Subject: Wondering about quantum entanglement...

I learned of a property of quantum mechanics, "quantum entanglement," where 
two photons that have split off from a single photon will have properties 
that are correlated with each other, so even if the photons are separated 
by light-years, knowing the properties of one immediately reveals the 
properties of the other, bypassing the restriction that no information can 
travel faster that the speed of light.  But I don't understand how this is 
essentially different from someone taking two cards, for instance, and 
puting them in two separate envelopes, mixing the two so that no one know 
which card is in which envelope, and sending them to each end of the 
country, then opening one envelope and seeing the card will immediately 
reveal which card is in the other envelope at the other end of the country. 
 So the correlation of properties of two distant objects need have nothing 
to do with quantum mechanics.  The question is what's the difference 
between these two cases?
Thanks.

Re: Wondering about quantum entanglement...