It's somehow far more comforting to hold a couple of crisp fifties in your hands than it is a credit card, because we know they'll allow us to buy enough food, or petrol, or even toilet paper, to tide us over until things get back to normal.

That's why, when the coronavirus hit last year, the Reserve Bank wasn't worried when the number of physical dollar bills in circulation suddenly rose precipitously.

It looked as if people were reacting sensibly, giving themselves a store of cash just in case they needed it. It made sense.

That's the thing about money - it makes perfect sense until, quite suddenly, it doesn't.

Nobody in Australia has had to worry about dollars being worthless.

We don't, unlike Germany, have cultural memory of the 1920s where huge bundles of papiermarks (currency) needed to be transported in wheelbarrows to buy the shopping.

The mark soared from five for a US dollar to 50 at the beginning of 1920 to 100 in '21 to 8,000 in '22 and kept going until, a year later, a loaf of bread cost 200,000-million marks.

There's no inexorable link, of course, but in less than a decade Hitler had taken over and, after the war, Germany's Bundesbank took particular care to guard the currency. Until, of course, the Euro was introduced into circulation in 2002.

Since then we've seen the sort of tensions that were, self-evidently, going to come into play with the currency union rip at the fragile (elite) consensus that were driving the European project.

The problem was that what made sense to a cosmopolitan-knowledge worker in Maastricht wasn't nearly so obvious to a farmer in Greece or engineer in England.

The huge difference was that Greece had abandoned the drachma but Britain still had the pound and that's a big part of the reason why, today, London is outside Europe but Athens isn't.

Money doesn't, by itself, determine the future.

What it does do, however, is provide a means of reflecting the stress of outside events back into the economy.

People need stability and when government's can't provide this (whether because of their own actions or international conditions), trouble follows.

At first glance the countries with inflation problems appear to be mendicant states, like Venezuela (6,500 per cent inflation) and Zimbabwe (350 per cent, down from 680 in the middle of the year).

In Denmark, by contrast, banks are actually charging people who deposit money: a deflationary sign.

Government is attempting to get shoppers out spending and the economy circulating again; but people are less and less interested in the commercial products being offered because they don't believe another, bigger, TV or new, plusher, lounge really will provide the warmth and well-being they're so desperately craving in this time of corona.

It's as if they've looked at all the offerings of the modern world, shrugged their shoulders, and said, "yeah, no, but maybe not after all".

This represents a fundamental challenge to the essence of our economy. People - rich, prosperous, people - are choosing goods that can't be purchased with money.

And then, in the centre of this confusing merry-go-round, with some people who want to get off while others are spinning around, faster and faster at the edges, there's the central pillar, the foundation that's held up the world's economy for so long: the US dollar.

The trouble is, it's showing signs of stress.

Most recently it's been printing money. The US government deficit soared to an enormous $3.1 trillion - tripling in just 12 months. Under Donald Trump it's now occupying a greater share of the economy (15 per cent) than at any time since the end of the Second World War, while the incoming-Biden administration is committed to injecting even more money into the economy. It's like offering a COVID-19 patient oxygen.

Everyone desperately hopes that it will resuscitate them and the patient will recover because there are no alternatives.

There are no guarantees, either, but the point is that the real value we assign to the dollar isn't necessarily there anymore.

The idea behind the economic revolution of floating exchange rates, free trade, and shopping is that it allows us to assign value.

Even if we're still trapped within the broader system at least we're somewhat empowered as when, early in the year, we chose to keep some of our money in cash. It pays to remember this as the fundamentals of the economy are shifting further and further out of line.

Outside the US, Beijing is the biggest owner of greenbacks but it's been stealthily and slowly offloading its reserves.

China faces a catch 22. If the dollar plunges, US goods suddenly become vastly more affordable, its own produce overpriced, and local consumers angry.

That's why it doesn't want a revaluation until its own domestic market can soak up the slack.

Washington, however, doesn't care if its currency has stopped reflecting the real world.

It's effectively managing to offload its deficit and getting other countries to share the pain.

Anyone holding US dollars is sharing in the devaluation of that currency and that's why Danes are paying banks to hold their krone. They believe their government's got its act together more than America or its neighbours in the Eurozone.

There's absolutely no reason that this huge financial edifice will suddenly come tumbling down around us. No reason at all: just as there was no reason that a person eating a bat from a market in Wuhan might have ended up in the deaths of three million Americans or a failed, sub-prime loan in Florida would result in a financial crisis around the world.

The point, however, is that the world is increasingly interconnected and unbalanced.

Our financial system is bearing a burden it might not be able to carry.