Re: Processcycledonation and n-Body-problem

Amara Graps (
Fri, 19 Sep 1997 23:38:35 -0800

>Mikael Johansson wrote:
>> I've had a discussion with my maths-teacher about a gravityproblem in
>> association with the n-body-problem, and my question is this:
>> The n-body-problem is unsolvable due to the gigantic computing powers it
>> would take just for three interacting bodys, right?

>Not at all. Any computer can easily simulate N gravitationally interacting
>bodies using N^2 cycles. My computer could easily handle a thousand-body problem.

>The n-body-problem is "unsolvable" because the only way to get an answer is
>through an actual simulation. With other problems, you can plug time 't' into
>some equation and calculate the result directly.

I think he was asking if an nbody problem can be solved analytically.
I guess I am rephrasing you. So the answer is no, you cannot solve
it analytically. You can solve it numerically, though.

You may be interested in my nbody page. Researchers who do this
sort of thing professionally in the last 20 years have come with
a number of methods to perform nbody simulations. Those methods
approach O(n) in some cases.

And I wrote up something a couple of years ago in response to
a newsgroup question about the 3 body problem.

The restricted 3-body problem can be solved analytically, but the
general 3-body problem cannot. It really amazing how quickly one loses the
ability to solve these sorts of gravitational problems analytically.


Amara Graps email:
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