Ball Tampering – "unlawful alteration of the surface or seam of a ball on the field, to affect its motion when bowled."
Cricket is a batsman’s game. Over the course of last one and a half centuries, laws of the game have been tweaked to make it “swing” increasingly in the batsmen’s favour. Covered pitches, restrictions on bowling, restrictions on field placements, shortened boundaries, better safety equipment, bigger bats, and changes in the front-foot no-ball rule. Almost every single rule change tilting the balance further in the batsmen’s favour.
Meanwhile, the bowlers have also lived up to the ask, with constant innovations, Bodyline, Swing, spin, chinaman, doosra, reverse swing, knuckle ball, carom ball et al. In due course some have even resorted to the dark arts as well.
The cricket ball, like everything else on this planet, follows the laws of physics. Bernoulli’s principles regarding motion through a fluid holds especially true. Although, no one has worked out the exact calculations or made big differential equations on the subject, it can be safely said, the more the difference in the nature of the two halves of the ball, the more its tendency to swing. So ensure that one side stays as smooth as possible while other side stays as shiny as possible. Although keep in mind, that is one of the many variables affecting the swing. Others being speed of release, angle of the seam, ambient temperature, wind etc. However, while other variables are not exactly in control, the shape of the ball can be “managed” in multiple ways. Some legal, some illegal, and many falling in the grey area. It is certainly an art, although there are some who move into the darker arts.
Below is a pictorial representation of the different techniques to manage the shape of the ball.
Use of any visible agent to change the shape certainly falls in the definitely illegal category. And that is what Cameron Bancroft was caught doing against South Africa. Caught on the cameras with a piece of sandpaper in his pocket which he then tried to hide in his pants post instructions from dressing room, all of which caught by the South African cameramen who were specifically assigned to the task of catching any Australian transgressions. Post the day’s play, Steve Smith admitted to the leadership group’s involvement in the shenanigans. Next day, Tim Paine was leading the side with both Smith and David Warner having resigned in the middle of the Test!