The Half-Life of Facts (6 page)

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 hard
sciences 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 materials
having 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, American Institute of Physics.

This supplement is an exhaustive, data-point-filled text that goes through every chemical element and examines the concept of thermal conductivity. But measuring these curves—trying to determine the relationship between temperature and conductivity for each element—isn’t always that easy. Therefore, they compiled lots of previous research that had gone into measuring these properties and, based on that research, tried to determine what this curve truly is.

By conducting lots and lots of measurements, and seeing where the results fall on the curve, we can begin to realize what the true nature of this thermal conductivity curve actually is for each element. It can be seen in the graph: There’s a lot of noise and uncertainty. But when enough measurements are taken, a really clear picture of how properties are related emerges (in this case, thermal conductivity and temperature). If a certain fraction of the results were removed, or only the results from one of the hundreds of papers cited in the supplement were looked at, there would be a different, less complete, and inaccurate picture of the relationship between thermal conductivity and temperature.

That’s how science proceeds.

It’s not that when a new theory is brought forth, or an older fact is contradicted, what was previously known is simply a waste, and we must start from scratch. Rather, the accumulation of knowledge can then lead us to a fuller and more accurate picture of the world around us.

Isaac Asimov, in a wonderful essay, used the Earth’s curvature to help explain this:

Clearly, when humans went from believing that the Earth was flat to the belief that the Earth was a sphere, there was a
big change in their view. In an entirely unmetaphorical way, the shape of people’s thoughts was changed. But, as Asimov explained, in terms of practical usage, the flat Earth perspective is not that wrong. The assumption of a flat Earth includes the concept of no curvature at all, or zero inches of curvature per mile. Due to boats appearing on the ocean from over a flat horizon, it can be seen that the curvature is not actually zero. But, as Asimov calculates, it’s not that far off. A sphere the size of the Earth has a curvature of only eight inches per mile. That adds up over the size of the Earth, but it’s not that big when you think of it as inches per mile.

An entirely spherical world is not correct either. We in fact exist on a very large object known as an oblate spheroid, which has a curvature that varies between 7.973 and 8.027 inches per mile. Each successive worldview, fact, or theory brings us closer to actually explaining how the world truly works and what the state of our environment is. In the case of the Earth’s curvature, each new theory got us closer to the correct amount that the Earth curves below our feet. Or, in a more complex example, this is similar to how Einstein’s theory subsumed Newton’s results and made them even more general. We can still use Newtonian mechanics for everyday purposes (and, in fact, we almost always do), but Einstein refined our understanding of the world at the edges, such as when we are moving at speeds close to the speed of light.

Sometimes we get things entirely wrong, or not as accurate as we would like. But on the whole, the aggregate collection of scientific knowledge is progressing toward a better understanding of the world around us.

To make this abundantly clear, Sean Carroll, a theoretical physicist at Caltech, wrote a wonderful series on his blog that began with a piece entitled “The Laws Underlying the Physics of Everyday Life Really Are Completely Understood.” While he’s not saying that everything is known about our everyday existence, including the complex notions of “turbulence, consciousness, the gravitational N-body problem, [and] photosynthesis,” what Carroll is arguing is that the fundamental laws that underlie the functioning
of subatomic particles at everyday energies are well-known:

Carroll even lays down, in a single equation, how electrons work in normal, everyday room temperatures. While this is a very general and optimistic example (most of our world is not so easily described by a single equation), this is often how we uncover everything in the environment around us: as part of our pattern of discovery we asymptotically approach the truth. Returning to species, we can see this in action.

In 2010, the Census of Marine Life completed its first decade of work. This project, involving more than two thousand scientists from more than eighty countries, was tasked with chronicling and classifying all living things in the ocean. It involves more than a dozen smaller projects and collaborations with organizations and companies, from NASA to Google.

While they are aware that their work is by no means complete, the team has already produced thousands of scientific papers and discovered well over a thousand new species. A quote from
Science Daily
gives a sense of how unbelievable this is:

Kevin Kelly refers to this sort of distribution as the “long tail of life.” In the media world, a small fraction of movies accounts for the vast amount of success and box office take—these are the blockbusters. The same thing happens on the Internet: a tiny group of Web sites commands most of the world’s attention. In the world of urban development, a handful of cities holds a vast portion of the world’s population. But these superstars aren’t the whole story. While they explain a good fraction of what’s out there, there is a long tail of smaller movies or cities that exist and are still important. Understanding how they are distributed can give us a better picture of how the world consumes popular culture or lives in cities.

So too with species and many other discoveries. As mentioned earlier, when a field is young the discoveries come easily, and they are often the ones that explain a lot of what is going on—or, in the case of species, are the really big ones. Many things that we know about are incredibly common or relatively easy to know; they’re in the main portion of this distribution. But there are uncountably more discoveries, although far rarer, in the tail of this distribution of discovery. As we delve deeper, whether it’s into discovering the diversity of life in the oceans or the shape of the Earth, we begin to truly understand the world around us.

So what we’re really dealing with is the long tail of discovery. Our search for what’s way out at the end of that tail, while it might not be as important or as Earth-shattering as the blockbuster discoveries, can be just as exciting and surprising. Each new little piece can teach us something about what we thought was possible in the world and help us to asymptotically approach a more complete understanding of our surroundings. Whether it’s finding multicellular creatures that can live without oxygen or a shrimp that had been thought dead for sixty million years, both of which
were found by participants in the Census of Marine Life project, each new discovery adds to all that we know about the universe, in its rich complexity and diversity.

.   .   .

THERE
is an order to how science accumulates and explains everything around us that allows us to construct an intricate and ever-improving theory of our world. But just as the science of science can explain how facts are both created and overturned, it can also lead us to understand how other sorts of facts change. And many of these facts are related to the world of technology.

I
had my first experience with the Internet in the early 1990s. I activated our 300-baud modem, allowed it to begin its R2-D2–like hissing and whistling, and began to telnet. A window on our Macintosh’s screen began filling with text and announced our connection to the computers of the local university through this now antiquated protocol. After exploring a series of text menus, I commenced my first download: a text document containing Plato’s
Republic
, via Project Gutenberg. Once I completed this task (no doubt after a significant fraction of an hour), I was ecstatic. I can distinctly remember jumping up and down, celebrating that I had gotten this entire book onto our computer using nothing but the phone lines and a lot of atonal beeping.

It took me almost a decade after this incident to actually get around to reading
The Republic
. By the time I did, the notion that we ever expressed wonder at such a mundane activity as downloading a text document seemed quaint. In 2012, people stream movies onto their computers nightly without praising the modem gods. We have gone from the days of early Web pages, with their garish backgrounds and blinking text, to slick interactive sites using cascading style sheets, JavaScript, and so many other bells and whistles that make the entire experience smooth and multimedia-based. No one thinks any longer about modems or the details of
bandwidth speeds. And certainly no one uses the word
baud
anymore.