# "Dark matter": methinks not **URL:** \ **Category:** Great Debates\ **Created:** [March 25, 2004, 4:50am UTC](https://boards.straightdope.com/t/dark-matter-methinks-not/236284 "2004-03-25T04:50:29Z")\ **Posts on this page:** 3\ **Page:** 2
**Author:** ![bonzer](https://avatars.discourse-cdn.com/v4/letter/b/45deac/32.png) [@bonzer](https://boards.straightdope.com/u/bonzer)\ **Post date:** [March 28, 2004, 11:18pm UTC](https://boards.straightdope.com/t/dark-matter-methinks-not/236284/21 "2004-03-28T23:18:07Z")
> [@cityboy916](#): > > (Apparently, Discover also misprinted Milgrom’s first name; the lecture you cited refers to him as Mordehai whereas the Discover article calls him Moti.) [No they didn’t](http://www.weizmann.ac.il/acadsec/Scientific_Activities/current/Condensed_Matter_Physics.html); Moti seems some sort of diminuative for Mordehai. > [@](#): > > Since Sedna’s orbit is calculated to be quite eccentric, I must surmise that it is orbiting much too fast to maintain its current distance from the Sun and is expected to recede farther into space after it reaches perihelion. Correct. > [@](#): > > My question is whether the calculations which give its 6 orbital parameters would be severely messed up if the Sun’s gravitational pull at each instant was squared. It’s actually **7** parameters - a position, a velocity and a time. Taking the question at it’s most extreme, sure. But _what would that explain_? There’s nothing about Sedna’s orbit that’s remotely in violation of Newtonian dynamics. ---
**Author:** ![umop\_ap\_sdn](https://avatars.discourse-cdn.com/v4/letter/u/dbc845/32.png) [@umop\_ap\_sdn](https://boards.straightdope.com/u/umop_ap_sdn)\ **Post date:** [March 28, 2004, 11:48pm UTC](https://boards.straightdope.com/t/dark-matter-methinks-not/236284/22 "2004-03-28T23:48:10Z")
> [@bonzer](#): > > [No they didn’t](http://www.weizmann.ac.il/acadsec/Scientific_Activities/current/Condensed_Matter_Physics.html); Moti seems some sort of diminuative for Mordehai. Thank you; that clears up my confusion. > [@](#): > > It’s actually **7** parameters - a position, a velocity and a time. > Taking the question at it’s most extreme, sure. But _what would that explain_? There’s nothing about Sedna’s orbit that’s remotely in violation of Newtonian dynamics. The 6 parameters I was referring to are semi-major axis, inclination of orbit, eccentricity, ascending node, argument of perihelion, and mean anomaly. Are you saying average orbital velocity is the 7th? Makes sense; it’s not redundant if the mass of center (or effect of the mass of center at low accelerations) is unknown. So either a solution only exists for Newtonian gravity, or two solutions exist, one for Newtonian and one for MOND. Eventually, as **Thaumaturge** said, we will see which solution ends up being the best fit, and MOND will either be proven or disproven to affect orbits at that distance. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [March 29, 2004, 1:00am UTC](https://boards.straightdope.com/t/dark-matter-methinks-not/236284/23 "2004-03-29T01:00:51Z")
> [@](#): > > Since NASA is still in contact with Voyagers 1 & 2 do these probes show tracking anomalies as well, can they be used to explore this phenomena I think both Voyagers are further away then the pioneers (due to greater speed, mainly from stealing more speed from planets). and I have heard that they are encountering some ‘slowdown’. I seem to recall the solar wind forming a barrier of sorts against the ‘galactic’ wind pressing inwards, perhaps this is the cause of the slowing. Or maybe the sun somehow protects against cronoton waves that convert matter into thrusters and are slowly eating away at our probes, and ‘pushing them back’. [Previous page](https://boards.straightdope.com/t/dark-matter-methinks-not/236284.md?page=1)