Re: [asa] Near Starlight Problem; Adam would never see all of Orion's belt?

Hi David,   Dark matter halos are well established as to their existence.  Last year, a major study shows numerous subgroupings of dark matter concentrations within the halo of the Milky Way.  This halo extends from about 65,000 light years from center to about 300,000 light years.    http://www.usatoday.com/tech/science/space/2008-08-18-milky-way-star-streams_N.htm   We have to go back to 1933 (Fritz Zwicky) regarding dark matter proposals.   He discovered that galaxy clusters should be flying apart if no dark matter were present.  Vera Rubin was first, I think, in the 50’s to discover non-Keplerian rotation rates in galaxies.  MOND (MOdified Newton Dynamics) is one theory that tweaks Newton’s laws to correct galactic motion.  However, MOND is not all that popular, apparently, since, for instance, it requires the addition of dark matter to explain why galactic clusters stay together.   Regarding spacecraft anomaly, there is only a slight deceleration variation of about 8.5 x 10^-10 m/s^2 for the Pioneer 10 spacecraft.  There could easily be other reasons besides quirks in the laws of physics to explain this, though no clear answer is known yet.  :) "Coope" ________________________________ From: David Clounch <david.clounch@gmail.com> To: Christopher Sharp <cmsharp01@aol.com> Cc: igd.strachan@gmail.com; TDavis@messiah.edu; asa@calvin.edu Sent: Saturday, February 21, 2009 7:45:28 AM Subject: Re: [asa] Near Starlight Problem; Adam would never see all of Orion's belt? > All the stars are moving around the center of the Galaxy in exactly in > accordance with the general gravitational field of the Galaxy, aside from > modifications of stars in star clusters. I dont know about the Milky Way, but this isnt true for all other galaxies. John D. Anderson (of JPL) writes in Astronomy,  March 2009: "Since the 1970's astronomers have known that the outer regions of galaxies appear to violate Newton's gravity laws. We would expect the stars in a galaxy's outer regions to travel in elliptical orbit's with their orbital speeds decreasing with increasing distance. However, this is not observed. Instead of decreasing, the speeds are essentially constant over a wide region of the galaxy." "Astronomers hypothesized that the galxies actually contain large quantities of unseen material  that hold the stars in the galaxy. This extra mass -- called dark matter because it interacts via the gravitational force while remaining impossible to to directly observe -- brings the dynamics into agreement with Newton." Anderson's article is called "Is there something we don't know about gravity"  and he points out that the Pioneer spacecraft which are now headed out of the solar system are off course by up to 32,000 miles. He references Physical Review Letters, March 7, 2008, where he and four other JPL scientists discuss whats wrong with the theory of gravity. Six spacecraft which have done flybys of the earth for gravity boost are accelerating at the wrong rate.  He suggests that a new theory of gravity may be needed. We still live in exciting times!  Dark matter may disappear. To unsubscribe, send a message to majordomo@calvin.edu with "unsubscribe asa" (no quotes) as the body of the message.

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Received on Sat Feb 21 22:10:00 2009