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Thursday, April 13, 2006

Physics: Nagging Little Discrepancies

An interesting paper was posted yesterday on arXiv, “Is the physics within the Solar system really understood?” which summarises the following apparent anomalies for which there are varying degrees of experimental evidence:
  1. Dark matter
  2. Dark energy
  3. The Pioneer anomaly
  4. Excess velocity increase of spacecraft which fly-by Earth
  5. Apparent secular increase in the astronomical unit (about 10 metres/century)
  6. Quadrupole and octupole power in the cosmic background radiation correlated and aligned with the ecliptic
I was unaware of 4, and 5 and hadn't heard much about 6 recently although it was rumoured something interesting might be in the three year WMAP data. This paper does not cite that data release.

Wouldn't be interesting if all of these effects could be explained by the choice of too large a numerical integration step in a simulated universe? Note that items 3 and 4 both involve small apparent discrepancies in the motion of man-made objects which move more rapidly than most natural bodies on such geodesics—the creator (or, perhaps I should write, more reverently, “Creator”) of a simulation who chose a time step suitable for planetary motion (for example, the 1/100th day integration step I used in the Quarter Million Year Canon computation) might just find themselves caught out by pesky in-simulation sentients who made precision measurements of high-speed gravitational assist maneuvers or objects on hyperbolic trajectories.

Here are a few questions for physicists and numerical integration experts. Is the choice of an insufficiently fine integration step likely to produce discrepancies of the sign and magnitude observed in the Pioneer, fly-by, and astronomical unit anomalies? How large an integration step would be required to produce the deviations from general relativity in each case? Are they all the same, or related in a simple way? Are there observations of solar system bodies (for example, sun-grazing comets on hyperbolic escape trajectories or close asteroidal encounters with planets) which could exclude (or provide evidence for) this hypothesis?

Posted at April 13, 2006 14:30