太陽能系統模型Python - 列表操作難度

Question

這是我在這裏的第一篇文章。 所以我正在嘗試使用visual python製作模型太陽系。我將每個行星定義爲一個球體，具有半徑，與太陽，質量和動量變量的距離。然後將每個行星（或身體）放入列表結構中。正如你目前所看到的，我有一份[地球，月亮，火星]的名單，因爲我不久將解釋太陽被排除在外。

所以我的問題來了，當我試圖計算每個身體對每個其他身體造成的力量。我在這裏所做的是，對於身體列表中的每一個第i個值，計算它與第n個身體之間的力量，列舉身體中第i個身體的力量是第i個身體與第n個身體之間的力的總和body從0到列表的末尾。 （即列表中所有其他物體的所有力的總和）

這適用於月球和火星（列表中的第二和第三項），但不適用於地球。下面的代碼的輸出是，

<3.57799e+022, 0, 0> 
<4.3606e+020, 0, 0> 
<1.64681e+021, 0, 0> 
<-1.#IND, -1.#IND, -1.#IND> - this is the total force on earth. 
<0, 2.07621e+027, 0> 
<0, 9.83372e+027, 0> 



from visual import * 


AU = 149.6e9 
MU = 384.4e6 # moon - earth orbital - radius 
MarU = 227.92e9 

G =6.673e-11 

sun_mass =2e30 
sun_radius =6.96e8 
earth_mass =6e24 
earth_radius =6.37e6 
moon_mass =7.35e22 
moon_radius =1.74e6 
mars_mass = 6.41e23 
mars_radius = 3390000 
sun = sphere (pos =(0 , 0 ,0) , velocity = vector (0 ,0 ,0) ,mass = sun_mass , radius =0.1* AU , color = color . yellow) 
earth = sphere (pos =(AU , 0 ,0) ,mass = earth_mass , radius =63170000, color = color . cyan ,make_trail=True)# create a list of gravitating objects 
moon = sphere (pos =(AU+MU , 0 ,0) ,mass = moon_mass , radius =17380000 , color = color . white, make_trail=True) 
mars = sphere (pos =(MarU , 0 ,0) ,mass = mars_mass , radius = mars_radius , color = color . red, make_trail=True) 

#initialise values: 
we = 1.9578877e-7 
wm = sqrt(G*earth.mass/3.38e8**3) 
wma = 9.617e-5 
dt = 3*60 

earth.mom = vector(0,1.5e11*earth.mass*we,0) 
mars.mom = vector(0, 9.833720638948e+27,0) 
moon.mom = moon.mass*(earth.mom/earth.mass+vector(0,-3.48e8*wm,0)) 

bodies = [earth, moon, mars] 

*N = 0 
initialdiff = 0 
for i in bodies: 
     initialdiff = i.pos - sun.pos 
     TotalForce = (G * i. mass * sun. mass * norm (initialdiff)/ initialdiff . mag2) 
     print TotalForce 
     while N < len(bodies): 
      if N!=i: 
       diff = i.pos - bodies[N].pos 
       Force = (G * i. mass * bodies[N]. mass * norm (diff)/ diff . mag2) 
       TotalForce = TotalForce + Force 
       i.mom = i.mom+TotalForce*dt 
       N = N+1 
      else: 
       N = N+1 
print earth.mom 
print moon.mom 
print mars.mom* 

感謝您的任何幫助，你可以給。

Answer 1

'''Abel Tilahun HW 3 ''' 

# 02/03/2015 

# make the necessary imports , visual import gives visual output, cos, sin and pi allows calculation of the positions 
# in real time. The numpy arange import returns evenly spaced values within a given interval (angles) 

from visual import * 

from math import cos,sin,pi 

from numpy import arange 

# i used 'a' to magnify the sizes of the planet for better visualization 
a=600 

# the following line defines a sphere for the sun centered at the origin(0,0,0) all the other planets are positioned at a radial distance from this center. 
Sun=sphere(pos=(0,0,0),radius=6955500*(a/100),color=color.yellow) 

#the next 5 commands code the planets with their center being positioned at a distance of the radii of their orbit. Their radii are multiplied by a factor of 'a' to magnify them 

Mercury=sphere(pos=vector(579e5,0,0),radius=2440*(a),color=color.red) 

Venus=sphere(pos=vector(1082e5,0,0),radius=6052*a,color=color.orange) 

Earth=sphere(pos=vector(1496e5,0,0),radius=6371*a,color=color.green) 

Mars=sphere(pos=vector(2279e5,0,0),radius=3386*a,color=color.white) 

Jupiter=sphere(pos=vector(7785e5,0,0),radius=69173*(a),color=color.cyan) 

Saturn=sphere(pos=[14334e5,0,0],radius=57316*(a),color=color.magenta) 

# the for loop calculates position of the planets by changing 
# the arange function increases the angle from 0 to pi with a small increment of 0.025 each time 

for theta in arange(0,100*pi,0.025): 

    rate(30) 

    x = 579e5*cos(theta) 

    y = 579e5*sin(theta) 

    Mercury.pos = [x,y,0] 


    x = 1082e5*cos(theta) 

    y = 1082e5*sin(theta) 

    Venus.pos = [x,y,0] 


    x = 1496e5*cos(theta) 

    y = 1496e5*sin(theta) 

    Earth.pos = [x,y,0] 


    x = 2279e5*cos(theta) 

    y = 2279e5*sin(theta) 

    Mars.pos = [x,y,0] 


    x = 7785e5*cos(theta) 

    y = 7785e5*sin(theta) 

    Jupiter.pos = [x,y,0] 


    x = 14334e5*cos(theta) 

    y = 14334e5*sin(theta) 

    Saturn.pos = [x,y,0]