fixed width navigation, flexible content column

Hi everyone, first post here!

I am putting together a new website for myself at https://www.microcosmologist.com and I have a wordpress blog there. What I want to do is adjust my css style sheet so that the navigation column with all the links on the right side of the page is a fixed width, but the left column, where the blog content is, will scale with the size of the browser window to fill the remaining space. I understand that I can set the width of both columns as fixed pixel sizes (as they are now) but how can I have the right column fixed and the left column rescale with the browser???

Thanks in advance for any help!

JB