eToys surprises
hjh-sqlist at lexdb.net
hjh-sqlist at lexdb.net
Fri Dec 24 09:03:52 UTC 2004
Hi
The Newtonian orbits screen is impressive. I'd like to learn how that is done.
I see that now variables are possible in eToys. The last time I looked into
eToys (some time ago..) this wasn't possible. Is there a tutorial or a short
movie which shows how to use them? How do I define them?
On http://www.squeakland.org/author/etoys.html in particular (e.g. quickstart
guide) I do not see anything like that.
Hannes
Quoting Alan Kay <alan.kay at squeakland.org>:
> It is also very easy to do Newtonian orbits in etoys, if full precision is
> used for acc, vel, and position properties. The script looks just as one
> would like: do this in a playfield with origin at center, place the sun
> there, and the vector distance of the earth is also its distance to the
> sun. It's not science to claim inverse square, but it's one of the
> plausible hypotheses with an analogy to the intensity of light. Newton
> actually proved his stuff as math long before he got to the last books
> where he looked to see how the phenomena in the world behaved. Given this
> as an hypothesis, the script is straightforward: the strength of the force
> being inversely proportional to the square of the distance, and the
> direction of the accelleration is the opposite direction of the vector that
> is the Earth.
>
> Cheers,
>
> Alan
>
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