Nothing more than this year's best guess

 Don’t panic, but everything you think you know could be wrong. Sit down and let Russ Swan hold your hand through this difficult realisation…

 DO YOU know something? In fact, do you know anything? Well of course you do – you're an educated person with an interest in science and excellent taste in reading matter, or you wouldn’t be here in the first place. You probably know quite a few things.

The whole point of science, of course, is to learn things. It's what we do, routinely. Find stuff out. Overturn outdated ideas and replace them with shiny new ones. Make progress.

But most of what we know, we don't know because we discovered it. We were told it by people we trust – the authors of books, university lecturers, work colleagues.

We can't start from first principles each time, or we'd never get beyond banging two stones together. Even the great Isaac Newton credited the remarkable progress he made to those that came before: "If I have seen farther it is by standing on the shoulders of giants".

This is a perfectly sensible way to go about life. But what if everything you think you know turns out to be wrong? We're used to the idea that scientific knowledge is in a constant state of flux, that what we currently consider to be fact may one day turn out to be fiction. This is normal, and probably more normal to a scientist than the average human on the Clapham omnibus.

What seems less normal is the rate at which facts are now being overturned. We live in a golden age of scientific discovery, and I doubt if there has ever been a time in history when so many facts were so eagerly overturned by so many.

I don’t know about you, but I fear that my personal flux capacitors are approaching overload.

What colour is the planet Mars? Everyone knows that it is red. You can see it through a telescope, and you can look at pictures beamed back from the rovers. And yet, earlier this year, Nasa scientists were reportedly 'astonished' to see that a rock driven over by Curiosity rover had snapped in two and was actually white inside.

I'm not sure why they were astonished, because it has been obvious for some time that Mars is not red at all. It's just a bit dusty. Tracks left by the rovers have exposed various colours beneath, and when rocks have been swept for closer inspection or drilling they have shown a range of hues. To call Mars red would be to call my car beige (it's black, but like the fourth rock from the sun would really benefit from a good wash).

This is just one example of the tsunami of fact-overturning that has beset us. Last month I read a paper that solemnly declared that osmosis is not the result of any tendency of solutes to dilute water, despite the inescapable fact that I once got a distinction for an undergraduate paper which said more or less that. Is nothing sacred?

The overturning of established belief has spawned a whole new industry, which exists only to point out how wrong we all are about everything. This new profession of cleverdickery takes delight in identifying and exploding myths, especially those thought of as common knowledge.

At the head of this new guild of Smart Alecs is of course Stephen Fry, host of the long-running panel show QI. He is joined by a growing legion of authors, bloggers, and presenters who make their living trying not to sound too smug when correcting our universal stupidity.

But as well as an industry, this phenomenon has also sparked a new science, with its own peer-reviewed journal and everything.  Scientometrics is the science of measuring science, and provides some fascinating metadata on why a large part of what you think you know is wrong. Bear with me on this, because it's not as soft as it might first appear.

We're used to the idea of financial inflation, which means for example that an average annual rate of 7% leads to a doubling of prices in ten years. Knowledge is estimated to be inflating slightly more slowly, at about 4.7% per year (according to a 2010 study of a century of published data in the journal Scientometrics). This gives a doubling of knowledge every 15 years or so.

Some of this is new knowledge, and some of it overturns old, and the sums can be reconciled by a concept that scientometrics advocate Samuel Arbesman describes as the half-life of facts. This, he reckons, is about 45 years.

In other words, if you graduate at age 21 and retire at 66, just about half of what you think you know about everything will be wrong – or would be if you hadn’t re-learned along the way.

This is both exciting and terrifying, and neatly reinforces my own belief that scientific fact is nothing more than this year's best guess. The good news is that it should keep us all in work for the foreseeable future.