Subject: At what rate of passing will Al reflect a magnets field back upon itself?

The other night I was watching "NOVA".  They were talking about bullet trains 
and their magnetic suspension systems.  At one point I recall a man in a lab 
coat turning on a motor which had an aluminum disc attached.  To demonstrate 
what I'm asking about, he had a magnet on the end of a rod which he dropped 
toward the disk.  To my surprise, the magnet bounced like it would have if it 
were aligned in a positive to positive or negative to negative fashion with 
another magnet.  Why didn't I learn about this in grade school?  Why don't we 
see this property demonstrated in other areas of technology?  Wow!!!

Re: At what rate of passing will Al reflect a magnets field back upon itself?