Interior of Singleton in Real Number Line is Empty

Theorem
Let $\left({\R, \tau_d}\right)$ be the real number line under the usual (Euclidean) topology.

Let $a \in \R$ be a real number.

Then:
 * $\left\{{a}\right\}^- = \varnothing$

where $\left\{{a}\right\}^-$ denotes the closure of $\left\{{a}\right\}$ in $\R$.