What is ball tampering in cricket and why is Australia captivated by it?

Eight years after then-prime minister Malcolm Turnbull felt the need to weigh in on Australia's ball tampering in the Cape Town Test, sandpaper and cricket are back in the headlines together.Usman Khawaja's book, featuring revelations, allusions and confirmations of what most everyone already believed, has reignited conversations about the Australian team's conduct during that 2018 tour of South Africa.But whatever the team did, who did it and who knew about it, one thing is for sure: they weren't the first to fiddle with the ball.So why did they do it and why was the reaction so extreme?'A beautiful art'Reverse swing can make even the best batters look silly. (Getty Images: Tom Shaw)In the wake of Khawaja's exclusive interview with Nine Newspapers on the weekend, outspoken former Australia fast bowler Geoff Lawson added to the conversation with a brilliantly headlined article."I don't know a bowler who hasn't licked, flicked, scratched or slobbered on a cricket ball."Thanks for those mental images, Geoff.Evocative wording or not, the 46-Test veteran is right. But why?The science of conventionally swinging a cricket ball through the air is relatively simple and adheres to some basic rules of drag, air pressure and laminar flow (a lot of the same stuff that keeps an aeroplane in the air).When a cricket ball is new, its stitched seam is standing at its tallest, allowing a bowler to angle that seam towards or away from the batter and the air will get caught on the seam, dragging the ball in that direction.But the proud seam on a dark red ball is clearly visible to a batter, and the best ones can see what's happening and account for it.Reverse swing is a little more complicated and prized due to it being more difficult to deliver, predict and face.Conventional swing (left) vs reverse swing (right). (ABC News: Gabrielle Flood and Nina Maile Gordon)"As a batter it's the hardest thing to face. It's a beautiful art," former Proteas captain Faf du Plessis told The Grade Cricketer podcast on the eve of Australia's return to Cape Town last month.The ball swings towards the side of the ball that looks smoother due to small abrasions on that "shiny" side of the ball, more of which is facing the batter and therefore offering more surface area and turbulent airflow, this time dragging the ball in the opposite direction to the way the seam is facing.It also happens later in the ball's flight, often too late for the batter to react.It only comes after the ball has been bowled for a few dozen overs and whacked around the field a bit; once the seam has flattened out, and the leather has been, crucially, roughed up and dried out.Weather conditions have to be perfect, the bowlers have to be incredibly skilled and the care for the ball has to be spot-on, to the point that former England captain Alastair Cook was prized as a ball shiner because he barely sweats.Of course, there are other ways to help this along.Spit, sunscreen and swingThere are plenty of legal ways to shine the ball. (Getty Images: Paul Kane)Once a cricket pitch has flattened out from the start of a game, the new ball has lost its shine and proud seam, and before it becomes a spinner's paradise on days four and five (although this is becoming more and more rare), reverse swing is one of the few tools in fast bowler's arsenal.For decades, cricket teams have worked on the ball feverishly to try to work on conventional and reverse swing.Often players will shine the ball on their groin or hip, or use spit or some sweat from their forehead.In those processes, there are some grey areas.Any sensible cricketer will be wearing sunscreen, some will be wearing hair products, many will be chewing gum or chomping on a lolly.Sweat can be used to shine the ball but keeping it dry is key to reverse swing. (Getty Images: Stu Forster)All of that gives a little extra viscosity to the sweat or saliva being used on the ball but, until match referees force players to spit their gum into a hanky on the boundary line or force them to have a shower before entering the field of play, there's not much they can do.Then there's the flip side, where players try to create a rougher surface to generate that turbulent airflow, which can include simple things like picking at the seam of a ball or fielders intentionally throwing the ball in short to ensure it bounces on the coarse pitch block.Ironically enough, du Plessis, South Africa's captain on that fateful 2018 tour, twice stumbled from lightish grey into gun-metal territory earlier in his career.In 2013, after a failed attempt with his fingernails, du Plessis was caught on camera blatantly scratching the ball on the zip of his pants pocket, mere centimetres from legal territory.Teams work hard on the ball to create the conditions for conventional and reverse swing bowling. (Getty Images: Santanu Banik/MB Media)A few years later, as he skippered the team during a 2016 tour of Australia, he was again seen on the field opening his mouth, touching his fingers to a massive white mint on the middle of his tongue, then applying that sugary saliva directly to the ball.Had he simply sucked the mint, popped it into his cheek and then touched his tongue, he could have avoided his own chase through the airport and a hefty fine.Du Plessis described the fallout from his 2013 zipper incident as "a week of hell", so it's no wonder he expressed so much sympathy for Cameron Bancroft and Steve Smith (curiously no mention of David Warner) as the world closed in on them.After massive bans and public disgrace, you would think the world would have moved on, but between the long-awaited Test return to South Africa and now Khawaja's book, the controversy seems never-ending.Why the sandpaper saga?One part absolutely boils to down to Australian cricket's sense of exceptionalism and perception of itself as arbiter of what is and isn't acceptable on a cricket field.But the brazen nature of the ball tampering is perhaps the biggest reason that this was and remains such a big story.England skipper Michael Atherton was caught rubbing dirt into the ball and his reputation remains pristine but, like the various fructose or lotion-enhanced bodily fluids, that's the sort of thing one could use on the ball opportunistically or even inadvertently.Perhaps that's why Bancroft's first feeble attempt at deflection was claiming he "saw an opportunity to potentially use some tape [and] get some granules from the rough patches on the wicket", rather than bringing some 300 grit onto the field where its only purpose could be ball tampering.There are legendary tales of bottle caps being used to help out reverse swing kings like Wasim Akram and Waqar Younis in Test matches way back when, and Khawaja wrote about some of the methods he had seen or heard of in Sheffield Shield cricket.But in a high-profile Test series, to be so obvious when the team knew they already had heat on them betrayed a sense that they thought they were untouchable or that winning was worth the risk.Alas, the SuperSport cameras caught him in high definition and super slow-mo and put the so-called dark arts very much under a spotlight.After du Plessis's minty moment, Dirk Nannes said in commentary at the time for ABC Sport: "It's an art and some of the art is doing it and not getting caught."If that is the case, consider Cameron Bancroft less Gauguin and more Gallagher.