The Simple Addition Of A Hankerchief Makes A Cup Become Heavy

I've noticed that with the passing of years, gravity seems to become stronger somehow. Here's a reminder of the gravitational pull's tendency to challenge our expectations. A plastic cup is placed on a flat surface such as a book, and is easily lifted from the book in the normal fashion. However, upon the introduction of a flimsy hankerchief which is placed inside the cup, the act of lifting it from the book appears impossible. Indeed, the book and cup can be turned upside down, and still the cup remains on the book. Finally the hankerchief is removed and the cup once again becomes compliant.