[Edu-sig] How do we tell truths that might hurt

[Terry Hancock]

On Saturday 24 April 2004 05:43 pm, Arthur wrote:
> > I'd say it was about as easy, if not easier than writing a
> > function kepler() to solve the (transcendental) inverse of
> > Kepler's equation (solves M = E - e * sin(E) for 'E', i.e.
> > E = kepler(M)). Which was the first real program I ever
> > wrote in FORTRAN (at least the first one that ever compiled).
> > 
> 
> I can't be sure, but I am suspecting that it was Keplers equation which was
> the issue, not the programming to solve it.  If the course requires you -
> courses sometimes do that ;) - to understand Keplers equation, we seem to
> have a home run by knowing enough programming to solve it that way.

No Kepler's equation is not that complicated, it's remembering
the algorithm for inverting the equation, which does something
like "guess an answer, compute the derivative at that point, linearly
project the resulting location of the solution, then use that as the
next guess and so on, until you're within tolerance of the solution".
 
But I've forgotten how to do that in detail.  When I get a break,
I'm probably going to have to go look that up, because I'm a little
embarrassed about not remembering. ;-)

IMHO, that kind of algorithm solving is precisely what math/science
programming is all about.

I was taking orbital mechanics at the time, so the equation was
familiar.

Cheers,
Terry

--
Terry Hancock ( hancock at anansispaceworks.com )
Anansi Spaceworks  http://www.anansispaceworks.com