# Why solid angle of a closed surface from exterior is zero?

Actually my question comes from Gauss law which says charges outside a closed surface, doesn't effect on the whole electric flux of the surface.

The reason of that is that the solid angle of a closed surface while measuring it from outside of the surface, is zero. ( on the other hand, the solid angle of a closed surface from inside the closed surface is $4\pi$)

My question is why solid angle of a closed surface from exterior is zero? Please don't use Stokes' theorem!

• Please don't put the question only in the title, but repeat it in the body and elaborate on it. It is currently unclear what you're asking - what do you mean by "solid angle of a surface", and what has Gauß' law to do with it being zero outside the surface? – ACuriousMind Apr 25 '17 at 10:49
• Sir, I meant that we can talk about Gauss law by using this fact, which the solid angle of a closed surface is zero when you are measuring it from outside of it. – David 2000 Apr 25 '17 at 12:58