Can the following construction be used to measure countable sets?

Solution 1:

I found a counter-example to the credibility of my measure that I should have found a long time ago. If we set $T_1=\left\{\left.\frac{m}{2n+1}\right|m,n \in \mathbb{Z}\right\}$ and $T_2=\left\{\left.\frac{v}{4r+2}\right|v,r\in\mathbb{Z} \right\}$, then according to my measure, $\mu(T_1)=\frac{2}{3}$ and $\mu(T_2)=1/3$.

However, if we change $T_1$ into $\left\{\left.\frac{2m}{4n+2}\right|m,n \in \mathbb{Z}\right\}$ we find that $T_1 \subset T_2$. Hence for my measure to have some credibility $\mu(T_1)<\mu(T_2)$. Morover $T_1$ had to be non-reduced to be comapared to $T_2$, which goes against my argument of simplification.

Hence, my measure cannot be used.

Hoefully someday there will be a measure that can be applied to any countable dense set.