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Flaw in creationist solution to the Pioneer anomaly?

Published: 11 May 2013 (GMT+10)

In 2008, Creationist physicist and cosmologist Dr Russ Humphreys published a solution to the Pioneer anomaly in Journal of Creation (see The ‘Pioneer anomaly’ for a general introduction). The Pioneer anomaly is a small but strange deceleration of four outgoing spacecraft: Galileo, Ulysses, and Pioneers 10 and 11. Dr Humphreys addresses some comments to a recent study that proposes a different solution.

NASA/Ames Research Center Pioneer 10
Pioneer 10

R.H. from the United States writes:

Question for Dr. Humphreys—Your cosmology suggests an original solution to the “pioneer anomaly”, but last year it was reported that it was solved without invoking a change in physics. It seems interesting to me that it took such a long time to solve something with such a seemingly obvious answer as the effects of heat. At any rate, I haven’t heard of any responses from creationists, which might imply that it’s agreed upon universally. But, I have to ask, is it a satisfactory answer, or is it still a useful argument for creation?

Dr Russ Humphreys responds:

Dear Mr. H.:

Thanks for your interest in this topic. Yes, I’ve been aware of the alleged answer to the Pioneer slowdown since it came out in Physical Review Letters last June ( It is merely the latest in a long series of attempts to try to explain the anomaly with heat radiated excessively in the forward direction. The paper shows a graphic of hot and cold spots on the spacecraft from a computer simulation, but it offered no details on the simulation itself … yet it is crucial to the result they claim. The principal author, Slava Turyshev, e-mailed me on September 23 that his team was preparing a paper with the heat simulation details, but as of today Google Scholar can’t find it on the Internet, not even a preprint.

I’m suspicious of their result for several reasons:

  1. Back-of-envelope calculations I’ve done on the heat radiated make it seem unlikely. I’ve acquired a detailed report on the Pioneer physical structure, and I hope I can find enough details related to heat emission from various parts to do a better calculation.
  2. A graph of radar data in their paper shows the anomalous deceleration leveling out, not steadily declining (as they interpreted the graph). The value it levels out at is almost exactly the presently-observed/accepted value of the Hubble constant H times the speed of light c, even closer than in the earlier reports of the deceleration. To have “heat” accidentally give a number with such cosmic significance seems highly unlikely to me.
  3. Pioneers 10 and 11 were not the only spacecraft to show the anomaly. Galileo and Ulysses also showed about the same deceleration, but less clearly because they didn’t get as far from the Sun. Their structures were quite different from each other and from the Pioneers. How likely is it that they would accidentally radiate the right amounts of forward heat necessary to give decelerations also on the close order of Hc?

I’m waiting to see the alleged detailed thermal analysis from Turyshev et al. If it doesn’t materialize in a year or so, that will tell me they found a flaw in their analysis, and I’ll re-visit the issue in print. If it does materialize, I’ll go over it carefully and submit an update, possibly a letter, to Journal of Creation. In short, I think my explanation of the anomaly is still good (and some tweaks from my recent cosmology work may make it even better), but I can’t guarantee that yet.

Cordially in Christ,

Russ Humphreys

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Readers’ comments
James S., United States, 13 May 2013

Great article. Appreciate it much. Thank you Dr. Humphreys for your valuable work and thanks to CMI for keeping us informed.

Jeannette P., United Kingdom, 11 May 2013

I have learned so much from your site, easy to use and abundant resources showing that Creation is not only a fact because God says to but that there is much scientific evidence for the truth of the Bible and against the idea of Evolution.

However, not having much understanding of cosmology, I found this and other articles on the subject hard to follow. You are saying?:

1. The Pioneer anomaly shows that universe is still expanding but does have an edge.

2. It shows that the earth is near the centre of the universe.

3. You are saying that the anomaly is caused by a “gravitational well” produced by the difference between the centre and the edge. This pulls any object, such as a spacecraft, towards the centre of the universe, which would be seen as a slight deceleration.

Is that correct?

However, this linked article from the Journal of Creation says: the ‘Pioneer effect’, is “an apparent small Sunward anomalous acceleration of the Pioneer 10 and 11 spacecraft.”

I thought it was a Deceleration???

A final question: Why should some try to explain away the anomaly by heat distribution? How could that affect the acceleration of the spacecraft?

Russ Humphreys responds

Dear Ms. P.: I'm glad you are thinking about this. Of your numbered points, only the second sentence of point 3 is incorrect. According to my theory, it's not gravitational force (which would be far too small) that decelerates the spacecraft. Instead, it's a general relativity effect, the shrinking of radar distances due to the increase of gravitational potential throughout the whole cosmos inside the waters.

On acceleration versus deceleration, you've been fooled by some physics jargon from the first Pioneer report that I allowed into my article. To the physicist, there's only acceleration, no deceleration. To the physicist, the Pioneer's slowdown in its outward plunge away from the Sun is called "an acceleration toward the Sun". A lot of non-physicists looking at this topic have been misled by that jargon. I apologize for the confusion.

Why heat? Well, if the Pioneers fired more infrared photons (heat waves) frontwards than backwards, the recoil (yes, even photons can cause a recoil) would slightly slow down the spacecraft, just as if they had fired some extremely feeble retro-rockets in the forward direction. The question for the Pioneers is, do they radiate enough excess heat in the forward direction to cause the slowdown?

George R., United States, 11 May 2013

Hypothetically speaking, could the apparent deceleration of the spacecraft be explained by an acceleration of the speed of light in the area of space into which they're moving?

Russ Humphreys responds

Interesting thought, Mr. R. But it would probably mean a slower speed of light out there compared to here. For various physics reasons, I would expect the ratio v/c, where v and c are the speeds of the spacecraft and of light, respectively, in a given locality, to remain constant from place to place. So since we see the spacecraft decelerating, the speed of light would also be getting slower and slower as the spacecraft moves further out. Perhaps you were hoping for a faster speed of light out there, so we would then have another solution to the starlight travel time problem. But there are a couple of serious problems with that hypothesis, which is why I haven't advocated it yet.

Obble S., United Kingdom, 11 May 2013

I have been waiting for this article to appear since I heard about the heat being a possible reason, thanks for the info. I am looking forward to the follow up on the data that gives the heat spots.

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