The half life of facts


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I hate the terminology used. “Facts” don’t have a half-life. Rather, it’s our understanding or explanation of WHY something occurs that changes over time.


And even then, it isn’t like things change wildly with no rhyme or reason. Instead it is mostly minor refinements of existing theories. Decades ago, Isaac Asimov wrote a wonderful essay The Relativity of Wrong on the topic.

Science is wrong about everything, but you can trust it more than anything

This concept is misleading, as there is a tremendous body of science that has been built up and is self consistent. The things that change rapidly are mostly new observations, hypotheses, and theories, or minor refinements to existing knowledge. But they’re still based on the same vast scientific background.

Asimov’s essay is great, and highly recommended. An example he gives is flat earth to spherical earth to oblate spheroid earth to “oblate spheroid plus minor variations north to south” earth. But each refinement was not nearly as major as the previous one. Newtonian physics is still valid in most cases; you have to go to really extreme conditions for relativity to be needed to describe it.

This doesn’t mean that major upheavals won’t come along occasionally.


Remember medicine is a praxis, not a science; it is informed by medical research but that research is ethically constrained pretty severely. So medicine has less factual “facts” than, say, mathematics.


Yeah, I’m not a fan of this framing. (Love the YANNS podcast, though!)

The introductory example in the book is that in 1953 we believed that there were 48 chromosomes in the human genome, and now we know there are only 46. But that doesn’t mean the facts changed.

The statement “there are 46 chromosomes in the human genome” was true in 1953. And it’s true today.

The statement “the best available scientific evidence in 1953 was that there are 48 chromosomes in the human genome, so people believed that” was true in 1953. And it’s true today.

The fact that people didn’t realize that the first statement was a fact in 1953, but did know in 1956, doesn’t change the validity of the statement. It just means they were wrong.

Facts don’t change. The degree to which we know and understand them, and the magnitude of our certainty, does. That’s not the same thing, though.

And the idea of a “half-life” of our beliefs about the facts (not the facts themselves) seems pretty goofy to me. You’d have to stretch any definition of the word “fact” past the point of sensibility for anything remotely like it to be true. I took a lot of physics between 1984 and 1990. If the half-life of physics “facts” is 13 years, only 25% of what I learned about physics should still be regarded as correct. But no, sorry, that’s bullshit. Newtonian mechanics still works as a perfectly good approximation of the motion of physical bodies at non-relativistic speeds. The relativistic corrections we’ve known about since the 1930s still work. We’re learning more about sub-sub-atomic particles and confirming that the weirder things in the Standard Model are actually there, but everything I learned about protons and neutrons and electrons and quarks is still considered correct. Electricity and magnetism aren’t different. Statistical mechanics isn’t different. The Schrodinger and Dirac equations still work, and the experimental support for them is still valid.

So where’s the 75% of what I learned about physics a quarter century ago that isn’t true? There isn’t any.


Very good points. What about the perspective that people perceive “wrong” differently? To one person, a refinement means new information, add it to the heap. To another person, a refinement isn’t additive: it replaces. To still another person, they see a web of interconnected bits with new nodes popping up that were not previously there. If you asked each of them what constitutes being wrong, you might get three wholly different explanations.

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