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Robert Jaffe: Academics, Activism, and Armageddon

Professor Robert Jaffe Speaks On Activism and Black Holes

By Erik Snowberg

Professor Robert Jaffe is the director of the Center of Theoretical Physics at MIT. He has served as chair of the faculty and is a MacVicar Fellow. On July 30th I interviewed him in his office about campus activism and his latest efforts to make the world safe for humanity. This interview is available in RealVideo format at The Tech’s website. <>

The Tech: I noticed on your curriculum vitae that you are on the advisory board of the Office of Minority Education and a member of the Campus Committee on Race Relations. How did you get involved with those organizations?

Jaffe: My roots in issues of campus life and educational policy go way back to when I was a graduate student. I was involved at Stanford in setting up program called the Stanford Workshops on Political and Social Issues. It tried to use the academic environment to help students to solve social problems. I brought that with me when I got involved with MIT politics the first year I was chair of the faculty, in response to some racial incidents on campus involving some people shouting slurs out of the windows of fraternities.

There was a group meeting which was trying to figure out a way to improve racial dialogues on campus. That group eventually turned into the race relations committee. My role in that group was trying to engage faculty in the committee, and now it does have a fairly good faculty component.

The Tech: Tell me more about the Stanford Workshops. How did it relate to your graduate education?

Jaffe: Theoretical physics is quite abstract. I don't think you can construct a rational chain that leads from theoretical physics to some political, social or educational imperative. I think people who are in physics often take on other projects in their life that look disjoint but are just part of an educational life.

When I was a student there were two things that were unusual compared to today. The first thing was the level of anxiety in the society about what was happening because it was during the Vietnam War.

The second was the level of empowerment that students felt. The ability of students to take things on their own and use institutions to create something new without asking permission was different than it is today.

A group of us discovered that Stanford had a loop-hole in its rules for granting credit which said that any faculty member could offer a one-half credit course just by signing off on it. They were called faculty seminars.

We discovered that we could get our friends who were concerned about American society and the war to sign off as the faculty member on a course that would largely be taught by graduate students who had the time and energy to do these sorts of things. So we recruited professors to be the guarantors on courses which would be largely taught be people who were involved in defoliants, arms control and environmental issues.

So we got $1,000 from one of the university fellows who had some discretionary funds available and we printed up some pamphlets and showed up with card tables at registration in the fall of 1969 announcing the Stanford Workshops on Political and Social Issues. It had 10 faculty seminars and Stanford had never heard of the program.

The Tech: There seems to be a general movement towards more activism on campus but without any pressing issues like the Vietnam War it hasn’t amounted to much of anything. Do you have any impressions on activism today compared to when you were a student?

Jaffe: Students today are wonderful, certainly much better than students in the 1980’s, which were very dispiriting times for a faculty member at a place where you expect students to be imaginative and energetic. But I still think there is a tendency for students to look for solutions by petitioning the administration, by asking permission. I think it is a lot easier to ask for forgiveness than it is to ask for permission. I don’t mean for forgiveness for acting irresponsibly, I mean figuring out what resources are available, educate yourself on how to use them and bring them to play to solve your problem, looking for allies among the faculty, being responsible and taking things very seriously. The system will generally respond extremely positively to that. That model was there in the American student movement in the sixties and seventies, and it got lost, like a lot of things got lost.

The Tech: How did it get lost?

Jaffe: I think a lot of students concerns became institutionalized. There are many more people at a place like MIT whose job it is to be responsive to students needs then there were in the generation before. The responsibility for dealing with problems of that nature have been removed from the front line -- the students and the faculty -- and put in the hands of professionals.

The Tech: It is often said that student movements today aren’t like the sixties. This seems obvious -- there are different forms of communicating, different methods of organization, and different organizational structures within universities.

Jaffe: It’s also important to realize that there was an imperative in the society that students felt that the situation couldn’t be tolerated. There was a level of activism due to the presence of the war that has never been reproduced in any social issue since then. It’s not entirely a story of selfless motivation for the social good. One of the reason it happened was because Nixon started drafting college students. Suddenly you went from a situation where someone else was fighting your war to you fighting your war. It brought the situation home to a lot of middle class families in America. It is hard to finger issues of that magnitude in American society now.

The Tech: Switching gears to your professional life, I have read that you were appointed to a panel at Brookhaven National Laboratory to review whether or not an experiment there will destroy the Earth. What does this experiment hope to accomplish?

Jaffe: It is called RHIC, which stands for the relativistic heavy ion collider. The idea is to try to probe the structure of quarks and the systems they make up at very high densities and pressures. We know that protons and neutrons are made of quarks and that they interact with with each other by the exchange of quanta called gluons. We know the equations that govern these interactions, but they are very complicated and non-linear. We can solve them only in some simplifying limits. The challenge of this theory is that the laws are so simple and elegant, and we don’t know how to implement it.

It is pursuing that challenge that brings people to want to do these sort of experiments. The hope of the program at RHIC is to try to bring together two nuclei -- which gives us lots of quarks -- at very high energies and have them interact with each other head on. By colliding them head on they deposit lots of energy and, it is hoped, create a sort of plasma out of the quarks and gluons that will allow us to look for new forms of matter. We can also study the quarks and gluons under the conditions where we think we can understand their properties a little better.

The Tech: This article said that there were some concerns about strangelets and the possibility that a black hole might be created here on Earth. Can you talk about this?

Jaffe: Strangelets I think are legitimate, but basically unobtainable. I think they’re not a problem, but at least they are worth discussion. Black holes are simply an absurd issue, and were raised only by individuals who don’t understand the basic physics involved.

The bizarre behavior associated with strangelets were first suggested by theorists. The principle work was done by Ed Whitten at Princeton and by Ed Farhi and myself here at MIT. A strangelet is actually a little lump of a different form of hadronic matter. Ordinary nuclei, like iron -- iron is actually a good example because it is the most tightly bound nucleus -- are made up of protons and neutrons, and the quarks are packaged in the protons and neutrons.

If you were to squeeze iron tighter and tighter with some external pressure, you raise it to higher and higher densities, and the nucleon packages start to bump into each other or overlap more and more.

It is thought that the system makes a sort of transition to a state that is like a liquid of quarks or a gas of quarks. The system is driven to a different configuration by the external pressure. For example it is believed at the core or neutron stars where the pressure and density are highest the neutrons there are pressed into this “quark matter” phase. This gas or liquid of quarks is called quark matters. Quark matter made of neutrons and protons would only have the quarks that are in neutrons and protons - the up and down quarks. They are the lightest quarks, and they are what everything that is stable in nature is made out of. There is a complication in this story because there is a third kind of quark which is relatively low mass.

The third kind, the strange quark, has a low enough mass, so that when you put the system under high pressures the up and down quarks are pushed into higher and higher energy states by the Pauli exclusion principle because they have less volume. After a while the up and down quarks are forced into such a high energy level that it would pay to make one of them into a strange quark, because there are now strange quarks so the low energy states of the strange quark are available. We call this a symmetry energy effect.

If you could make quark matter it seems quite likely that the density would be high enough for the up and down quarks to spontaneously turn into strange quarks by the weak interaction.

Now comes the most clever piece of this physics. By changing up and down quarks into strange quarks we are lowering the energy and nature might actually lower the energy so much that this strange matter is lighter than the nuclear matter that it was made from in the first place. So it might be that in a scale of energies strange quark matter is lower energy than a nucleus like iron.

You can’t change iron into strange quark matter because there are no strange quarks in iron. We know that if you change one of the nucleons in iron into a nucleon containing a strange quark that the energy goes up not down. It is only when you have this gross rearrangement of the system from nucleons into a liquid of quarks and change all the quarks to strange quarks that the energy goes down.

Back in the 1980’s the idea that captivated the physics community was that the true ground state of matter was strange matter, not nuclei, but that we don’t see that because we are trapped in this meta-stable state of nuclei.

The Tech: So would this strange quark matter spread into other matter?

Jaffe: No, it is more complicated than that. The scenario that would cause a problem at RHIC is like one of those Rube Goldberg machines. It has got so many bells and whistles and improbabilities that by the end you feel it is impossible. So first strange matter may exist at the center of neutron stars, that is at least possible.

Then the question becomes when you release that external pressure, is that quark matter stable, or are nuclei stable. In order for the quark matter to be a danger it would have to be stable at zero external pressure. That is very unlikely.

The difference between the quark matter and nuclei is that eventually the positive charge of the nuclei causes it to become unstable at large masses. That doesn’t happen with strange quark matter, if it is stable, because the charge of the up plus the charge of the down and the charge of the strange is zero. As you keep adding more strange quark matter to it, instead of flying apart it just creates a larger and larger lump.

My work indicates that the smallest size a stranglet can be stable at is of the order of 50 -- about the size of iron. So this is another problem. Even if it is stable in bulk and stable at zero external pressure, it would have to be stable in small enough quantities so that you could make it at RHIC.

Even if it is stable in small quantities, it would be very difficult to make it at RHIC because the energy of the strangelet would have to be very low to be stable and the collisions at RHIC produce a lot of energy. Let’s suppose, once again, that this could happen. The last step in this Goldberg apparatus whereby strangelets would be a risk is that this lump of matter would have to be negatively charged.

If it were negative than when the strange matter approached another atom, it would go into orbit around the nucleus. However, this orbit would be so low because of its relatively high mass compared to an electron, that it would actually be orbiting inside the nucleus. Then it can convert that nucleus into strange matter in an exothermic reaction.

It continues this way until the strangelet is so heavy that it is no longer reasonable to view it as a little particle that wraps around the nucleus. It would become so massive that it would fall to the center of the earth and continue to expand until the reaction became catastrophic. The likelihood of this happening is so small that any reasonable person who learned about it would consider it to be impossible.

The Tech: But it is interesting physics.

Jaffe: It is an amusing sequence of steps and physicists like to explore lateral thinking. In our original paper in 1985 Fahri and I said, “We know that strange matter is not negatively charged and stable because if it were, we would not be here to write this paper.”

The Tech: So if it is so unlikely to occur, why was there a panel appointed to investigate it?

Jaffe: The sequence I outlined is the one that has lead people to question the safety or RHIC -- it’s what lead to the stories in the London Times and so on. As a consequence of the safety issues that were ranged, the director of Brookhaven is in a very difficult position. He is very eager to let people know that it is safe and that it is doing very interesting things for the world.

So when people raise safety questions he takes them very seriously. If someone raises an absurd safety question, he has two options. He can ignore it, or he can take it seriously and go at it like a typical science problem. His feeling was that if he ignored this, the accusation that he was not taking safety seriously would have been too damaging to the reputation of the laboratory. He feels he must take it seriously. However, by taking it seriously, he is also legitimizing it. People say, “This must be a problem because, after all, the director of Brookhaven appointed a panel to look at it.”

The Tech: What about a black hole forming?

Jaffe: That is absurd. The energy required to make a black hole out of two nuclei would be about 115 orders of magnitude larger than what will be available at RHIC.