Half of what you know is wrong — according to Science

Adam Walker
3 min readFeb 14, 2020

We tend to think of facts like concrete, a solid foundation. They aren’t. Facts are fluid because our knowledge is always growing and expanding.

Man climbing a ladder
Photo by Jason Wong on Unsplash

Facts change

“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.”

The Half-Life of Facts: Why Everything We Know Has an Expiration Date by Samuel Arbesman

Arbesman’s book goes on to talk about how facts have a half-life. Half-life is the time it takes something to decay by half. The Oxford Dictionary says a half-life is the time taken for the radioactivity of a specified isotope to fall to half its original value. For our context, the half-life of facts is the time it takes for half of the facts we know to be updated with better information or proven entirely inaccurate.

It turns out that in some areas, even in the medical field, facts have a half-life of around 45 years. Here’s how Arbesman puts it.

“Furthermore, they got a clear measurement of the half-life of facts in these fields by looking at where the curve crosses 50 percent on this chart: 45 years. Essentially, information is like radioactive material: Medical knowledge about cirrhosis or hepatitis takes about forty-five years for half of it to be disproven or become out-of-date.”

If facts change, what do we do?

What do we do with this information? If facts aren’t stable, what is? The solution is learning. If our foundation is learning, we will always be standing on the best information, and using the most current and accurate facts as our foundation.

Having facts as a foundation is fine, as long as we are willing to update parts of the foundation that decay. Like an old basement has to be reinforced from time to time to maintain the stability of a house, our facts must be reinforced and sometimes swapped out to maintain stability in our lives. If we are continuously learning, we are updating our facts (that are decaying), and gaining a new understanding that helps us to make sense of the world.



Adam Walker

Husband. Father of six. Wearer of fedoras. Serial entrepreneur. Nonprofit co-founder. I write about personal growth & leadership.