Subject: Are the rings in ferrocene constantly rotating?

My textbook says that the rings in ferrorcene are constantly 
rotating, but all of the sources I have looked at indicated that the rings 
are staggered or eclipsed.  How can they be constantly rotating if the 
ring orientation can be known?  Also, according to the references I have 
found, ferrocene has an internal rotation barrier of 4-10kJ/mol. Is this 
barrier just for the change of staggered to eclipsed or is it the barrier 
for the rings to be constantly rotating?

Please include any references used.

Re: Are the rings in ferrocene constantly rotating?