The Pioneer Anomaly Options

[remcook]

http://www.planetary.org/news/2005/pioneer_anomaly_faq.html

The planetary society may be checking it out...

The Planetary Society has committed to raise the funds to preserve the priceless Pioneer data from destruction.


After years of analysis, but without a final conclusion, NASA, astonishingly, gave up trying to solve the "Pioneer Anomaly" and provided no funds to analyze the data. The Pioneer data exists on a few hundred ancient 7- and 9-track magnetic tapes, which can only be read on "antique" outdated computers. The agency is going to scrap, literally demolish, the only computers able to access and process that data in the next few months!

[Jeff7]

I should point out, however, that MOND was always a phenomenological theory, and its predictions using visible matter would closely match the predictions using GR. In other words, MOND was describing the effects of GR on galaxies, without realising it!

Something else, with modeling something like a galaxy, and failing to take general relativity into account - with a few billion individual stars to model, and if Newtonian physics introduces a tiny amount of error with each star in the model, those small deviations will really compound each other. Each star interacts with others, and if those interactions themselves are in error because of initial errors, etc etc etc - billions of tiny errors add up to one big problem.


It sort of surprised me when I read about this, like "well yeah, duh, general relativity. Why aren't you using it already?" I just think it makes sense, now that we have a theory of relativity, that we actually use it, rather than invent a kind of matter that we just can't directly observe in any fashion.
Relevant image. (I can't take credit, I just found it online somewhere awhile ago.)

But really, we can't disprove dark matter. Star Trek Voyager proved that it existed when they encountered a dark matter asteroid.

[The Messenger]

It sort of surprised me when I read about this, like "well yeah, duh, general relativity. Why aren't you using it already?" I just think it makes sense, now that we have a theory of relativity, that we actually use it, rather than invent a kind of matter that we just can't directly observe in any fashion.
Relevant image. (I can't take credit, I just found it online somewhere awhile ago.)

Three problems with using GR to account for missing galactic mass:

1) GR theoriest did not predict the missing mass - tweaking GR parameters so that they effectively model overaggressive rotational velocities is just curve fitting.

2) Dark matter and energy are needed to literally fill the gaps in the Cosmic Microwave Background. Without dark matter, the CMB power function falls why short of BB model expectations.

3) No gravity waves. Unless and until GWs are detected, all the curve fitting in the world cannot solidify relativistic theory. To date, it can reasonably be argued that we have lacked the needed sensitivity, but this is no longer true. The constraints are such that if LIGO does not detect anything in the next half decade, we are looking down the barrel of another Michelson Morley null.

[Mongo]

Three problems with using GR to account for missing galactic mass:

1) GR theoriest did not predict the missing mass - tweaking GR parameters so that they effectively model overaggressive rotational velocities is just curve fitting.

2) Dark matter and energy are needed to literally fill the gaps in the Cosmic Microwave Background. Without dark matter, the CMB power function falls why short of BB model expectations.

3) No gravity waves. Unless and until GWs are detected, all the curve fitting in the world cannot solidify relativistic theory. To date, it can reasonably be argued that we have lacked the needed sensitivity, but this is no longer true. The constraints are such that if LIGO does not detect anything in the next half decade, we are looking down the barrel of another Michelson Morley null.

1) Since it appears that nobody had ever actually created a GR model of galaxy rotation before last year -- due to the computational difficulty of using full GR -- it is no surprise that no predictions were made. On the other hand, once a GR model was made, it produced results close to observations. No 'tweaking' was required.

2) There are four (2x2) possibilities: GR is accurate or not, and BB models use full GR or not.

If the BB models don't assume full GR, then they are flawed from the beginning, given the results described in the rotation curve papers. If the BB models assume full GR, but GR is inaccurate, then the BB models are worthless. On the other hand, if GR is accurate, then it predicts galactic rotation curves that match observations closely enough that there is no place for dark matter anywhere near a galaxy. Given a choice between GR and dark matter, I will choose GR every time. The CMB power function may well be explained by 'new physics' -- possibly related to the Pioneer Anomoly -- but it does not have to be the currently popular CDM + Lambda.

3) Once gravity waves are conclusively disproven, then we can talk. Until then, I will continue to accept that GR is a closer fit to 'reality' than Newtonian Gravity. In any case, even if GR is disproven, its replacement could very well show similar effects on a galactic scale.

Bill

[ljk4-1]

Paper: astro-ph/0601247

Date: Wed, 11 Jan 2006 20:05:34 GMT (7kb)

Title: Alternative proposal to modified Newton dynamics (MOND)

Authors: Juan M. Romero and Adolfo Zamora

Comments: 4 pages. Accepted for publication in PRD
\\
From a study of conserved quantities of the so-called Modified Newtonian
Dynamics (MOND) we propose an alternative to this theory. We show that this
proposal is consistent with the Tully-Fisher law, has conserved quantities
whose Newtonian limit are the energy and angular momentum, and can be useful to explain cosmic acceleration. The dynamics obtained suggests that, when
acceleration is very small, time depends on acceleration. This result is
analogous to that of special relativity where time depends on velocity.

\\ ( http://arXiv.org/abs/astro-ph/0601247 , 7kb)

[ljk4-1]

I don't want this turning into the Dark Matter/Energy Topic (unless of course that is what is affecting the Pioneer probes), but I wanted to share this news item while we are still on the subject:

Dark Matter Galaxy?

Summary - (Thu, 12 Jan 2006) Astronomers think they might have found a "dark galaxy", that has no stars and emits no light. Although the galaxy itself, located 50 million light years from Earth, is practically invisible, it contains a small amount of neutral hydrogen which emits radio waves. If astronomers are correct, this galaxy contains ten billion times the mass of Sun, but only 1% of this is hydrogen - the rest is dark matter.

http://www.universetoday.com/am/publish/pp...hi.html?1212006

If there is life in that galaxy, just try to imagine how utterly different it probably is from ours.

[ljk4-1]

I don't want this turning into the Dark Matter/Energy Topic (unless of course that is what is affecting the Pioneer probes), but I wanted to share this news item while we are still on the subject:

Dark Matter Galaxy?

Summary - (Thu, 12 Jan 2006) Astronomers think they might have found a "dark galaxy", that has no stars and emits no light. Although the galaxy itself, located 50 million light years from Earth, is practically invisible, it contains a small amount of neutral hydrogen which emits radio waves. If astronomers are correct, this galaxy contains ten billion times the mass of Sun, but only 1% of this is hydrogen - the rest is dark matter.

http://www.universetoday.com/am/publish/pp...hi.html?1212006

If there is life in that galaxy, just try to imagine how utterly different it probably is from ours.

Astrophysics, abstract
astro-ph/0602271

From: Galina Korotkova Gennadievna [view email]

Date: Mon, 13 Feb 2006 08:03:04 GMT (90kb)

Disturbed isolated galaxies: indicators of a dark galaxy population?

Authors: I.D.Karachentsev, V.E.Karachentseva, W.K.Huchtmeier

Comments: 5 pages, 1 figure. Astronomy and Astrophysics, accepted

We report the results of our search for disturbed (interacting) objects among very isolated galaxies. The inspections of 1050 northern isolated galaxies from KIG and 500 nearby, very isolated galaxies situated in the Local Supercluster yielded five and four strongly disturbed galaxies, respectively. We suggest that the existence of "dark" galaxies explains the observed signs of interaction. This assumption leads to a cosmic abundance of dark galaxies (with the typical masses for luminous galaxies) that is less than ~1/20 the population of visible galaxies.

http://arxiv.org/abs/astro-ph/0602271