How to change columns distance? [duplicate]

Possible Duplicate:
Setting the column gap in a twocolumn document

How can I change the distance of two columns in a two-column document?

Here is the internal definition of \twocolumn. In this definition you can see all length which are use.

\def \twocolumn {%
\clearpage
\global\columnwidth\textwidth
\global\divide\columnwidth\tw@
\global\hsize\columnwidth
\global\linewidth\columnwidth
\global\@twocolumntrue
\global\@firstcolumntrue
\col@number \tw@
\@ifnextchar [\@topnewpage\@floatplacement
}


Taken from latex.ltx

You are looking for \columnsep.