Looking at the comparisons
here Humphreys figures appear to be a bit off.
Humphreys gives a figure for the moon that is more than 10,000,000 times less than that for Earth. Yet on the site referenced above t he moon's magnetic field is listed as being only 109 times weaker.
[Added in edit - it MIGHT be a typo for 10^9 - but that would still disagree with Humphreys]
The estimates Humphreys gives for Uranus and Neptune are listed as maximum values. Both are larger than the value for Saturn, so it seems that they cannot be "right on" (in fact they are more than 10x the actual figures). It seems likely that his "success" is due solely to making vaguer predictions that were inherently less risky.
Worse, Humphreys relies on Barnes discredited claims about the Earth's magnetic field. See
here for more informationat
This message has been edited by PaulK, 10-04-2005 03:13 AM