24 августа, 2015 
Pokraskin Two polish’d marbles, . . . by immediate contact stick together
Isaac Newton, Opticks1
Newton was convinced that bodies brought into close contact should adhere strongly. However, the experimental demonstration of this phenomenon was not so readily achieved. Newton reasoned that the imperfection of surfaces was the most important factor inhibiting contact, as described in chapter 1. Therefore he developed better methods for polishing glass lenses to upgrade their quality. This was the work that brought him to famous recognition in 1671 when he first displayed at the Royal society his marvelous new reflecting telescope lenses for improved observation of the stars and planets. However, glass and hard substances like metals are the worst substances for revealing adhesion phenomena. That is why such materials are excellent in ball bearings, which last for years and rarely stick or seize up. So Newton only observed adhesion sporadically. He could not get reliable adhesion between the glass lenses.
It turns out that Newton would have been much more successful in proving his ideas on adhesion if he had used the rubbery material which columbus had brought back from the New World. Such soft material sticks far better than glass. Also, it has become evident that large bodies, like Newton’s glass lenses, are less likely to show adhesion than small ones. If Newton had done his experiments on fine glass fibers, which are easily drawn down from the melt to 10 pm in thickness, five times finer than a human hair, then he would have quickly seen the reliable adhesion he was expecting from his theoretical arguments. The
conclusion is that molecular adhesion is observed best on small, smooth, soft objects. Let us review some of these well-known adhesion phenomena.
Опубликовано в рубрике 