Is there a reasonable way to use numbers smaller than about 10^-6

Geoff Canyon gcanyon at gmail.com
Wed Nov 20 21:48:00 EST 2013


Sure -- note that I'm not solving the 3-body or N-body problem. I'm going
moment to moment, calculating the gravitational effects at that time and
applying them. I'm inherently inaccurate because I'm only checking every
<time-unit> which for long trips could be hours. The math to do this is
fairly simple, actually, but as I've said previously, I've confirmed my
results using Kepler's 2nd law.


On Wed, Nov 20, 2013 at 3:01 PM, Roger Guay <irog at mac.com> wrote:

> Wow Geoff, this is very impressive! I tried to do similar simulations of
> this kind in the past, but failed. At the time, I chalked it up to the
> complexities of the "3-body problem" and set it aside. I’ll be very anxious
> to hear about your progress. Please keep me/us posted, if you will.
>
> Thanks,
>
> Roger
>
>
> On Nov 20, 2013, at 11:37 AM, Geoff Canyon <gcanyon at gmail.com> wrote:
>
> > It's not a secret. I posted about a month ago in fair detail, but I'm
> doing
> > a space simulation, similar to Kerbal Space Program or Simple Rockets,
> but
> > with correct gravity (they both take shortcuts that appall me). I just
> > found out that the Animation Engine has a 3D projection function, so if
> > that tests out I'm going to switch from 2D to 3D. The end result should
> be
> > fairly simple visually, but with an accurate representation of every
> round
> > body in our solar system (about 50) all of them applying gravity
> correctly
> > and simultaneously to the rocket(s).
> >
> > So far I have correct 2D gravity, export/import of universe definitions,
> > multiple simultaneous rockets, landing, taking off, and crashing. The
> > planets and moons run on set paths (I don't calculate their gravitational
> > interactions with each other). I need to at least change the paths from
> > circles to ellipses, or let them run freely. I need to finish converting
> to
> > km/s/kg from the abstract numbers I started with. I need to add
> atmosphere.
> > I need to real-ify the rockets (currently they are one-stage, crazy
> > powerful, and have unlimited fuel). And if I'm lucky, convert to 3D. And
> > start testing on an iPad (the eventual target).
> >
> > And I will just say, orbits are hard.
> >
> > gc
> >
> >
> > On Wed, Nov 20, 2013 at 12:28 PM, Roger Guay <irog at mac.com> wrote:
> >
> >> This sounds very interesting, Geoff. Sure would like to know what you’re
> >> up to….
> >>
> >> Roger
> >>
> >>
> >> On Nov 20, 2013, at 10:21 AM, Geoff Canyon <gcanyon at gmail.com> wrote:
> >>
> >>> On Wed, Nov 20, 2013 at 10:53 AM, Richmond <
> richmondmathewson at gmail.com
> >>> wrote:
> >>>
> >>>>
> >>>> Ordinary math seems to peter out at 0.000001.
> >>>>>
> >>>>> This puts 8.100e-13: put format("%1.3e", (1e0)/(1234567890123e0))
> >>>>>
> >>>>> So is something like that the best way to go?
> >>>>>
> >>>>
> >>> My plan so far is just to do the math. If the result is 0, then
> increase
> >> my
> >>> timescale by 100,000 and try again. (and repeat as necessary) That way
> >> when
> >>> there is something overwhelming nearby, extremely distant/small objects
> >>> will have 0 effect, but if there is nothing nearby/large, then
> >>> smaller/farther objects will be applied across timescales that work for
> >>> them.
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