If it looks like a bubble and acts like a bubble . . .

The old saying, “Better to remain silent and be thought a fool, than to speak and remove all doubt,” is the ever-present curse of the columnist. But what the heck: Bitcoin’s a bubble. There, I’ve said it.

And while I’m at it, it’s not a currency. It’s not an investment, either. At best it’s an invisible, intangible commodity.

Yet everyone from parents at the school gate to hairdressers are talking about the phenomenal growth of a digital creation whose origin cannot be tracked, whose mastermind is unknown and about which we understand less than the origins of life itself.

The blockchain technology that underpins it is brilliant and will likely make future financial transactions faster, more secure and cheaper to execute. There are more than 1 320 crypto-currencies in the world — of which bitcoin is but one.

Bitcoin is emitting the classic signals that suggest it’s a bubble: it took nearly five years for it to move from zero to $1 000 (R13 600), another three and a half to get to $2 000 earlier this year, then it hit $3 000 in 23 days. Two months later it was at $4 000 and took two more to get to $5 000.

Since then, each thousand-dollar increment has taken two weeks or less. It was at $6 000 in eight days, $7 000 13 days later and within 14 days hit $8 000. That’s when the hype went stratospheric.

Nine days later it hit $9 000 and this week, just two days after that, it hit

$10 000, then broke through $11 000 less than 12 hours later, on Wednesday, before beating a hasty 15% retreat. Long-suffering early adopters are paper-rich and stand to realise considerable value if they convert their bitcoin into functional currency. The problem is the late adopters frantically trying to get on the bus.

Why has the price of bitcoin kept going up? Simple: demand.

There is a limited supply of bitcoins and because there is a frenzy to be part of the miraculous growth, oldfashioned greed means that people keep buying because the price keeps going up. Until it doesn’t.

The average real return on bitcoin since 2010 is more than 400% a year. The gains make the dotcom bubble look like child’s play — although the Bank of England this week played down concerns that a bitcoin meltdown could have a contagion effect. It’s just too small.

Bitcoin has all the trappings of the 1700s’ tulip mania in the Netherlands — the subject of a new movie about how ordinary Dutch citizens traded in tulip bulbs. There was no rationale to the frenzied speculation and thousands were ruined when the collapse came.

If you are tempted, you are in good company. Sir Isaac Newton invested — like a great many people — in the 1720s in the South Sea Company, which was granted a monopoly on trade with South America in exchange for assuming England’s war debt. Sensibly, he sold out and pocketed a decent fortune before the shares went stratospheric. He watched his still-invested compatriots becoming ever richer and, weeks before the collapse of the firm, he reinvested — only to see it evaporate before his eyes as the bubble burst. One of the smartest people ever to walk the earth was ruined.

Newton — the guy who identified gravitational force — understood that what goes up must come down.

And still he invested.

Whitfield wishes he’d bought 100 bitcoin at $1 a pop when told to by a richer friend in 2010