Subject: What physical laws are used to keep button spinning on string?

I am a homeschool mom of two girls who are ages 11 and 13. I made for them 
an old fashioned toy my grandmother showed me many years ago, where you 
lace a string through a button through both holes, then tie it into a 
continuous loop. Holding the string loop with both hands, with the button 
(about 1 inch or larger) in the center (it will droop down) twirl the 
button by rotating both hands. Then as you gently pull and release the 
string loop ends with both hands, the button spins, and with no limit. It 
makes noise, too. Why is this? Kids would like to describe this at a 
science fair.   

Re: What physical laws are used to keep button spinning on string?