= Gravitational field null between two point masses
{title2=$x=D/(1+\sqrt{M_2/M_1})$}
Two positive <point masses> $M_1,M_2$ separated by $D$ have a unique intervening <gravitational field> zero. At distance $x$ from $M_1$, <Newton's law of universal gravitation> gives $M_1/x^2=M_2/(D-x)^2$, hence the displayed value. The signed offset towards $M_2$ from their <centre of mass> is $x-DM_2/(M_1+M_2)$. This instantaneous cancellation is distinct from a <Lagrange point>, which includes the <centrifugal force> of a co-rotating description. Along the joining line the zero is unstable: the derivative of the signed <acceleration> is $2GM_1/x^3+2GM_2/(D-x)^3>0$.
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