This is a tale of three money pits. It's also a tale of monetary regress — of the strange determination of many people to turn the clock back on centuries of progress.
The first money pit is an actual pit — the Porgera open-pit gold mine in Papua New Guinea, one of the world's top producers. The mine has a terrible reputation for both human rights abuses (rapes, beatings and killings by security personnel) and environmental damage (vast quantities of potentially toxic tailings dumped into a nearby river). But gold prices, while down from their recent peak, are still three times what they were a decade ago, so dig they must.
The second money pit is a lot stranger: the Bitcoin mine in Reykjanesbaer, Iceland. Bitcoin is a digital currency that has value because . . . well, it's hard to say exactly why, but for the time being at least people are willing to buy it because they believe other people will be willing to buy it. It is, by design, a kind of virtual gold. And like gold, it can be mined: you can create new bitcoins, but only by solving very complex mathematical problems that require both a lot of computing power and a lot of electricity to run the computers.
Hence the location in Iceland, which has cheap electricity from hydropower and an abundance of cold air to cool those furiously churning machines. Even so, a lot of real resources are being used to create virtual objects with no clear use.
The third money pit is hypothetical. Back in 1936 the economist John Maynard Keynes argued that increased government spending was needed to restore full employment. But then, as now, there was strong political resistance to any such proposal. So Keynes whimsically suggested an alternative: have the government bury bottles full of cash in disused coal mines, and let the private sector spend its own money to dig the cash back up. It would be better, he agreed, to have the government build roads, ports and other useful things — but even perfectly useless spending would give the economy a much-needed boost.