无法在VPyhton (GlowScript)中添加标量和矢量错误

Question

我正在用VPython在GlowScript中实现一个太阳系。现在，我在运行时收到了这个错误: error不能添加标量和向量。我想我做得很对。我需要用pos换点东西吗。？

以下是代码：

GlowScript 2.7 VPython
from visual import *

scene = display(width = 800, height = 800, center = vec(0,0.5,0))

#sun
sonne = sphere(pos = vec (0,0,0), radius=8, color = color.orange, shininess=1)

#earth
erde = sphere(pos = vec (50,0,0), radius=1.5, color = color.blue, make_trail=True)

erdeV = vector(0,0,5)

#masses
erdeM = 5.97*10**24
sonneM = 1.989*10**30

#Grav-constant
G = 6.67259*10**-11

for i in range (1000):
    rate(1000)
    erde.pos = erde.pos + erdeV

    #distance
    entfernung = sqrt(erde.pos.y**2 + erde.pos.z**2)


    #Gravitational law F = G * m * M / r*r --> G*s*e/AE*AE ae=Astr. Einheit
    Fgrav = G *( erdeM * sonneM) / (entfernung*entfernung)
    erdeV = erdeV + Fgrav
    erde.pos += erdeV

    if entfernung <= sonne.radius: break

Answer 1

问题线：

Fgrav = G *( erdeM * sonneM) / (entfernung*entfernung)
erdeV = erdeV + Fgrav

Fgrav这里是一个标量(引力强度)，而erdeV是一个矢量。为纠正这一情况，应包括部队的方向：

Fgrav = (-G * (erdeM * sonneM) / (entfernung ** 3)) * erde.pos
erdeV = erdeV + Fgrav