Talk:Pioneer anomaly/Archive for 2008

Coronal mass ejection

In a paper accepted for publication in Astronomy & Astrophysics by Øystein Olsen, he shows that the anomaly is consistent with the delay the *radio signals* experience working through the ejected plasma on their way back to Earth. That's how I understand his press release (in Norwegian), anyway. Kjetilho 01:03, 29 December 2006 (UTC)

No, he says that

The Doppler data itself can not be used to distinguish between a constant acceleration model and acceleration proportional to the remaining plutonium in the radioisotope thermoelectric generators. There are significant short term variations in the anomalous acceleration. These are shown to be consistent with radio plasma delay from coronal mass ejections.

He made no attempt to explain the anomaly, or otherwise accepted it as an RTG effect. The CMEs were correlated with the variations in the anomaly. When a wave is delayed/refracted by passing through something, it isn't shifted in the long term but rather "bounces back" when the obstacle is removed. Potatoswatter (talk) 13:15, 8 December 2008 (UTC)

Why it is called "anomaly"?

The Pioneer "anomaly" is the same as "cosmological redshift" and that latter is explained by Einsteinian physics. So why it is still called "anomaly"? It is only anomaly in Newtonian physics since it does not have any explanation there but it confirms Einstein's physics. It's theoretical value is $c^{2}/R$, where R is "Einstein's Radius", 4.3 Gpc. So its theoretical value according to Einstein's gravitation should be $7\times 10^{-10}m/s^{2}$. Am I doing something wrong here? Jim 20:01, 28 March 2007 (UTC)

The only Einstein radius I'm familiar with is the formula for calculating the size of a gravitationally lensed ring given mass M. What are you referring to?Maury 21:28, 18 April 2007 (UTC)

the anomaly is a blueshift. Potatoswatter (talk) 13:17, 8 December 2008 (UTC)

update tag.

I put the update tag in the article as the June 2007 date has passed, have we concluded anything?

Also during a bit of research, I found a scheduled meeting for next year: [1] . Can we put this into the article somewherE? Capuchin 08:20, 19 July 2007 (UTC)

Update tag removed. The article isn't outdated, it simply might be lacking the latest speculation. Potatoswatter (talk) 12:50, 8 December 2008 (UTC)

sunward acceleration?

Er, please forgive me for not being a scientist, but the article doesn't explain what is meant by a "constant sunward acceleration". Since the Pioneers are, I assume, traveling away from the sun, then how can they be accelerating towards it? Maybe something could be added to the article to clear this up? 70.20.149.174 (talk) 02:57, 3 March 2008 (UTC)

They are moving away from the Sun, but at slower and slower speeds due to the Sun's gravity. The anomoly is that they are being slowed slightly more than they should, as if there is a small additional force/acceleration towards the Sun. Someone could explain that more concisely in the article. Bubba73 (talk), 03:10, 3 March 2008 (UTC)

I admit that when I first heard "Pioneer accelerating towards the sun", the first thing I imagined is what you'd think when you read that. It took me a minute to realize it was a relative acceleration, and I only took that minute to think about it because I know which direction Pioneer is actually travelling. Its important that Wikipedia not be written for people who already know this information, or its use degrades to nil. It must be an encyclopedia and although detailed scientific explanation is appreciated within the body of the article, the topic statement must be clearly defined and understandable, even for someone who knows very little about the subject. Just my opinion. 207.154.101.37 (talk) 07:10, 5 March 2008 (UTC)

OK, I changed the initial paragraph to make this more clear (I hope). LouScheffer (talk) 18:20, 5 March 2008 (UTC)

Don't all orbital satellites spend their time about split between moving toward and away from the sun? JD Lambert^(T|C) 16:06, 6 March 2008 (UTC)

Not all. Once they reach escape velocity, as these have, they just keep going out. The sun's gravity slows them down, but will never add up to enough to make them reverse directions. LouScheffer (talk) 17:25, 6 March 2008 (UTC)

Coverage in The Economist

None other than The Economist covered a part of this topic recently : [2]. Perhaps it should be added in the refs or such. --Childhood's End (talk) 21:23, 7 March 2008 (UTC)

The solar system is a binary system

Could are solar system being a two star binary system explain the pioneer effect? i.e. the nemesis hypothesis put forth by doctor Richard A. Muller and others?--Nbritton (talk) 11:08, 14 April 2008 (UTC)

That would not explain why the effect is seemingly similar on both crafts. Plus, it's kind of unrealistic to presume that an entire sun has been overlooked in the local vicinity. Jefffire (talk) 12:54, 14 April 2008 (UTC)

Unless you would consider the 'local vicinity' our entire galaxy the star wouldn't be. It is possible we can't see it... read nemesis hypothesis for more. - Anon —Preceding unsigned comment added by 74.237.55.196 (talk) 13:13, 15 April 2008 (UTC)

That's even more silly. If it's having an effect on the craft it would need to be near given that gravity weakens at an inverse square. Jefffire (talk) 14:36, 15 April 2008 (UTC)

Jiffire - The nemesis wiki says we might not see a brown dwarf and if it exists it will be easily found in "the upcoming WISE mission (scheduled for June 2009)". interesting idea

Anon - at least read an article before you refer to it :P Way too human (talk) —Preceding comment was added at 21:30, 17 April 2008 (UTC)

This isn't a general debate on the nemesis hypothesis. A user asked if it was a plausible explanation for the pioneer anomaly. Jefffire (talk) 21:40, 17 April 2008 (UTC)

"Plus, it's kind of unrealistic to presume that an entire sun has been overlooked in the local vicinity." looks like i'm not the only one who needs to remember that. now i'm just bitter, forgive me, enough's been wasted here. Way too human (talk)

On the idea of a binary star system.

1) It has been discovered that approximately half the the observable stars in the sky are binary star systems so it's not such a far out idea that our own sun is in a binary star system. It is at least plausible.

2) It has been observed that the sun is missing a significant amount of angular momentum. That is to say, the sun is not spinning fast enough to account for the total angular momentum of the solar system or it's own mass. There are two kinds of angular momentum: spin momentum and rotational momentum. If spin momentum is missing from the sun, then it must have rotational momentum. The sun must be curving through space in order to account for the sun's missing angular momentum.

3) When two masses are attracted and rotate about a center of mass, each mass observes a centripetal force directed to the center of mass of the system proportional to 1/r (not 1/r^2 per the mutual gravitational pull of the two masses). Again, the centripetal force(1/r) is directed toward the center of mass of the system. The gravitational force(1/r^2) is directed toward a mass. There are two cases. One example is when the center of mass is inside the much larger mass in which case the smaller mass is observed to simply rotate about the much larger mass as is the case of the earth and the sun. The other case is when the two masses are of similar scale and the center of mass is not found inside either mass but is found somewhere in space between the two masses. In this case, the two masses are in elliptical orbits about the center of mass of the system and the center of mass would be closer to the sun than the other mass and the centripetal force would fall off as 1/r (instead of 1/r^2) making it possible to account for the anomalous force. —Preceding unsigned comment added by Mabell108 (talk • contribs)

Anomaly and Comets

If Pioneer really is following a different trajectory, and it's not due to mechanical failure or reading the data incorrectly, then wouldn't that also imply that the calculated trajectory of comets we know about also be slightly incorrect? Infonation101 (talk) 21:10, 14 April 2008 (UTC)

Yes, but comets distances cannot be measured nearly as precisely, because they do not carry transponders or precise oscillators for use as time standards. Wwheaton (talk) 16:33, 14 October 2008 (UTC)

Quantum Gravity Waves

If you accept both Einstein's theory that gravity around massive objects is actually a curvature of space and time accelerating matter toward the massive object, and you accept the presence of vacuum energy (dark energy), then is easy to imagine very dense vacuum energy generating the same curvature of space and time accelerating matter toward the dense energy (accelerating matter outwardly in all directions at once, which can be felt as inertial forces, resistance to change in motion). We can then 'feel' vacuum energy gravity when we accelerate in the weightlessness of space, and when we resist the force of Earth's gravity we are experiencing both curvatures (matter gravity accelerating matter downward toward Earth and vacuum energy gravity resisting acceleration forces). Some work being done at open source project http://www.BigCrash.org, including speculation that vacuum energy might flow into black holes. --Jtankers (talk) 14:32, 16 April 2008 (UTC)

Speculation, if dark energy is dense enough to cause its own powerful gravity, (if it is the force that gives matter inertia by resisting change in motion), and if large objects like the sun create waves of density in the dark energy (similar to a wake left by a speeding boat on a pond, but in 3d), then perhapses the energy density waves caused by the sun moving through the dark energy field might subtlety affect motion of space craft. --Jtankers (talk) 14:32, 16 April 2008 (UTC)

Is this anomaly force really stable (8.74 ± 1.33) × 10^−10 m/s2) ?

• Or is this an average based on several measurements?
• When will NASA release the exact data: dd/mm/yy for measurements and the exact measured deviance of velocity? —Preceding unsigned comment added by Bjarne Lorenzen (talk • contribs) 12:34, 22 July 2008 (UTC)

The anomaly is not measured per se. It is inferred. What is being measured is the frequency of the radio signal received from the spacecraft; tens of thousands of data points over the span of several years. This same frequency is then calculated using an orbital model that takes into account the laws of celestial mechanics, nongravitational effects, effects on signal propagation, the location of receiving stations, you name it. The finding is that the computed and observed frequencies cannot be reconciled unless one supplements the force model with something. When that something is assumed to be a constant sunward acceleration of 8.74 × 10^−10 m/s^2, good agreement with the data is achieved. The one-sigma error of 1.33 × 10^−10 m/s^2 is a combined error budget that includes statistical fitting errors, rounding errors, physical uncertainties, etc. --Vttoth (talk) 02:16, 31 August 2008 (UTC)

5,000 km/yr

The specification of the deviation per year has been added here. The value is apparently taken from this blog article, the author of which apparently took it from here (see first two responses). However, the calculation

Δx = 1/2 a t² = 0.5 × 8.74 × 10⁻¹⁰ m/s² × (365.25 × 24 × 60 × 60 s)² ≈ 435.2 km

shows clearly a much smaller result. Can someone explain this? --80.129.78.14 (talk) 15:12, 18 September 2008 (UTC)

I stumbled upon this discrepancy independently, so you are likely to be right. I will change the article. I also find the sentence "This results in the spacecraft being about 5,000 km closer to the sun than they should be, every year." hard to understand. I'll try to improve it. --Art Carlson (talk) 08:36, 12 November 2008 (UTC)

Vacuum Modified Gravity and other not-yet-discussed theories

There are many (>100) different theoretical proposals for the Pioneer anomaly on arXiv alone. Wikipedia's point is to present a summary to the reader, and so cannot include them all. So which ones to include?

This is a problem for almost all articles, and not just the Pioneer anomaly alone. The normal Wikipedia standard is that someone, not the author, comments on the proposed inclusion in a reasonably reputable and verifiable place.

This has nothing to do with whether an idea is correct or not, or a valuable contribution, just a more-or-less objective way of deciding what should go in an encyclopedia. LouScheffer (talk) 11:31, 25 September 2008 (UTC)

I think that Masreliez, C. Johan (2001), http://www.estfound.org/ doesn't belong to here. He selectively "solves" a lot of old anomalies, many of them already solved in other ways, such as the too-old globular clusters, the spiral forms of galaxies, and introduces much-much worse ones, such as that earth must have been at distance of 2 AU from sun in the early solar system 4.5 Ga ago, such as the stars fall in spiral into the center of the galaxy in a time span of undefined (maybe 400 Ma, since the stars are assumed to follow the spiral form), such that when correlating with the stars orbit vectors around the center it is very hard to not conclude that sun was born very far outside Milky Way. Unless there are very serious objections, I'll remove that ref soon. Said: Rursus (☻) 13:12, 12 October 2008 (UTC)

While you're at it, could you please review this addition? From what I can tell, it also doesn't meet the requirements for inclusion, but the contributor emailed me requesting a review. Thanks. --Ckatz^chat_spy 19:23, 12 October 2008 (UTC)

Well, the latter is a clear violation of WP:WEIGHT: including a huge discussion sourced to the ICR (that is, the Institute for Creation Research, a Creationist think-tank) rather than a physics journal or otherwise reliable third-party source. siℓℓy rabbit (talk) 19:43, 12 October 2008 (UTC)

I also looked at this, can could find no references in arXiv, or citebase, or google scholar (which are fairly inclusive) where anyone discusses the plusses and minuses of this theory. Without this third party discussion, it's not received enough discussion to appear in an encyclopedia article. LouScheffer (talk) 03:35, 13 October 2008 (UTC)

Someone was faster than me! Thank you guys: Well done! Said: Rursus (☻) 14:02, 14 October 2008 (UTC)

Forgot to say: creationism? Not in this article. There are dedicated articles for religion, this is science. Said: Rursus (☻) 14:05, 14 October 2008 (UTC)

Aethereal Gravitation Theory

The reference to "Aethereal Gravitation Theory" seems to hold as much water as the timecube theory. I can not find any credible sources other than the linked website: "Site created to explain a completely new theory of gravity". Yeah, sure. Perhaps someone should add the FSM to this page. —Preceding unsigned comment added by 86.211.43.70 (talk) 19:57, 11 November 2008 (UTC)

Cosmological constant

The observed cosmological constant also cannot explain the Pioneer anomaly because it is many orders of magnitude too small and has the wrong sign (repulsive instead of attractive).

I agree that the cosmological constant, or, more precisely, dark energy, which may not actually take the form of a cosmological constant, is much too small to account for the anomaly. I have my doubts about the sign, though. Dark energy has negative pressure, which results in an acceleration of the universe, but it has positive energy density, so it is not clear what sign the acceleration should have, or whether it should be zero because of the uniform distribution of dark energy in space. Unless we can cite a RS, it is safer not to speculate on this. --Art Carlson (talk) 09:01, 12 November 2008 (UTC)

I wrote that because in the Newtonian approximation you can model a cosmological constant as a repulsive acceleration proportional to distance, and I figured the Newtonian approximation would be good enough here. In fact, the exact geodesics through the origin (x = t = 0) in de Sitter space (ds² = dt² − e^2kt dx²) are χ(t) = (v_o / k) sinh(kt), where χ = e^kt x is the metric distance from the origin at the time t. This is not only always accelerating away from the starting point, it's exactly what you get in the Newtonian approximation.

But now I think I was wrong, because when I calculate the redshift of an object moving along one of those geodesics as seen by someone at rest at the origin, I get (exactly)

$1+z(t)={\frac {1}{1-v_{o}\ {\text{sinh}}(kt)}}{\sqrt {\frac {1+v_{o}e^{-kt}}{1-v_{o}e^{-kt}}}}$

where t is the coordinate time of emission. z'(t) can be positive or negative, so the apparent acceleration (if it's calculated as c dz/dt) can be either towards or away from the origin, even though χ''(t) is always directed away. The crossover from apparent deceleration to apparent acceleration happens at t ~ v_o²/k, and weirdly enough t ~ v_o²/k for the Pioneer anomaly (1/k ~ 10¹⁰ years, t ~ 10¹ years, v_o ≈ 10^−4.5), so I can't get a reliable sign from this toy model. But the magnitude is k² v_o t < 10⁻²² m/s², so it hardly matters.

I know all this is OR (I'm just posting it here because I thought it was interesting), but can we put back just a claim that the CC is far too small (if the dark energy is a CC), leaving out the bit about the sign? -- BenRG (talk) 00:52, 13 November 2008 (UTC)

If nobody else has written about the (lack of) connection between the Pioneer anomaly and the cosmological constant, then what we are doing here is indisputably OR. Still, I've done similar things in other articles and believe it can be a service to the reader, but it must be done with a light touch. All we really know about CC/DE is (1) that there is a big chunk of mass density in the universe that we can otherwise identify (mostly from CMB), and (2) that the expansion is accelerating (SNe). The mass density doesn't play any direct role here, but the acceleration is a direct measurement. I'd be good with mentioning the measured acceleration of the universe and juxtaposing that number with the acceleration of the Pioneer anomaly. That should be enough to convince speculating readers that this is not fruitful terrain, regardless of the proper way to do the theory.

You may have noticed that I am running on the ragged edge of my knowledge of both theoretical and experimental cosmology. I leave the final choice up to you. --Art Carlson (talk) 08:59, 13 November 2008 (UTC)

New Paper from 2-28-08 - American Institute of Physics

http://www.aip.org/pnu/2008/split/857-2.html

A new look at the trajectories for various spacecraft as they fly past the Earth finds in each case a tiny amount of surplus velocity. For craft that pursue a path mostly symmetrical with respect to the equator, the effect is minimal. For craft that pursue a more unsymmetrical path, the effect is larger. In the case of the NEAR asteroid rendevous craft (<http://near.jhuapl.edu/>), for instance, the velocity anomaly amounts to 13 mm/sec. Although this is only one-millionth of the total velocity, the precision of the velocity measurements, carried out by looking at the Doppler shift in radio waves bounced off the craft, is 0.1 mm/sec, and this suggests that the anomaly represents a real effect, one needing an explanation.

Some ten years ago another anomaly was identified for the Pioneer 10 spacecraft (see http://www.aip.org/pnu/1998/split/pnu391-1.htm) and a certain amount of controversy has clung to the subject since then. One of the researchers on that earlier measurement is part of the new study, conducted by Jet Propulsion Lab scientists. John D. Anderson (jdandy@earthlink.net, 626-449-0102) says that the JPL scientists are now working with German colleagues to search for possible velocity anomalies in the recent flyby of the Rosetta spacecraft. (Anderson et al., Physical Review Letters, upcoming article; designated as an editor’s suggested articlePhysical Review Letters)

—Preceding unsigned comment added by 71.30.178.176 (talk) on 04:30, 1 March 2008 (UTC)

Weyl geometry explanation has been corrected

The author of the Weyl geometry based explanation has posted on arxiv a correction of his previous explanation, stating that it cannot hold, see http://arxiv.org/abs/astro-ph/0701132 —Preceding unsigned comment added by 130.186.18.218 (talk) on 10:17, 11 March 2008 (UTC)