When Science Goes Wrong (39 page)
Schwartz confessed to me that (like so many other people who have taken an interest in the case) he had not actually read the Tudor study but was dependent on information and extracts provided by others, especially by Ambrose and Yairi.
Most commentators have expressed criticisms of the Tudor study similar to those put forward by Schwartz. Ambrose and Yairi, for example, wrote that ‘It is unquestionable that the study was ethically wrong.’ But, one person has mounted a vigorous defence of Wendell Johnson – his son. Nicholas Johnson, a law professor at the University of Iowa, wrote an article in which he maintained that historical research should be judged only by the ethical standards of its own time. He then came up with a laundry list of equally or even more questionable studies from that general period, including the infamous Tuskegee syphilis study in which poor black men were denied access to treatment for their syphilis for many years. According to the younger Johnson, his father and his father’s student did nothing that was outside the bounds of normal research practice at the time.
Much of what Nicholas Johnson says is perfectly true: researchers did often take advantage of institutionalised persons for research in those days, sometimes inflicting worse harm on them than Mary Tudor probably did to her subjects. But the interest in revisiting ethical questions about a historical study such as Johnson’s is not – except perhaps for Johnson’s son and a bunch of lawyers – to pass retroactive moral judgment on the deceased persons who conceived it and carried it out. Rather, it is to highlight the reasons why it is necessary to have written regulations governing the use of human subjects in research today, as well as IRBs to enforce them.
Nicholas Johnson has also attempted to defend his father by pointing out that Tudor herself – who has largely escaped personal criticism – should share whatever blame is assigned for the study. Certainly graduate students need to accept responsibility for their actions, but in this particular case it is clear that the project was entirely Wendell Johnson’s idea. When I read Tudor’s thesis, I was struck by her near-total lack of interest in the issues that her project addressed; even though her Introduction briefly mentioned Johnson’s diagnosogenic theory as the inspiration for the study, her Discussion – also very brief – included no assessment of what her findings meant for the theory. In general, Tudor’s thesis reads like the work of an industrious low-level operative who followed her advisor’s instructions to the letter, and who considered her job complete when she had done so.
‘Whether there was true harm or not, [Johnson and Tudor’s] subjects were intruded on in a way that they shouldn’t have been,’ commented Schwartz by way of wrapping up the ethical issues. ‘They should have given this more thought, even given the mores of the time. Most importantly, it’s a useful thing today to teach both senior researchers like myself, and students, that you really have to think about these things. It’s very important, if anything, to err on the side of being cautious and more protective of human subjects and to be really good at perspective-taking: “What would this be like if this were my child, my relative, me, in the situation of being a subject; would this be OK?” And this is really at the heart of what an IRB tries to do.’
NUCLEAR CHEMISTRY: The Magic Island
IN AUGUST 1999, NUCLEAR chemists at the Lawrence Berkeley National Laboratory announced the creation of three atoms of a new ‘superheavy’ element, element 118. Two years later they had to retract their claim, and a firefight broke out that cost a star scientist his career and sullied the reputations of several others.
The University of California’s Berkeley campus had been a world leader in the discovery of new elements since 1940, when Edwin McMillan discovered element 93, neptunium. The university’s most famous element hunter was Glenn Seaborg, who discovered plutonium (element 94) in 1941 and followed it up with nine more elements, culminating in 1974 with the one that was named, in his honour, seaborgium (element 106). McMillan and Seaborg shared the 1951 Nobel Prize for Chemistry, but many other Berkeley scientists also played important roles in this work. These included Stanley Thompson, who helped discover most of the new elements up to element 101, and Albert Ghiorso, who shared credit for many of the elements discovered from the mid-1940s onward.
The use of the term ‘discover’ in this context is slightly odd. Darleane Hoffman (also a Berkeley Lab scientist since 1984) and others did discover minute amounts of plutonium and neptunium in natural uranium ores, but none of the other ‘transuranium’ elements exist in the natural world, unless perhaps in some distant supernova. Thus the process of discovery means
creating
them, not finding them as the term implies. In part, scientists use the term
discover
simply as a continuation of a tradition that started with the actual discovery of the lighter elements in nature. In addition, however, they probably use the term because they think of the transuranium elements as already existing in a Platonic universe to which their powerful instruments give them entry. They think this way because the properties of each element – even those that don’t exist – were fixed at the beginning of time, when the particles that make up atomic nuclei (the positively charged protons and uncharged neutrons) were endowed with their immutable characteristics.
To some extent, then, nuclear chemists can predict the properties of atomic nuclei that haven’t yet been discovered or created. The most basic theoretical formulation is this: the protons and neutrons are held tightly together by the ‘nuclear force’, which only acts over minute distances. Countering this attraction is the electrostatic repulsion between the protons’ positive charges, which tends to push them apart; this force acts over a much greater distance than the nuclear force. As one progresses to heavier and heavier nuclei, they become less and less stable, because the protons and neutrons cannot crowd closely enough together for the nuclear force to act at full strength between all the particles. Thus the electrostatic repulsion comes to dominate, causing the nucleus to break apart.
If this were the whole story, there would have to be an end to the periodic table of the elements, and that end would lie somewhere in the neighbourhood of element 106, the last element that Seaborg discovered. During the 1980s and 1990s, however, elements 107 to 112 were created – roughly in the sequence of their atomic numbers. Most of these discoveries were made by a group at the Institute for Heavy Ion Research (GSI) in Darmstadt, Germany. A Russian group, the Joint Institute for Nuclear Research in Dubna, near Moscow, was also a player.
The existence of these heavier elements had in fact been predicted by theorists who went beyond the simple model of the atomic nucleus just described. One of these theorists was Seaborg’s Polish-born colleague Wladyslaw Swiatecki, who joined the Berkeley group in 1957. Swiatecki and others believed that, within the nucleus, protons occupy a series of discrete energy levels that can be thought of as concentric shells. A nucleus whose outermost proton shell was completely filled would gain an extra measure of stability beyond that predicted by classical theory. Similarly, neutrons were thought to reside in their own shells and to confer extra stability on the nucleus when their outermost shell was filled. These nuclear shells are analogous to the better-known electron shells outside of the nucleus, which are filled in the inert gas elements helium, neon, and so on.
The numbers of protons and neutrons that conferred stability were said to be ‘magic’, and a nucleus that contained magic numbers of both protons and neutrons were ‘doubly magic’. These might exist in sizes far beyond the limits set by classical theory. In other words, even element 112 might not be the end of the road.
Not everyone agreed on exactly what these magic numbers of protons and neutrons were, or even whether they were meaningful concepts at all. Still, this was the conceptual framework that guided research in the 1990s. And what it meant was that simply going for the next-heaviest undiscovered element on the list might not be the best approach: some elements well beyond the presently achieved limits might actually be more stable and easier to create.
Also, this approach meant that both the number of protons (which defines which element we are talking about) and the number of neutrons (which defines which isotope of that element we are talking about) needed to be considered when thinking about creating superheavy elements. To illustrate this, Seaborg, Swiatecki and others used a chart that plotted the proton number (on the vertical axis) and the neutron number (on the horizontal axis) of all known atomic nuclei. On this chart, the already-known nuclei formed a long, narrow cluster running from the bottom left (a hydrogen nucleus) toward the top right (the currently heaviest element). The cluster resembled the image of the Outer Hebrides as seen on a map. Outside this cluster lay a ‘sea of instability’ in which nuclei could not exist, or not for long enough to be detected. Yet across this sea in a direction farther upward and to the right (corresponding, say, to the location of Shetland), might lie ‘islands of stability’ or ‘magic islands’ – the homes of yet-undiscovered superheavy nuclei with sets of protons and neutrons close to doubly magic numbers. The rumoured existence of these islands offered as powerful a lure to nuclear chemists as the fabled Spice Islands did to the explorers of old.
There seem to have been some differences of opinion within the Berkeley Lab concerning these ideas. Darleane Hoffman and Albert Ghiorso clearly believed in the idea of islands of stability or magic islands, because in a 2000 book they frequently used these phrases when describing their laboratory’s goals. I got a different story from Walter Loveland, a somewhat younger nuclear chemist from Oregon State University who joined the Berkeley Lab for the 1998-1999 year, and who played an important role in the ill-fated search for element 118. ‘I would disabuse you of this idea of the “island of stability”,’ he said in a 2006 interview. ‘Those predictions were made in the 1960s when it was thought that there would be a group of elements with half-lives that were long even relative to the age of the universe, and that they’d form this island. We don’t believe in that anymore – that’s not right. What we know is that there may be nuclei whose half-lives are longer than their neighbours’, but they seem to be connected to the mainland of lighter elements by a peninsula. They are not islands in a sea of instability.’
By 1998, when the effort to detect element 118 began, Berkeley’s glory days of element hunting were long over. Stanley Thompson had died in 1976*. Seaborg was 86, and in August of 1998 he suffered a devastating stroke that led to his death six months later. Ghiorso was 83; Swiatecki and Hoffman, the youngsters, were 72 and 71. Room 307 of Berkeley’s Gilman Hall, where Seaborg identified plutonium, had been a US National Historic Landmark for 32 years. And though much other good work had been done at the Berkeley Lab, not a single new element had been discovered there in more than two decades.
The Berkeley Lab did have the tools to produce superheavy elements, however. One essential tool was the 88-inch Cyclotron – the giant descendant of the hand-held ‘proton merry-go-round’ invented by Ernest Lawrence in the 1920s. The Cyclotron accelerates nuclei of a chosen isotope (let’s say
48
Ca, which are calcium nuclei with 20 protons and 28 neutrons, yielding a total mass number of 48) to speeds that can exceed 1,000 kilometres per second, giving them tremendous kinetic energy.
A steady beam of these energetic nuclei emerges from the Cyclotron and enters another piece of equipment, the gas-filled separator. This instrument was built by a Berkeley group led by Ken Gregorich, who belongs to a younger generation; he was one of Seaborg’s last graduate students. Within the separator, the beam passes through a thin foil made from another isotope, such as 244Pu (plutonium with 94 protons and 150 neutrons). The hope is that a very occasional beam nucleus will strike a target nucleus just right. If so, the kinetic energy of the beam nucleus overcomes the electrostatic repulsion between the two negatively charged nuclei (known as the Coulomb barrier) and the two nuclei fuse, yielding a compound nucleus. In this example it has 114 protons (making it the as-yet-unnamed superheavy element 114) plus 178 neutrons.
Because of the kinetic energy of the incoming
48
Ca missile, the compound nucleus is put in an excited state, like a drop of water brought nearly to a boil. Most of this excitation energy is carried off almost instantly by the ‘evaporation’ of a few neutrons. The remaining, slightly lighter isotope of element 114 flies onward through the instrument, and a series of magnets deflect it from the main beam and deposit it onto a silicon detector. This nucleus is itself unstable: it breaks down into lighter nuclei over some period of time that might range from microseconds to minutes. The detector identifies the time, location and energy of the particles produced in these sequential breakdown events, and from this data the superheavy nucleus that gave rise to them can be identified.
Voila
, a new element – element 114 in the case of this hypothetical example – albeit just a single atom and a very short-lived one at that.
