Non-visual Vistas, Non-spatial Travels

As some of you know, I am currently a graduate student in an experimental condensed matter physics research group. I’m sure that physics graduate school is quite mysterious to people who aren’t in it, and one of my goals for this blog is to explain what I do there and why I choose to do it. I hope my thoughts can be useful to both prospective physics students and to my non-physicist friends and family.

This certainly is a big task, and there’s no chance of me completing it in a single post. Instead, I’d like to start by telling you about the “a-ha moment” when I suddenly realized that condensed matter physics was interesting. It happened on Friday, March 6, 2009, sometime between 3:20 PM and 4:40 PM. It was the spring semester of my sophomore year of college; I was sitting in my thermal physics class, and we were learning about phase diagrams. In particular, my professor showed us the phase diagram for H2O, which I will now show you:

Water Phase Diagram

There is a clear scientific meaning to this picture. Each point on the diagram represents a pressure value and a temperature value; the diagram itself tells us whether H2O will be a solid (ice), liquid (water), or gas (steam) at that particular combination of temperature and pressure. The thick black lines show the locations of phase transitions where H2O changes from one phase to another.

Until this point in my life, I had always felt a sort of impersonal interest in physics. But something suddenly “clicked” when I saw this phase diagram. I had a big realization—that scientific facts really only come alive when interpreted by a human and related back to human experience. I don’t know why this happened. It may have been that I had finally matured enough to realize this, or I may have just needed something special to come along and shake me out of my “scientific stupor.” At any rate, I had an epiphany, which I would now like to share with you.

The first thing to notice is that the phase diagram contains all of our common experiences with H2O. Atmospheric pressure at the surface of the Earth is around 1 bar, which you can find as a horizontal line on the graph. As we travel along this line from low temperature to high temperature, we see that H2O changes from ice to water at 273 K (equivalent to 0°C or 32°F) and from water to steam at 373 K (equivalent to 100°C or 212°F).

Water Phase Transitions at Atmospheric Pressure

The second thing to notice is that the phase diagram contains so much more than all of our common experiences with H2O! People live at pressures near 1 bar and only deal with temperatures between 0-100°C, but H2O exists in a much wider range, and it does many other things besides melt and boil. Let’s discuss three of them:

  1. At low pressures—say, 0.001 bar—water does not exist at any temperature. H2O goes straight from ice to water vapor in a process called sublimation.
  2. There is a single point on the diagram where ice, water, and steam can all coexist. (I marked it with a red dot.) It is located at a pressure of 0.006 bar and a temperature of 0.01°C. Imagine visiting a planet whose atmospheric pressure was 0.006 bar. Water would only exist if the temperature was exactly 0.01°C. If you tried to melt ice, you would find that it simultaneously turned into both water and steam! (The picture below shows solid argon doing this at atmospheric pressure.)
  3. There is another special point where the dividing line between liquid and gas simply disappears. (I marked it with a blue dot.) It is located at a pressure of 221 bar and a temperature of 374°C. At greater temperatures and pressures, there just isn’t a difference between liquid and gas. An interesting consequence of this is that you could turn water into steam without boiling it if you could first raise its pressure to 230 bar, then increase its temperature to 380°C, and finally decrease its pressure back down to 1 bar.

Argon Ice Simultaneously Melting and Sublimating

In one sense, H2O’s phase diagram vividly demonstrates how narrow the human experience is. (Well, it demonstrates one aspect of a much larger narrowness.) We think that ice melts into water, but sometimes it sublimates into steam, and sometimes it does both. We think of water and steam as totally different, but under some circumstances, they aren’t. Living at a single pressure is like always looking in the same direction. Learning about this phase diagram is like suddenly turning your head to the left and right. A whole new vista becomes visible.

In another sense, the diagram shows that even boring everyday substances can become interesting when they’re subjected to unusual conditions. People like to travel because new and different surroundings are fun and exciting; physics teaches us that changing spatial coordinates is not the only way to achieve this effect. Moving to exotic temperatures and pressures is a whole new way to travel.

We can ask a lot of questions about phase diagrams. For example:

  • Do all substances have similar phase diagrams?
  • If not, what changes between substances? Are there certain groups that have similar phase diagrams?
  • Why are different phases stable in different regions?
  • Can we predict the phase diagram for a particular substance?
  • Are there other kinds of phases besides solid, liquid, and gas?
  • Are there other parameters besides temperature and pressure that can change a substance’s phase?
  • Are there different kinds of phase transitions?

Answers to these questions can satisfy out natural curiosity about the physical world and lead to new technological applications. One goal of condensed matter physics is to answer them as fully as possible.

Phase diagrams didn’t point me unambiguously towards condensed matter physics, but they did open my mind to it. They taught me a new way of thinking, and they opened my internal eyes to viewless vistas. Ever since that day in March 2009, I have had a soft spot for them in my “physics heart,” and I hope you can at least partially appreciate why.

References

  • The data for the melting and sublimation lines of water are from “International Equations for the Pressure along the Melting and along the Sublimation Curve for Ordinary Water Substance”, J. Phys. Chem. Ref. Data, Vol 23, No 3, 1994.
  • The data for the boiling line of water are from IAPWS formulation for Industrial Use, 1997.
  • The picture of argon ice is from http://en.wikipedia.org/wiki/File:Argon_ice_1.jpg.

The Two Cultures and a Call for Discussion

When I was a sophomore in college, I took a class about thermodynamics and statistical mechanics. Each chapter of the textbook (An Introduction to Thermal Physics by Daniel V. Schroeder) was preceded by an “amusing” quote about the subject material. One in particular caught my attention; it appeared before the chapter about entropy and the second law of thermodynamics:

“A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists. Once or twice I have been provoked and have asked the company how many of them could describe the Second Law of Thermodynamics. The response was cold: it was also negative. Yet I was asking something which is about the scientific equivalent of Have you read a work of Shakespeare’s?”

This idea fit nicely with some things my friends and I had been talking about, such as the strange fact that many schools offer “science for humanities majors” classes but no corresponding “humanities for science majors” classes. We weren’t interested in taking watered-down humanities courses; we just thought that English majors should have to learn real science. It seemed like a dangerous double standard that could produce one-sided people unable to completely understand the world around them. So naturally, I wanted to read the book that this quote came from: The Two Cultures and the Scientific Revolution, by the British novelist C. P. Snow.

However, the library didn’t have it and my desire to read it quickly got buried under all the other things happening in my life. It’s always been floating around in the back of my head though, and I finally got a chance to read it last month. I can’t say that it quite lived up to my expectations. The book is full of vague generalizations (“If the scientists have the future in their bones, then the traditional culture responds by wishing the future did not exist.”), opinions stated as facts (“The only writer of world class who seems to have had an understanding of the industrial revolution was Ibsen in his old age”), and irrelevant stories about famous people. One of its most serious defects is that Snow never actually explains why a lack of communication between scientists and ‘literary intellectuals’ is bad—he says: “There seems then to be no place where the cultures meet. I am not going to waste time saying that this is a pity. It is much worse than that. Soon I shall come to some practical consequences,” but the consequences never come.

It seems that I am not the only person who was bothered by Snow’s argument (or lack thereof). His book (which was actually the printed version of a public lecture he gave at Cambridge in 1959) set off a huge controversy in the British press. His most famous opponent was F. R. Leavis, a literary critic who in 1962 made a scathing attack (also in the form of a lecture at Cambridge) against Snow and his ideas. Roger Kimball has described Leavis’s talk as “a devastating rhetorical fusillade. It’s not just that no two stones of Snow’s argument are left standing: each and every pebble is pulverized, the fields are salted, and the entire population is sold into slavery.” Leavis’s talk was published as The Two Cultures? The Significance of C. P. Snow, and I read this book too. It’s great—Leavis’s style is unlike anything I’ve ever read, and the cultural issues he brings up seem as relevant today as they did in the sixties.

Four years after his talk, Snow made a response in the form of another book (The Two Cultures: A Second Look, which is usually now included with The Two Cultures and the Scientific Revolution). In it, he expresses his surprise at the controversy he had created. He muses that:

“As the flood of literature mounted, two deductions became self-evident. The first was that if a nerve had been touched almost simultaneously in different intellectual societies, in different parts of the world, the ideas which produced this response couldn’t possibly be original.”

Truer words were never said. The Two Cultures and its surrounding debate are merely the most visible elements in a long string of literature that stretches from the deep past all the way to the present. I have now read quite a bit of it, and it has been a very interesting experience. (See Further Reading for a some of the best/easiest-to-find parts.) All this reading has caused me to think about a number of things that I don’t normally think about, such as:

  • What does it mean to be a scientist?
  • What is and what should be the role of science in society?
  • How does science affect nonscientific beliefs?
  • Is a scientific education sufficient for imparting culture?
  • What would a true synthesis of science and art look like?
  • Is there a “gulf of mutual incomprehension” between the sciences and the humanities? If so, is this bad, and if it is bad, what should be done about it?

And in another sense, I think that all these questions are manifestations of the following deeper questions:

  • How much, and what kinds of things, can humans know?
  • How should one live one’s life?
  • What does it mean to be human?

I think this is the “nerve” that Snow speaks about. I will probably share my thoughts on at least a few of these topics in later blog posts—but I would really like to have a conversation first. So please read some of these things and let me know what you think. If you’re having trouble finding The Two Cultures or The Significance of C. P. Snow, let me know and I may be able to help you out.


Further Reading

The list is virtually endless, so I’ll restrict myself to things available online for free.

  • The Four Ages of Poetry, by Thomas Peacock—a satire of the scientific/anti-poetic attitude the author felt was becoming prevalent. Published 1820. Available here.
  • A Defense of Poetry, by Percy Shelley—a response to Peacock’s satire that explains the virtues of poetry. Written 1821. Available here.
  • Science and Culture, by Thomas Huxley—a lecture given at the opening of a scientific school. His defense of science puts Snow’s to shame. Given 1880. Available here
  • Literature and Science, by Matthew Arnold—a response to Thomas Huxley’s talk. His argument is more effective and less cruel than Leavis’s. It is interesting to note that Arnold and Snow both gave their talks as Rede lectures at Cambridge. Arnold’s is from 1882. Available here.
  • The Value of Science, by Richard Feynman—some philosophy from everyone’s favorite physicist. This is a talk given in 1955. Available here.
  • ‘The Two Cultures’ Today, by Roger Kimball—a look back at the controversy from one of the best social critics around today. Published 1994. Available here.