Re: PHYSICS/SPACE: Gravity/Time broken?

Amara Graps (
Fri, 1 Oct 1999 09:28:58 +0200

Patrick Wilken ( Thu, 30 Sep 1999 16:00:31 wrote:

>This is a more mundane and reasonble explanation that was published
>on the BBC website a few days ago:
>Tuesday, September 28, 1999 Published at 21:23 GMT 22:23 UK
>Old spacecraft makes surprise discovery

There's more explanations about the Pioneer 10 anomalous acceleration. It's a really active area of research. I would be skeptical of press releases until there's more work done, and then confirmations.

This last Spring, our group had some contact with an Austrailian physicist that believes that the intervening interplanetary dust could have a role in causing the Pioneer 10 anomalous acceleration. The paper was submitted to Phys. Rev. Lett. and you can get it on the astro-ph server:

Here is the abstract.


Authors: David F. Crawford (University of Sydney) Comments: 3 pages, submitted to Phys. Rev. Lett

The reported anomalous acceleration of the Pioneer 10 spacecraft of -8.5X10^{-10} m/s^2 (i.e. towards the sun) can be explained by a gravitational interaction on the S-band signals traveling between Pioneer 10 and the earth. The effect of this gravitational interaction is a frequency shift that is proportional to the distance and the square root of the density of the medium in which it travels. If changes in this frequency are interpreted as a Doppler shift the result is an apparent acceleration directed towards the sun. The gravitational interaction is caused by the focusing of the signal photons in curved space where in this case the curvature is related by the density of the interplanetary dust.


Amara Graps               | Max-Planck-Institut fuer Kernphysik
Interplanetary Dust Group | Saupfercheckweg 1   
+49-6221-516-543          | 69117 Heidelberg, GERMANY *  
      "Never fight an inanimate object." - P. J. O'Rourke