"Great Gravity" is featured every edition of God & Nature Magazine, and tells the story of BNL physicist Bill Morse's journey through the world of muons and quarks, colliders and bubble chambers, with the light touch of a distinguished scientist still mightily in touch with his inner child, and with the heart of a committed Catholic and longtime-teacher of Sunday school. Read the first post in this series here.
The Great Ungainly Journey West
by Bill Morse
(Note: "Great Gravity!" is a serial column by Brookhaven National Laboratory physicist Bill Morse, about life, God, and physics, not necessarily in that order. Last season we heard about Bill's grad school days and his early work in particle physics. Read the last column here.)
In the 1970s, while I was finishing up my time at Purdue, Professors Steven Weinberg and Abdus Salam came up with a beautiful theory which unified the weak and the electromagnetic forces. However, in addition to the “charged current” that exists when a neutrino scatters from a neutron and becomes an electron and a proton, they predicted a “neutral current,” where a neutrino would scatter from a neutron, and would remain a neutrino without morphing into its partner, the electron. This was searched for at our neighboring experiment 1A at National Accelerator Laboratory (NAL, now Fermilab) and at the European Center for Particle Physics Research Lab in Geneva, Switzerland, called CERN.
The analyses alternately either saw the neutral current or ruled it out, hence the “alternating neutral current” description. Finally, both experiments had conclusive evidence that the neutral current exits: Weinberg and Salam's beautiful theory unifying the electromagnetic and weak forces was correct!
With the neutrino measurements in hand, the Weinberg-Salam theory predicted that the particle carrying the weak charged current would have a mass of about ninety times that of the proton, and the carrier of the neutral weak current would have a mass of about one hundred times the proton. More powerful accelerators were proposed in the U.S. and in Europe (CERN) to find these particles. The CERN proposal was funded, and they discovered the W and Z particles, which carry the weak force, in the same sense that the photon carries the electro-magnetic force, in the 1980s.
There was no beautiful theory of the strong force in the early 1970s. A popular theory was that when a proton stuck another proton, they heated up and "boiled off" pions. During the 1960s, many pion resonances had been discovered. These pion resonances could be explained if the proton and neutron were made of “quarks,” and the pion was made of a quark and an anti-quark. This quark model was developed by Professor Murray Gell-Mann and others. It was a beautiful model, but it didn’t explain what bound the quarks together into a proton, neutron, etc. We were going to higher energies to see how many more pions were boiled off, and if the quarks could be knocked out of the proton at these higher energies.
That's the theoretical background; now for the experimental background.
A bubble chamber is a marvelous device. It consists of a large tank of liquid just below the boiling point. Right after the beam particles passes through, the liquid boils wherever the particles traveled (since the energy they carry would heat the liquid further). Three cameras take pictures of the bubbles. Our bubble chamber was ready in 1972; however, NAL was taking longer to build the experiment than planned. The quote which I heard way too many times was "2B or not to be, that is the question." There were two grad students from Purdue on Experiment 2B, me and Roger Dixon. Roger despaired of NAL being done on time, so he joined an experiment Purdue was doing at Argonne National Lab. However, it turns out that experiment had technical difficulties, and he graduated only slightly before I did. He then got a job at NAL.
One day in January, 1972, to my amazement, I was called into the office of the Chairman of the Purdue Physics Department. I was very impressed by his large office, much larger than my small office that I shared with two other grad students. Earl Fowler had recently come to Purdue from Duke University. The undergraduates called him the "Duke of Earl," a popular song at that time. He said that he was doing an experiment at Stanford Linear Accelerator Center (SLAC) in Palo Alto, California, and he needed a grad student to go there for three months to help build his experiment. Since he had only recently arrived at Purdue, he didn't have a grad student yet. I told him I couldn't possibly go. His face fell a mile. I found out later that he had asked all the grad students, from the most senior to the most junior (me), and they had all said no. He asked why I couldn't go. I told him that it would cost a lot of money to drive to California, and then I would have to rent an apartment out there, and I just didn't have the money. He said, "Oh, but we'll pay your expenses." I said, "Wait a minute, you'll pay my expenses to go to California?" He said yes. I said I would have to ask Virgil first. Of course, he had already talked to Virgil, who said we were still waiting for NAL to be built, and it would be a good opportunity for me. So, in January I set off from Indiana to California in my 1964 Chevy Nova, which I had bought for $300 four years before.
I stopped in Illinois to get gas. It was cold and started to snow. After I filled up the tank, the car wouldn't start! The engine didn't turn over at all. I had seen my father short across the solenoid with a screwdriver in cases like this. I tried it and the engine started, and I was on my way again, but from then on I needed a hitch hiker or someone to pump the gas pedal while I shorted the solenoid.
When I got to Iowa it stopped snowing. I saw a pheasant out of the corner of my eye. Before I knew it, he crashed through the passenger's side front windshield! Luckily, I had just dropped off a hitchhiker who had been sitting there. I stopped in Sioux City, Iowa, and went to a service station. He said a windshield would cost $90. I asked if he would take a personal check. He said he didn't take out of state checks. I had a gasoline credit card, cash, and personal checks, but I might not have enough cash for the rest of the trip if I gave him $90. I asked him if he thought I could make it through the mountains to California with a piece of cardboard over the hole in the windshield. He said absolutely not! He said he would try to find a windshield at the local junkyard. Luckily he did and charged me only $10.
In Nebraska we were going up a long gradual hill when the engine just stopped. One of my hitchhikers climbed to the top of the hill, and said there was a service station at the bottom. We all got out and pushed the car to the top, and then jumped in and coasted down into the station. I told the mechanic the problem, and asked if he would take a personal check. He said he didn't accept out of state checks. It turned out that the car needed a new rotor, and he only charged me $10.
Going through Wyoming it got even colder and started snowing again when my car's heat failed! We stopped at a service station, but the mechanic couldn't find anything wrong. We continued on with the heat working, but then it soon stopped working again. In retrospect, this could have been because of the water pump which sometimes works and sometimes doesn’t work, depending on the conditions, which has happened to me several times since then, or it could have been that the coolant wasn’t adequately protected for that extreme cold, and it froze. I had two hitchhikers at that time. One of us would drive, one of us would talk to the driver so he wouldn't go to sleep, and the third was in my sleeping bag in the back trying to warm up. I didn't have enough money to stop at a motel, because I had assumed I would be using my personal checks, which no one was accepting. However, I saw a motel which was covered by my gasoline credit card! This motel chain was in Wyoming and further west. I stopped and checked in. It was nice and warm. I said I had two hitchhikers, and asked the clerk if they could sleep on the floor in my room. The clerk said no, there would be an additional charge. I asked my hitchhikers if they had enough money for the additional charge, and they both said no. I told the clerk that if they slept in my car, they might freeze to death, and that wouldn't look good in the local newspapers. He said he "wouldn't notice" if they came in. They were very glad to get warm.
We started out again in the morning. One hitchhiker continued on with me, the other decided to try to hitch a ride in a car with heat! The interstate highway was climbing up the Wasatch Mountain Range towards Utah. It was snowing hard. The engine died, so I pulled over to the side of the road. My hitchhiker said he would check the coolant. I knew this was exactly the wrong thing to do, but before I could stop him, he opened up the radiator cap, and the coolant blew all over the countryside. He said he had an uncle in Salt Lake City who would tow my car in. We stuck out our thumbs, and a kind soul picked us up, and dropped us off in Salt Lake City at his uncle's house, and he knocked on the door.
When his uncle opened the door, he said, "What are you doing AWOL again!" They were having a big argument: my hitch hiker said that he didn't like the army, but the uncle kept explained that didn't matter—he couldn't just go AWOL. I kept breaking in saying that it was snowing hard and we had to go get my car, but the uncle was just ignoring me. Finally, he heard me and said, "Who are you." I explained that his nephew had told me that he would tow my car in, which began a whole new argument! Finally he said he couldn't tow my car in because he was unemployed, and didn't have gas for his car. I told him I had a gasoline credit card and would fill up his car with gas. Everyone seemed happy with that deal, and we went back up the Wasatch Mountains to get my car.
When we got to my car, I put the transmission in neutral, attached a chain between my and his car, and he started towing me. Going up the pass was fine. However, going down the pass into Salt Lake City, somehow my car would go faster than his, so I would hit his bumper. Then I would put on my brakes, which would stretch the chain, and so on and so on. When we finally got to his house, the transmission was billowing smoke. I didn't know that you aren't supposed to tow a car with an automatic transmission unless you raise the drive wheels off the ground. Now both the engine and the transmission didn't work. I told him I would sign the title to the car over to him, if he would give me a ride to the airport. He seemed quite happy with that deal. I filled his car up with gas again, and was dropped off at the Salt Lake City airport.
I couldn’t take everything, so I left some things with him. That was the last time I used a pillow until I got married. Sara was surprised that I didn’t own a pillow, but I had just gotten used to not using one. I waited in the ticket line, and I asked for a ticket to San Francisco, and then asked if they would take a personal check. They said yes! I had an enjoyable three months at Stanford Linear Accelerator Center, and learned a lot. I bought a bicycle for $50 and enjoyed riding up into the Coastal Mountains behind Palo Alto, and took the train into San Francisco often. Earl Fowler bought the bicycle from me so that his new grad student could use it when he went to SLAC. I was glad to fly back to Purdue and see my friends again in April, 1972.
Read the next post in this series here.