&gt; No, it never goes to zero,<p>It never goes to infinity either.  Zero and infinity are the limits.<p>&gt; An infinite number of small numbers adds up to infinity.<p>Well, no.  It depends.  For instance the sum of 1&#x2F;n goes to infinity, but not the sum of 1&#x2F;n².  And since the luminosity of a star decreases with the square of the distance, I incline to believe the sum does converge.<p>But again, that would require some serious, albeit probably not very hard maths.  I&#x27;ve never seen anyone discuss this.  Instead everyone seems to immediately assume the sum would diverge.  That&#x27;s not obvious at all.