Think of all the things you know. Dinosaurs had brains in their butts and were cold blooded. A lot of your DNA is junk. There are specific brain regions for everything we do. How sure are you of those facts? If they’re more than forty-five years old, you shouldn’t be certain at all. That’s about how long a scientific fact can be considered reliable. Basically, most of what you think you know might be wrong.
Or at least that’s what Samuel Arbesman argues in his book “The Half-Life of Facts: Why Everything We Know Has an Expiration Date.” Here’s what Amazon says about the book:
Facts change all the time. Smoking has gone from doctor recommended to deadly. We used to think the Earth was the center of the universe and that Pluto was a planet. For decades, we were convinced that the brontosaurus was a real dinosaur. In short, what we know about the world is constantly changing.
But it turns out there’s an order to the state of knowledge, an explanation for how we know what we know. Samuel Arbesman is an expert in the field of scientometrics—literally the science of science. Knowledge in most fields evolves systematically and predictably, and this evolution unfolds in a fascinating way that can have a powerful impact on our lives.
How do we know when a fact loses its factiness, and how long can facts survive? Well, Reason says:
Since scientific knowledge is still growing by a factor of ten every 50 years, it should not be surprising that lots of facts people learned in school and universities have been overturned and are now out of date. But at what rate do former facts disappear? Arbesman applies the concept of half-life, the time required for half the atoms of a given amount of a radioactive substance to disintegrate, to the dissolution of facts. For example, the half-life of the radioactive isotope strontium-90 is just over 29 years. Applying the concept of half-life to facts, Arbesman cites research that looked into the decay in the truth of clinical knowledge about cirrhosis and hepatitis. “The half-life of truth was 45 years,” reported the researchers.
This is, in a way, similar to the recent argument made by David McRaney, who wrote the book You Are Not So Smart. Arbesman talks about how what we know changes. But McRaney’s point is that we’re delusional about what we think the world is like anyway. He writes on his site:
The central theme of You Are Not So Smart is that you are unaware of how unaware you are. There is branch of psychology and an old-but-growing body of research with findings that suggest you have little idea why you act or think the way you do. Despite this, you continue to create narratives to explain your own feelings, thoughts, and behaviors, and these narratives – no matter how inaccurate – become the story of your life.
So as Arbesman argues, facts are changing all the time. But McRaney points out that often, even if we know certain things are wrong or, perhaps, have no reason to think they’re right, we still build a narrative to fit them in. Reason puts this well:
People also cling to selected “facts” as a way to justify their beliefs about how the world works. Arbesman notes, “We persist in only adding facts to our personal store of knowledge that jibe with what we already know, rather than assimilate new facts irrespective of how they fit into our worldview.” All too true; confirmation bias is everywhere.
More from Smithsonian.com: