Let $X$ be a linearly ordered topological space with a countable dense subset. Does it necessarily follow that $X$ is metrizable?
A linearly ordered spaceEDIT: Apollo's comment int he answers implies the answer is a setnegative. Let $X$ withbe the open unit interval $(0,1)$ and adjoin to every real number $x$ a total order"ghost number" $x'$ such that $x'$ is the open intervalsimmediate successor of $x$. The "real rationals" are dense in this space. Simply note that sets of the form $(y, x]$ with $x$ and $y$ real and $[x',y)$ with $x'$ ghost and $y$ real form a basis for $X$. For example, every ordinal can be given the order topology and the usual Euclidean topology on thethese sets all contain a real line is the order topologyrational. SeeThis space cannot be metrizable, because the Order topologysubspace topology on Wikipedia. I am not asking for an examplethe set of a separable space thatall ghost reals is not metrizable - there are many examples forexactly that (there's no need forof the Sorgenfrey line, you can even pick the trivial topology...)