What is the biggest number you can visualise, the biggest that can have meaning for you outside of a calculation in arithmetic?
Thirty-six players on an AFL football field at any one time; that's easy. Their endeavours bring roars from an attendance of perhaps 50,000, twice that number at the end of the season. So you can visualise 100,000, either because you were once part of such a crowd or you were impressed by the television shots of a full MCG.
Now, try to imagine a gathering ten times bigger than that. It is not easy, but perhaps your imagination could stretch to ten full MCGs side by side. More likely, the concept is vague, the image fuzzy. But at least it gives an idea of what we mean by one million.
After that, however, you are doing arithmetic, not forming an image of what ten million or 20 million might actually look like.
Your mind has gone into what computer programmers call overflow.
As for understanding one thousand million — that's 1000 times ten MCGs — forget it. We call that quantity a billion and it is just a number, not an entity that has any real meaning for us, apart from being bigger than a million but smaller than a trillion.
So when we read that the cost of replacing our six submarines with 12 new ones will be $20 billion, it means little to us: it's just a number.
It might as well be $36 billion, which is the figure used by the Australian Strategic Policy Institute for the same work or the $80 billion predicted by the Australian Government in 2014. The Australian Submarine Corporation (ASC) headquartered in South Australia objects to this last figure, estimating that the cost would be between 18 and 24 billion dollars.
"We get cranky when the tax on petrol rises by two cents, but we are quite blasé about billions spent on submarines."
So there you have them, piles of numbers that we can't understand, except that we wonder how one government estimate of the cost to the taxpayer is $80 billion, while a business enterprise owned by the same government prices the work at $18-24 billion.
It is hard to imagine a better example of what happens when overflow affects the human mind, unless you cite the former defence minister who wouldn't trust the aforementioned ASC to build a canoe.
The numbers are just arithmetic symbols with little relevance