Dark matter article on BBC website

capnrob97
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[AF>France>TDM>Centre]Jeannot Le Tazon
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Dark matter article on BBC website

Thanks.
And on the NewScientistSpace site an other one about dark matter and dark energy :
http://www.newscientistspace.com/article/mg18925423.600-three-cosmic-enigmas-one-audacious-answer.html

tullio
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RE: Dark Matter I


I simply do not believe in dark matter. Our dynamical equations may be wrong at large distances. I have read that one of Pioneer spacecrafts is not where it should be according to newtonian dynamics. Has anybody any news on this?
Tullio

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RE: RE: Dark Matter I

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I simply do not believe in dark matter. Our dynamical equations may be wrong at large distances. I have read that one of Pioneer spacecrafts is not where it should be according to newtonian dynamics. Has anybody any news on this?
Tullio

What is dark matter? I think it is just mass without a light source. It is being found all the time. The equations may be wrong as well, but new unlit matter is found weekly it seems. Its hard not to believe in it when it keeps popping up.

Chipper Q
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Good articles, thanks for the

Good articles, thanks for the posts. The second one, regarding 'quantum critical phase transition' and 'dark energy stars' is quite an elegant solution if it turns out to be the case.

Tullio, last I checked, the variation in position might just be systematic. The Voyager spacecraft should be the first 'Interstellar' craft. Real good lecture by Dr. Edward Stone (given on 11/6/2002) called "The Voyager Journeys to Interstellar Space" here. Also lots of other really good lectures, including one on LIGO by Dr. Barry Barrish (given on 3/5/2003)... another good one on Spitzer, which should come in very useful if dark matter's at 10,000 degrees...

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RE: What is dark matter? I

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What is dark matter? I think it is just mass without a light source. It is being found all the time. The equations may be wrong as well, but new unlit matter is found weekly it seems. Its hard not to believe in it when it keeps popping up.


That's pretty well right!
The 'dark matter' idea originated in the study of galaxies. If you plot the tangential velocity of stars orbiting a galactic centre, as obtained by observations, then for a lot of galaxies you wind up with a persistence of velocity well out from the centre. If you model the dynamics with known laws using the visible matter then the prediction is: velocity going proportional to the inverse square root of radius ( I think, from memory ). Whereas observational data show a basically 'flat' curve out to quite significant radii before it falls off. Either your model is wrong ( new physics ), or the mass distribution is not reflected by the visible stuff ( new physics too ). It's not a bad concept really, but just reflects our ignorance - a bit like 'quasars' which was a label long used before knowledge of their real character.
The main thing is to not confuse it with 'dark energy' which, as I have previously asserted, originates from the Australian Tax Office ......

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

tullio
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RE: Good articles, thanks

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Good articles, thanks for the posts. The second one, regarding 'quantum critical phase transition' and 'dark energy stars' is quite an elegant solution if it turns out to be the case.

Tullio, last I checked, the variation in position might just be systematic. The Voyager spacecraft should be the first 'Interstellar' craft. Real good lecture by Dr. Edward Stone (given on 11/6/2002) called "The Voyager Journeys to Interstellar Space" here. Also lots of other really good lectures, including one on LIGO by Dr. Barry Barrish (given on 3/5/2003)... another good one on Spitzer, which should come in very useful if dark matter's at 10,000 degrees...


This is a quotation from New Scientist, March 19, 2005
THIS is a tale of two spacecraft. Pioneer 10 was launched in 1972; Pioneer 11 a year later. By now both craft should be drifting off into deep space with no one watching. However, their trajectories have proved far too fascinating to ignore.

That's because something has been pulling - or pushing - on them, causing them to speed up. The resulting acceleration is tiny, less than a nanometre per second per second. That's equivalent to just one ten-billionth of the gravity at Earth's surface, but it is enough to have shifted Pioneer 10 some 400,000 kilometres off track. NASA lost touch with Pioneer 11 in 1995, but up to that point it was experiencing exactly the same deviation as its sister probe. So what is causing it?
I cited Pioneer from memory.
Tullio
PS See also New Scientist, 25 January 2006,"Gravity theory dispenses with dark matter". It refers to the previous article.

Chipper Q
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Tullio, I think the Pioneer

Tullio, I think the Pioneer craft are reported to be slowing down (or accelerating towards the center of the solar system). Here's a link to a Jan. '06 update from the Planetary Society: Update From the Pioneer Anomaly Team

tullio
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RE: Tullio, I think the

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Tullio, I think the Pioneer craft are reported to be slowing down (or accelerating towards the center of the solar system). Here's a link to a Jan. '06 update from the Planetary Society: Update From the Pioneer Anomaly Team


Thanks, Chipper, you are always well informed. I wonder why the NASA sites on Pioneers never mention this anomaly.
Tullio

Chipper Q
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RE: RE: Tullio, I think

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Quote:
Tullio, I think the Pioneer craft are reported to be slowing down (or accelerating towards the center of the solar system). Here's a link to a Jan. '06 update from the Planetary Society: Update From the Pioneer Anomaly Team

Thanks, Chipper, you are always well informed. I wonder why the NASA sites on Pioneers never mention this anomaly.
Tullio


Here's a link to the Pioneer Mission Status page. I think the reason the missions are over is because the craft stopped responding/communicating. The power supply on the Voyager craft should keep working until about 2020, and hopefully the craft will have journeyed out of the heliosphere and into actual interstellar space by then, providing data the whole way. Not sure about any data on concentrations of dark matter, though...

tullio
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RE: RE: RE: Tullio, I

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Quote:
Quote:
Quote:
Tullio, I think the Pioneer craft are reported to be slowing down (or accelerating towards the center of the solar system). Here's a link to a Jan. '06 update from the Planetary Society: Update From the Pioneer Anomaly Team

Thanks, Chipper, you are always well informed. I wonder why the NASA sites on Pioneers never mention this anomaly.
Tullio

Here's a link to the Pioneer Mission Status page. I think the reason the missions are over is because the craft stopped responding/communicating. The power supply on the Voyager craft should keep working until about 2020, and hopefully the craft will have journeyed out of the heliosphere and into actual interstellar space by then, providing data the whole way. Not sure about any data on concentrations of dark matter, though...


Also the language used to program the hardware aboard these long missions may be a problem, since there is nobody who knows it after 30 years. All programmers who wrote it may be out of reach. I read of a similar problem with the hw used by the Federal Aviation Administratiom, and written in Jovial. Did you ever hear of it?
Tullio

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