Re: inertial/gravitational - real 3-body problem in the news

[Dan Fiscus <***>]

Judith, Tim and all,

Here's a recent news story of a 3-body system in which
1) state-based models are functional and effective, at
least via numerical approximations, and 2) the stakes
and value of this reductionistic, state-based approach
are high. The three bodies are 1) asteroid that may hit
2) the Earth and 3) spacecraft that might alter the
course of asteroid to avoid collision.

(May need a free register to Washington Post to see
this)

http://www.washingtonpost.com/wp-dyn/content/article/2005/11/09/AR2005110902204.html

Devil's advocate issue...maybe we have to be more
specific about right and wrong, maybe by citing utility
or functional value or cost/benefit, etc.?

Dan


Judith Rosen wrote:

> The phrase that grabbed me is "It's not that the state-based equations 
> are wrong..."
snip
> In this instance,/_ his whole point was that the state-based equations 
> ARE wrong._/ They are inherently wrong, if our definition of wrong means 
> "does not commute with reality" but they are able to be less wrong in 
> some contexts and more wrong in others. 
snip
> On Nov 14, 2005, at 10:23 PM, Tim Gwinn wrote:

>     If one pictures a 3-body system, and the set of state-based
>     equations involved, they requires that one body be considered an
>     inertial system being forced by the other two (gravitational)
>     bodies. So we have drawn a box, as it were, around the first body
>     and said: this is the system, all else (namely, the two other
>     bodies) is the environment of the system. A very tractable problem.
>     But then, this division into system and environment must be repeated
>     for the other two bodies in turn, and all the equations must be
>     solved simultaneously.
snip
> Its not
>     that the state-based equations are wrong, but they are limited in
>     what aspects they can model about the three-body system. And if we
>     break the system apart reductionistically, then we lose the
>     /relationship/ of a body pushing on other bodies which push on it.