I'm sure you've heard of radiation before - the emission of energy and its transmission through space or matter. When radiation has enough energy, it can break the chemical bonds within molecules and atoms and release particles at very high speed. This is known as ionising radiation and it can be quite nasty to organic life like plants and animals including we humans.
One way to measure radiation (or radioactive decay specifically) is by its half-life - the time it takes for half the energy of some unstable substance to break down and be released as radiation.
The half-life of oxygen is infinity - it is stable and doesn't normally decay.
The half-life of Uranium-238 is nearly 4.5 billion years while the isotopes it decays into, Thorium-230 and Radium-226, have half-lives of 1000's of years - hence the concern about nuclear waste.
And the half-life of Oganesson-293 (first synthisised in 2002) is just 5 milliseconds - half of it decays every 1/200th of a second.
So what does this talk about radiation and half-life have to do with the price of tea in China - or even critical thinking for that matter? Quite a lot actually.
In 1950, there were about 60,000 different academic journals in publication. Today there are over 1,000,000. The amount of new knowledge produced is growing exponentially at roughly 5% per year meaning the amount of new knowledge in the world doubles about every 15 years.
Some of this new knowledge is novel - it concerns things we didn't know about before. But much of it represents the reversal of old knowledge.
Remember Pluto (the celestial body, not the cartoon dog)? When I went to school it was a planet. Now it's not.
Things that we once thought were true, turn out to be not so true after all. And sometimes they even become true again.
The faster new knowledge is created, the faster old knowledge becomes out-dated. This is what has become known as the half-life of knowledge - the time it takes for half of a body of facts to be superseded or found to be untrue.
This phenomenon occurs across all domains of knowledge - from anthropology to zoology and from engineering to psychology. Especially psychology.
Like radioactive decay, we don't know which particular fact (or atom) will decay, and we don't know when a particular fact (or atom) will decay. But we do know how long it will take half of them to decay.
The unfortunate consequence of humanity's rapidly expanding knowledge is this ... most of what you learn over your lifetime will turn out to be wrong.
The average person lives for about 80 years. The half-life of knowledge is about a quarter of that. By the time you die, only a half of a half of a half of a half (less than 7%) of the things that were true at your birth will still be true when you pass away.
Knowledge isn't static. It isn't some eternal collection of facts that can be chiseled into stone. Knowledge is highly dynamic as what is 'true' now will likely change in the future.
Note however that I'm not talking here about some relativistic idea of truth - the daft idea that something real out there in the world might be true for you but not for me, or that opinions are equal to truth.
What I mean when I say that 'truth changes' is that the correspondence between our beliefs and the world outside our minds change. Reality isn't changing (well, not too much anyway!). It is our beliefs about what reality is that changes.
This little philosophical detour into the nature of truth leads us to two important epistemic imperatives (epistemology is the study of knowledge - I'll be talking a lot about this in my free course).
If knowledge has a half-life and that half-life much is less than our own lives, then we need to accept that we will have to change our minds about many things that we hold dear.
We need to accept that we are likely to be wrong about many things and that if we want our beliefs to reflect reality, we must be prepared to change those beliefs.
This can be hard though. Admitting that you are wrong is uncomfortable for most people and impossible for some!
But if you want to be right, if you want your beliefs to reflect reality, then you need to be open to being wrong. A lot.
The only way to deal with this is to adopt the mentality of open mindedness. To (try) be open to new ideas and (try) to be less attached to our current ones.
When the facts change, I change my mind. What will you do?
The other epistemic imperative of the half-life of knowledge is that we need to be skeptical of anything people (including ourselves) claim to be true.
As children, we accept many things at face value. If our parents tell us something is true, we accept it.
As adults, many of us continue to do so. If an expert in a lab coat tells us something is true, we still accept it.
But only some of this knowledge will stand the test of time. We therefore need to subject it to scrutiny and evaluate it for ourselves before accepting it as true.
Now there's an obvious conflict here. We should be open to new ideas but also resistant to them. But there is an easy way to reconcile that conflict -- by embracing the idea of 'maybe'.
Is Pluto a planet? Maybe. But by understanding the competing definitions of different astronomers, we can answer more confidently no.
Are carbs bad for weightloss? Maybe. But by doing meta-analyses on numerous randomised controlled experiments, we can answer more confidently ... maybe.
We need to be open to new ideas but also scrutinise them carefully before accepting them as true.
Because knowledge changes, we should default to skepticisim. We should have good reasons to believe that something is true before we accept it as true.
That's why we should embrace the 'maybe'.
Well ... maybe.
Arbesman, S. (2013). The half-life of facts: Why everything we know has an expiration date. Penguin.
Ioannidis JPA (2005) Why Most Published Research Findings Are False. PLoS Med 2(8): e124.
G'day, I'm Dave!
I work at the intersection of philosophy and technology. I'm a computational philosopher at the University of Queensland where I teach critical thinking, research digital pedagogies, and manage the UQ Critical Thinking Project. When I'm not thinking about thinking, I'm working on becoming a millionaire ski bum.
So far I've nailed the ski bumming bit.