do we need to recompile libraries with c++11?

Question

This is a very uninformed question, but:

I would like to start using C++11. Can I continue to use my large collection of libraries which were compiled with my old gcc 4.2.1 compiler or do I need to recompile them all with a new compiler? I would think (or hope) the answer is no, but I am only a dabbler.

So that I may have at least part of my ignorance removed, can you explain why in either case?

Thanks