Phantom menace to dark matter theory

New Scientist ^ | Jul 8, 2009 | Marcus Chown

[decimon]

The orbit of the innermost planet, Mercury, departs from what it should be under Newton's laws. A century ago, when Einstein explained this anomaly, it confirmed his theory of gravity - the general theory of relativity.

Now an Israeli physicist predicts that a similar but far more subtle anomaly in the orbits of the planets, if detected, might prove his own theory, known as modified Newtonian dynamics, or MOND. This provides an alternative theory to dark matter to explain why stars orbiting at the edge of spiral galaxies are not flung out into space. These stars are travelling at speeds too fast for conventional gravity from the mass at the heart of a spiral galaxy to hold them in their orbits, so something else must be keeping them on track.

[decimon]

This is the first time I’ve seen a local solar system possibility though.

I'd think that would be the biggie here. It could be investigated with existing gear.

[SuperLuminal]

"This is almost understandable."

OK...Let's see if I've got this straight:

• Dark matter is a crutch to explain outer system failure to launch;
• MOND could explain this problem with the correct choice of acceleration coefficient;
• Newtonian theory would posit a location between a sun and planet where their respective gravitational effects would cancel each other out;
• At the above location, if there is gravity it would prove MOND;
• However, an additional effect (ultimately replacing dark matter??) called a "phantom mass" (dispersed at that!) leading to a "quadrupole" effect needs to be postulated;
• Maybe the Pioneer spacecraft aren't so weird after all; and,
• We need to measure the precise orbit of Neptune for about 1500 years to gather the required data.

OK! Got it...I'll have a proposal and work-plan in the mail in 60-days.

[decimon]

Yeah, but despite all that, this was more understandable than most such. ;-)