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The “Death Cries” of Dark Matter? April 4, 2013

Posted by Will Thomas in Current Affairs.
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The cosmic ray energy spectrum is in the news! The Alpha Magnetic Spectrometer experiment (AMS-02), mounted on the International Space Station, is reporting results about the prevalence of positrons in the cosmic radiation, which otherwise comprises mostly protons. This is being touted as newsworthy, because, if there is a drop-off in that prevalence at higher energies, it will corroborate certain theories of dark matter, which propose that the mutual annihilation of dark-matter particles generates positrons of energies up to but not exceeding levels corresponding to those particles’ high mass.   Similarly enticing results were reported by the PAMELA (Payload for Anti-Matter Matter Exploration and Light-Nuclei Astrophysics) experiment in 2008.  The sophistication of AMS-02 will hopefully be able to take those measurements further, but, unfortunately, we will have to wait a while for more definitive results from higher-energy parts of the spectrum.

The AMS mounted on the International Space Station. Credit: NASA

AMS-02 mounted on the International Space Station. Credit: NASA

What is intriguing about this story is that it really brings us back to where particle physics began over 80 years ago.  In 1930 Robert Millikan (1868-1953), the doyen of physics at the California Institute of Technology, set postdoctoral researcher Carl Anderson (1905-1991) to work on building a cloud chamber in order to measure the same thing AMS-02 is designed to measure, the energy spectrum of cosmic rays.  Millikan believed that measuring the spectrum would confirm his controversial (and incorrect) theory that cosmic rays originated as photons produced in the interstellar synthesis of elements, which then created secondary radiation when they encountered atmospheric nuclei.  Much in the way that every element emits a characteristic spectrum of light, Millikan figured that the energy spectrum of this secondary radiation would cluster into characteristic bands, observing which would, in effect, be like listening to the “birth cries” of the elements.1



Kuhn’s Demon, or: The Iconoclastic Tradition in Science Criticism January 21, 2013

Posted by Will Thomas in Ideology of Science.
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The message that scientists are human and that science is messy is crossing the ether once again. Of late there has been a certain degree of excitement percolating among historians and science-studies scholars over the #OverlyHonestMethods hashtag on Twitter. It seems that scientists are sending out tweets about their work that happen to nicely coincide with the images of science that historians would like to present to the world. Twitter is, of course, the world hub for “trending” topics, and this particular trend is already simmering down. But, before the moment is completely gone, it might be worthwhile to reflect briefly on the history of the ideas 1) that there exists a dominant image of science as a pristine and rigidly ordered activity, and 2) that the negation of this image would be broadly beneficial to scientists and society.


Is it idol-smashing time again already?


Tacit Knowledge and Tactile History: Otto Sibum and “Gestural Knowledge” December 17, 2011

Posted by Will Thomas in Tactile History.
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An 1869 illustration of James Joule's simple, but difficult-to-replicate experiment demonstrating the mechanical equivalent of heat.

This post is the first in a short series on what I call “tactile history”: the practice of historical research that extends beyond examining documents to examining the objects of science and the locations they inhabited, and to the actual reenactment of historical scientific research.  The objective of tactile history is to recover aspects of historical work that would not have survived in the form of a written report.  In this vein, tactile history could be seen as a step beyond “notebook studies” — say, Gerald Holton on Robert Millikan’s oil drop experiments,* or Gerald Geison’s The Private Science of Louis Pasteur (1995) — which look beyond scientific publication to recover the messier day-to-day practices of scientific life.

Where laboratory notebooks merely recover otherwise hidden practices, tactile history attempts to recover something that was never expressed in any form, and is often referred to as “tacit knowledge”.  This could be an inexpressible Fingerspitzengefühl (a fine-tuned hands-on knowledge), a lack of understanding of why an experiment works, pattern recognition, or an unreasoned premonition about what new scientific knowledge will look like.  In the 1980s, tacit knowledge became a crucial part of the “controversy studies” literature, because it was understood to be elemental in successfully replicating an experiment.  By studying controversies surrounding replication, one could uncover the many tacit preconditions underlying successful replication. (more…)