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

Roger Guay irog at mac.com
Thu Nov 21 04:42:20 CET 2013


As you describe it, I think I was attempting to do the same thing. I’m still impressed!!

Thanks for taking the time to describe your project.

Roger


On Nov 20, 2013, at 6:48 PM, Geoff Canyon <gcanyon at gmail.com> wrote:

> 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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