Thursday, January 3, 2019

The rise of condensed matter physics [Is particle physics over?]

Condensed matter physics, what's that?

Well, think about it. As far as I know, which isn't very far, matter exists in various forms, solid, liguid, gas, and plasma. Which of those would you think of as being condensed (relative to the others).

Solid, certainly, and perhaps liquid, no?

Yes. Condensed matter physics is different from (high-energy) particle physics and cosmology. The physics that shows up in most popular science books is either particle physics or cosmology, you know, quantum mechanics, many universes, strings, bang bangs, black holes and the rest. Old timers like Newton and Galileo aside, that seems to be the public face of physics. But there's more to the discipline than that, a lot more.

But I'm not doing this post to provide my own account to condensed matter physics. I'm writing to call your attention to a recent article in Physics Today, "When condensed-matter physics became king" by Joseph Martin. King starts at the beginning of the 19th century, when it was just one science among others, and quickly brings us to the beginning of the 20th century, when physics had become the preeminent science. Physics had become
“king” in the sense that it came to occupy a central role in Western culture. Physicists marshaled cultural resources—institutional spaces, audiences, patrons, and trust—to create an environment in which their science would become the one most trusted both to probe nature’s secrets and to spawn new technologies.

Similarly, in 1900, when physicists were just beginning to probe the secrets of the atom, the prominence that the physics of complex matter would hold by the turn of the 21st century was scarcely conceivable.
That's the story Martin tells, about the rise of complex matter physics, which is still, alas, more or less invisible to the general public.

I have no intention of summarizing the article, which involves, among other things, the interplay between "pure" and "applied" physics. Rather, I want to leave you with a few paragraphs  from near the end:
In 1972 Anderson published a landmark essay in Science entitled “More Is Different,” in which he argued that each new scale of complexity that scientists engaged with promised a cornucopia of new fundamental and intellectually stimulating questions.13 As condensed-matter physicists tackled more complex physical phenomena, they could therefore expect to open up new intellectual frontiers. Adopting the name condensed-matter physics was more than a simple rebranding. It represented a priority shift driven by changes in both the intellectual and professional circumstances of US physics.

Condensed-matter physicists would test those priorities during the debates that swirled around the Superconducting Super Collider (SSC) in the early 1990s [...]. In what high-energy physicists perceived as an unprecedented act of betrayal, many prominent condensed-matter physicists, including Nobel laureates Anderson and Nicolaas Bloembergen, opposed the SSC—not only in private but also before the policymakers who controlled the project’s fate.

It was a conflict of ideals. For high-energy physicists, the route to fundamental knowledge was a one-way road leading to smaller and smaller length scales. Condensed-matter physicists, who perceived fundamental knowledge at many scales, argued that the funding regime that supported projects like the SSC hamstrung other fields in physics, including and especially their own. As Anderson told Congress in 1989, condensed-matter physics was “caught between the Scylla of the glamorous big science projects … and the Charybdis of programmed research … where you are asked to do very specific pieces of research aimed at some very short-term goal.”

Gripes like Anderson’s were timeworn. Solid-state and condensed-matter physicists had long defended their intellectual worth against charges that they were engaged in Schmutzphysik, or “squalid state physics.” And the concern that big accelerator facilities were vacuuming up funds that might otherwise be dispersed more equitably had been voiced repeatedly since the mid 1960s. But the significant numerical superiority solid-state and condensed-matter physics had enjoyed for decades, combined with the resurgence of its intellectual program, emboldened the field’s leaders. By the late 1980s, condensed-matter physicists were prepared to argue not only that they deserved a place at the core of the discipline but that their aims better represented the aims of physics as a whole than did the parochial interest of high-energy physicists.
Will the CERN Large Hadron Collider turn out to be the last of those big beasts? Is particle physics over, as Sabine Hossenfelder suggests?

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