doppler anomalous extra term , e.g mimicking additionnal constant speed.

    Yet it has always been reported that the Pioneer anomaly can be interpreted as an unmodeled unexpected acceleration! So here, if i did not miss something basic, we have an incredible mistake made by an expert in general relativity (Kopeikin) and propagated by Anderson and Feldman (solar system physics and GR experts), and published in Phys Rev one of the most famous journal. All those highly respected theorists are seemingly just making this incredible confusion between speed and acceleration !

    So the sentence after the formula in Anderson article : "which would give the desired blueshift to possibly explain the anomalous acceleration in frequency shift seen with the Pioneer spacecrafts once we integrate over multiple round-trip cycles" is obviously incredibly wrong , as is the Kopeikin reasoning between equations (96) and (103):
    Indeed the integrated drift over many up/down link bouncing cycles would never have been interpreted as an acceleration !! And the time derivative of the integrated effect has nothing to do with an acceleration !

    I find this so incredible that i would appreciate feedback and comments from other physicists here because i dont want to email Kopeikin again and make a fool of myself if i missed something very basic !!

    thank you in advance!

    Last edited: Apr 20, 2016
  2. jcsd
  3. Apr 20, 2016 #2
    A formula that could be interpreted as an acceleration is the following

    f3/f1 = 1 -2 v/c +2H0 t

    where t = (t1+t3)/2

    and one does not need to "integrate over many round trips" but just plot f3-f1 or f3/f1 as a function of t
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted