There is no doubting the ever expanding reach of science and the acceleration of scientific discovery. Yet the accumulation, and for that matter the acceleration in the accumulation, of ever more knowledge does come with a price — many historical facts that we learned as kids are no longer true. This is especially important in areas such as medical research where new discoveries are constantly making obsolete our previous notions of disease and treatment.

Author Samuel Arbesman, tells us why facts should have an expiration date in his new book, A review of The Half-Life of Facts.

[div class=attrib]From Reason:[end-div]

Dinosaurs were cold-blooded. Vast increases in the money supply produce inflation. Increased K-12 spending and lower pupil/teacher ratios boosts public school student outcomes. Most of the DNA in the human genome is junk. Saccharin causes cancer and a high fiber diet prevents it. Stars cannot be bigger than 150 solar masses. And by the way, what are the ten most populous cities in the United States?

In the past half century, all of the foregoing facts have turned out to be wrong (except perhaps the one about inflation rates). We’ll revisit the ten biggest cities question below. In the modern world facts change all of the time, according to Samuel Arbesman, author of The Half-Life of Facts: Why Everything We Know Has an Expiration Date.

Arbesman, a senior scholar at the Kaufmann Foundation and an expert in scientometrics, looks at how facts are made and remade in the modern world. And since fact-making is speeding up, he worries that most of us don’t keep up to date and base our decisions on facts we dimly remember from school and university classes that turn out to be wrong.

The field of scientometrics – the science of measuring and analyzing science – took off in 1947 when mathematician Derek J. de Solla Price was asked to store a complete set of the Philosophical Transactions of the Royal Society temporarily in his house. He stacked them in order and he noticed that the height of the stacks fit an exponential curve. Price started to analyze all sorts of other kinds of scientific data and concluded in 1960 that scientific knowledge had been growing steadily at a rate of 4.7 percent annually since the 17th century. The upshot was that scientific data was doubling every 15 years.

In 1965, Price exuberantly observed, “All crude measures, however arrived at, show to a first approximation that science increases exponentially, at a compound interest of about 7 percent  per annum, thus doubling in size every 10–15 years, growing by a factor of 10 every half century, and by something like a factor of a million in the 300 years which separate us from the seventeenth-century invention of the scientific paper when the process began.” A 2010 study in the journal Scientometrics looked at data between 1907 and 2007 and concluded that so far the “overall growth rate for science still has been at least 4.7 percent per year.”

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.

In other words, half of what physicians thought they knew about liver diseases was wrong or obsolete 45 years later. As interesting and persuasive as this example is, Arbesman’s book would have been strengthened by more instances drawn from the scientific literature.

Facts are being manufactured all of the time, and, as Arbesman shows, many of them turn out to be wrong. Checking each by each is how the scientific process is supposed work, i.e., experimental results need to be replicated by other researchers. How many of the findings in 845,175 articles published in 2009 and recorded in PubMed, the free online medical database, were actually replicated? Not all that many. In 2011, a disheartening study in Nature reported that a team of researchers over ten years was able to reproduce the results of only six out of 53 landmark papers in preclinical cancer research.

[div class=attrib]Read the entire article after the jump.[end-div]