Read The Half-Life of Facts for Free Online Page B

half-lives of fields differ. For example, a study of all the papers in the Physical Review journals, a cluster of periodicals that are of great importance to the physics community, found that the half-life in physics is about 10 years. Other researchers have even broken this down by subfield, finding a half-life of 5.1 years in nuclear physics, 6 years for basic solid state physics, 5.4 years in plasma physics, and so forth. In medicine, a urology journal has a half-life of 7.1 years, while plastic and reconstructive surgery is a bit more long-lived, with a half life of 9.3 years (note that this is far shorter than the half-life of 45 years calculated earlier, because we are now looking only at citations, not whether something has actually been disproved or rendered obsolete). Price himself examined journals from different fields and found that the literature turnover is far faster in computer science than psychiatry, which are both much faster than fields in the humanities, such as Civil War history.
    Different types of publications can also have varied half-lives. In 2008, Rong Tang looked at scholarly books in different fields and found the following half-lives.
    Field
Half-life (in years)
Physics
13.07
Economics
9.38
Math
9.17
Psychology
7.15
History
7.13
Religion
8.76
    It seems here that physics has the longest half-life of all the fields examined, at least when it comes to books. This is the opposite of what is found in the realm of articles, where the hardsciences are overturned much more rapidly than the social sciences. This could very well be due to the fact that in the hard sciences only the research that has weathered a bit of scrutiny actually makes it into books.
    Overall, though, it’s clear that some fields are like the radioactive isotopes injected into someone undergoing a PET scan that decay extremely rapidly. Other fields are much more stately, like the radiocarbons, such as carbon-14, used for the scientific dating of ancient artifacts. But overall, these measurements provide a grounding for understanding how scientific facts change around us.
    The story of why facts get overturned—sloppy scientists or something else?—is for chapter 8 , and has to do with how we do science and how things are measured. But shouldn’t the very fact that most scientific knowledge decays be somewhat distressing?
    It’s one thing to be told that a food is healthy one day and a carcinogen the next. But it’s something else entirely to assume that basic tenets of our scientific framework—gravity, genetics, electromagnetism—might very well be wrong and can possibly be part of the half-life of knowledge.
    But this is not the way science works. While portions of our current state of science can be overturned, this occurs only in the service of something much more positive: an approach to scientific truth.
    .   .   .
    IN 1974, three scientists working at the Thermophysical Research Properties Center at Purdue University released a supplement to the
Journal of Physical and Chemical Reference Data
. This was no small undertaking—it was more like an eight-hundred-page book on a single topic: the thermal conductivity of the elements in the periodic table.
    Thermal conductivity refers to how easily each element conducts heat. For example, metals are much better conductors of heat than gases (or plastics) are; that’s why frying pans often have handles made of plastic instead of metal. But in addition to materialshaving different inherent thermal conductivities, there are a number of factors that influence these values. One of the most important is temperature. In general, the hotter something already is, the worse it is at conducting heat.

    Figure 3. Thermal conductivity of copper versus temperature, as derived from multiple experiments. Reprinted with permission from Ho, et al. “Thermal Conductivity of the Elements.”
Journal of Physical and Chemical Reference Data
1, no. 2 (April 1972): 279–421. © 1972,