(urth) grumble at wolfe comment made attached to guardianarticle

[Gerry Quinn]

From: "Jeff Wilson" <jwilson at io.com>
> On 2/9/2011 9:59 AM, Gerry Quinn wrote:
>> From: "Jeff Wilson" <jwilson at io.com>
>>> On 2/9/2011 6:26 AM, Gerry Quinn wrote:
>>
>>>> I think horseshoes are a bit problematic. If you look at Cruithne's
>>>> orbit, its actual distance from Earth varies on a short scale with a
>>>> period of one year. Over a longer term, the average distance varies.
>>>> Since Cruithne's orbital period is one year, there's no room for
>>>> meaningful six-year conjunctions.
>>>
>>> That's because tiny Cruithne is too small to influence Earth in a
>>> detectable way. Janus and Epimethius, however, are similar in mass and
>>> do their thing in four years.
>>
>> But their orbital period around Saturn is only 0.7 days... so those four
>> years are equivalent to about 2000 years on Blue!
>
> That may depend heavily on odd power functions, like the orbital period 
> formula earlier; the dual orbit discovery was pre-internet (1978) so I'm 
> having a devil of a time locating anything analytical about it.

I think it's going to be a general property of horshoe orbits that the 
period between conjunctions will be very long compared to the orbital 
period.  The reason being that the two objects are essentially in the same 
orbit, albeit going a little faster or slower at times.  So their orbital 
speeds cannot differ much, and can only catch up or fall behind over a 
period of many orbits.

- Gerry Quinn