51. Israel P. Edison, 309–310.
52. Berger H. The Mystery of a New Kind of Rays, 34.
53. Brown P. American Martyrs to Science Through the Roentgen Rays, 39–40.
54. Brown P. American Martyrs to Science Through the Roentgen Rays, 41.
55. Linton O. “Francis H. Williams and William H. Rollins.”
56. Brown P. American Martyrs to Science Through the Roentgen Rays, 17.
57. Brown P. American Martyrs to Science Through the Roentgen Rays, 17–18.
58. Brown P. American Martyrs to Science Through the Roentgen Rays, 29–30.
59. Einstein A. Relativity.
60. A nanometer is a unit of length equal to one billionth of a meter. Since a metric meter is about the length of British yard, a nanometer is approximately one billionth of a yard.
61. Ultraviolet radiation is also sometimes called black light, because it can’t be seen. (The purple glow from commercial black light bulbs used for special visual effects in nightclubs and other entertainment venues is due to the small amount of visible light in the violet range that contaminates the ultraviolet beam.)
62. An ion is an atom (or group of atoms) that has acquired an electric charge by gaining or losing some electrons.
CHAPTER 3: SEEK AND YOU SHALL FIND
1. Fluorescence and phosphorescence are two closely related luminescent phenomena that involve the storage and release of visible light by various chemicals. For the purposes of this book, we will use the term fluorescence to mean both.
2. Lindley D. Uncertainty, 33.
3. Uranium is a very heavy element (heavier than lead) that was discovered by M. H. Klaproth, a German scientist, in the 1790s. He gave it the name uranium in honor of planet Uranus, which had also just recently been discovered. Uranus was the ancient Greek god of the open sky.
4. If this coincidence had not been the case, it would likely have been many more years until radioactivity was discovered. But as fortune would have it, uranium sulfate happens to have both an unstable atomic nucleus (the uranium nucleus) and a photo-excitable electron shell. These atomic and chemical properties are unrelated to each other. The only fluorescent mineral in Becquerel’s collection that happened to have them both was uranium sulfate.
5. One becquerel (Bq) = one atomic disintegration per second.
6. Ore is any mined rock or earthen material that contains sufficient quantities of a mineral such that the mineral can feasibly be extracted for commercial purposes.
7. Zoellner T. Uranium, 130–179.
8. Badash L. Radioactivity in America, 11.
9. Clark C. Radium Girls, 43.
10. Badash L. Radioactivity in America, 11.
11. To be specific, this is a property of the radioisotope uranium-235. We will explore nuclear fission further in chapter 4.
12. This is generally true of the lighter elements. For the heavier elements, however, atoms tend to be most stable when there are somewhat more neutrons than protons.
13. Atoms can have unstable proton-neutron ratios for various reasons. Naturally occurring isotopes with unstable ratios are thought to be the remnants of a supernova that occurred at least six billion years ago. The supernova created our solar system and all of its isotopes in every conceivable proton-neutron ratio. Those isotopes with the most extreme ratios decayed away quickly. Those with ratios closer to one-to-one persisted, since they were more stable, and decayed much more slowly. Most long-lived natural radioisotopes (e.g., uranium) are supernova remnants. Alternatively, those natural radioisotopes with short lifetimes are usually produced from decay of a parent radioisotope with a longer lifetime (i.e., a radium parent decays to ultimately produce radon; chapter 5). Additionally, proton-neutron ratios can be artificially changed by bombardment with subatomic particles (see the splitting of the atom story in chapter 4, and the example of cobalt-60 production in chapter 6).
14. The emission of gamma rays from radioactive material was first discovered by Paul Villard, another Frenchman, in 1899 (Badash L. Radioactivity in America, 13).
15. Single photons cannot be identified as being either x- or gamma rays, but collectively they can be identified. This is because x-rays are emitted over a range of energies, while gamma-ray emissions are typically of a single energy (i.e., they are monoenergetic).
16. Willard Frank Libby (1908–1980) was awarded the Nobel Prize in Chemistry in 1960 for developing the technique of radiocarbon dating.
17. Marie Curie (née Maria Salomea Sklodowska) was ethnically Polish. She immigrated to France at the age of 24 to study at the Sorbonne (University of Paris).
18. Marie Curie alone was awarded another Nobel Prize in 1911 for the discovery of polonium and radium, because Pierre had died in 1906 and the Nobel Prize cannot be awarded posthumously.
19. The periodic table of elements is a tabular arrangement of all known elements, organized on the basis of their proton numbers, electronic configurations, and chemical properties. The table was invented by Russian scientist Dmitri Mendeleev (1834–1907) in about 1869, and remains the classic reference tool of chemists. A major utility of the table is that elements with similar chemical properties (i.e., those within the same chemical family) are listed within the same column of the table. Thus, knowing the column of an element allows chemists to deduce its chemistry (Kean S. The Disappearing Spoon).
20. To this day, some of Marie Curie’s scientific notebooks are too contaminated with radioactivity to be safely handled. They are currently in storage in lead-lined boxes in Paris.
21. Badash L. Radioactivity in America, 12.
22. The distance to the horizon at 1,000 feet above sea level is less than 100 miles.
23. Larson E. Thunderstruck, 116, 169, and 215.
24. Larson E. Thunderstruck, 312.
25. Larson E. Thunderstruck, 410.
26. The Heaviside layer is a stratum of ionized gas in Earth’s atmosphere found roughly 56–93 miles (90–150 kilometers) above the ground.
27. Larson E. Thunderstruck, 383.
CHAPTER 4: SPLITTING HAIRS
1. In reality there aren’t even plums in plum pudding. The recipe calls for raisins, which were commonly known as plums in pre-Victorian England, and plum pudding actually had the texture of a modern-day, moist and dense muffin, rather than the creamy consistency of American pudding.
2. Davis E. A., and I. J. Falconer. J.J. Thomson and the Discovery of the Electron.
3. Another apt analogy for the size of the nucleus within an atom is “a fly in a cathedral.”
4. The historical accounts of the discoveries of scientists working at the Cavendish laboratory that appear in this chapter are largely drawn from the excellent book, The Fly in the Cathedral by Brian Cathcart. Biographical accounts of the life of Ernest Rutherford come from the authoritative scholarly biography, Rutherford: Scientist Supreme by John Campbell.
5. Kean S. The Disappearing Spoon, 301.
6. Reeves R. A Force of Nature, 31.
7. Cathcart B. The Fly in the Cathedral, 21.
8. Frederick Soddy would win the Nobel Prize in Chemistry in 1921 for work he performed at McGill on the radioactive decay and isotope theory.
9. Rutherford E. Radio-Activity.
10. The first use of the term in connection with radioactivity is actually attributed to Frederick Soddy. When Soddy first realized that radioactive decay was converting one element into another, he is said to have exclaimed, “Rutherford this is transmutation!” Rutherford retorted: “For Mike’s sake, Soddy, don’t call it transmutation. They’ll have our heads off as alchemists.” Later, Rutherford was proud to use the term in connection with his work.
11. Campbell J. Rutherford, 478–481.
12. As of 2014, 29 Cavendish researchers have won Nobel Prizes.
13. Crowther J. G. The Cavendish Laboratory 1874–1974.
14. The actual source of helium for balloons and other purposes is the pockets of gas that form in porous rock when radioactive minerals deep within
Earth decay, releasing alpha particles. The alpha particles take on electrons and become helium gas. The gas is trapped and cannot escape to Earth’s surface, so it accumulates in porous rock. Rutherford once attempted to date the Earth’s age based on the helium gas content of its rocks and the known half-lives of the radioactive minerals within them. His data suggested that Earth was at least 40 million years old. His methods were inaccurate, however, and scientists now know that our planet is at least 4 billion years old.
15. Rutherford used gold because it was inert (i.e., it didn’t chemically react with other things) and because it was easily malleable into thin foils, making it convenient for experimentation. Other elements didn’t have these practical advantages, but they would have worked as well.
16. Lindley D. Uncertainty, 46–47.
17. Italian scientist Amedeo Avogadro (1776–1856) proposed in 1811 that the volume of a gas is proportional to the included number of atoms regardless of the type of gas. (Actually, he said that all gases at standard temperature and pressure will have equal numbers of molecules, not atoms, but since the chemists also knew the number of atoms per molecule, they could adjust their calculations for gas molecules that contained more than one atom.)
18. Since the very small electrons contribute negligible amounts to atomic mass, their masses can be disregarded in the calculation.
19. Neutrons also served to dilute the positive electrical charge of the nucleus, because a nucleus composed only of self-repulsing protons would blow itself apart.
20. Cathcart B. The Fly in the Cathedral, 208.
21. The nucleus of a hydrogen atom consists of a single proton.
22. An electron volt (eV) is a unit of energy equal to the work done when an electron is accelerated through a potential difference of one volt. Historically, the eV was developed as a unit because of its usefulness in particle accelerator sciences. But it is not part of the International System of Units (SI), which employs the unit of joules rather than eV.
23. Cathcart B. The Fly in the Cathedral, 141.
24. Badash L. Radioactivity in America.
25. Cathcart B. The Fly in the Cathedral, 185.
26. Radon has been a very important player in the story of radiation’s health effects. We will learn much more about radon in chapter 12.
27. The now defunct Kelly Hospital was at that time the country’s leading center for radiation therapy of gynecologic cancers. Named after its founder and head, the gynecologic surgeon Howard Atwood Kelly, the Kelly hospital staff probably felt that by giving the tubes to the Cavendish scientists they were indirectly returning a favor to Ernest Rutherford. It was Rutherford who had originally given Kelly, in about 1912, an apparatus to collect radon gas from radium (Aronowitz et al. “Howard Kelly establishes gynecologic brachytherapy”).
28. Ironically, the word atom comes from the Greek ἂτoµoς; (atomos), meaning uncuttable or indivisible, as in something that can be divided no further. So the ancient Greeks would have considered a split atom the ultimate oxymoron.
29. This is just the opposite of what a Crookes tube does when it accelerates negatively charged electrons toward a positively charged anode (see chapter 2).
30. Poole M., et al. “Cockcroft’s subatomic legacy.”
31. Cathcart B. The Fly in the Cathedral, 66–84.
32. Cathcart B. The Fly in the Cathedral, 165.
33. Cockcroft and Walton won the 1951 Nobel Prize in physics for “Transmutation of atomic nuclei by artificially accelerated atomic particles.” Translated into plain English: They split the atom. Strictly speaking, Rutherford had already done this in 1917 when he produced transmutations by alpha-particle bombardment of nitrogen, but the expression “splitting the atom” did not come into widespread use until later, and then more typically in connection with Cockcroft and Walton’s proton accelerator cleavage of lithium than with Rutherford’s alpha-particle transmutations of nitrogen.
34. Cathcart B. The Fly in the Cathedral, 158.
35. Cathcart B. The Fly in the Cathedral, 64, 106.
36. Cathcart B. The Fly in the Cathedral, 159.
37. To be accurate, we are talking about mass (kilograms), not weight (pounds). Weight is affected by gravity, while mass is not. For example, astronauts would weigh less (in pounds) on the moon than on Earth due to lower gravity, but their mass (in kilograms) would be unchanged. The difference between mass and weight is an important scientific distinction, but the terms are sometimes used interchangeably in common speech. For our purposes, we will use the noun “mass” and its unit kilograms, with the verb, “to weigh” (because the verb “to mass” does not exist).
38. The international standard unit of energy is the joule (J). One J is equal to: (kg × m2)/s2.
39. Isaacson W. Einstein, 272.
40. Cathcart B. The Fly in the Cathedral, 250.
41. Kelly C. C. The Manhattan Project.
42. Fermi had also been supremely confident when he announced his discovery of transuranic elements. Nevertheless, after he had already been awarded the 1938 Nobel Prize in Physics for the discovery, he was proven wrong. His transuranic elements were actually just fission products. The true transuranic elements were discovered some time later by Edwin Mattison McMillan (1907–1991). Reluctant to admit its mistake, the Nobel committee awarded McMillan the 1951 Nobel in Chemistry, and allowed Fermi to retain his Nobel in Physics (Kean S. The Disappearing Spoon, 141–143).
43. The Chicago Pile is now buried in eternal rest in Red Gate Woods, a forest preserve within the Palos Division of the Forest Preserve District, Cook County, Illinois.
44. For a short and cogent explanation of how nuclear fusion releases energy, see Close F. Particle Physics: A Very Short Introduction, 107–111.
45. Cosmic radiation actually includes all radiation originating anywhere in space, not just from solar flares.
46. Brooks M. 13 Things That Don’t Make Sense, chapter 4.
47. A hydrogen gas explosion is not the same as a hydrogen bomb. Hydrogen gas (H2) is highly reactive with oxygen gas (O2) and can cause a chemical explosion that results in the production of water (H2O), but this is not the same as a hydrogen nuclear fusion reaction. Hydrogen gas chemical explosions did occur at the Fukushima nuclear power plant accident in 2011, but it is not possible for a nuclear hydrogen fusion explosion to occur at a nuclear fission power plant.
CHAPTER 5: PAINTED INTO A CORNER
1. Schneeberg (Germany) and St. Joachimsthal (Czech Republic) are neighboring mining communities in the Ore Mountains—a mountain range that straddles the present-day border between Germany and the Czech Republic. The Ore region has a long history of mining various minerals, and the term “ore”—a naturally occurring solid material from which minerals can commercially be extracted—received its name from this place.
2. Schuttmann W. “Schneeberg lung disease and uranium mining.”
3. Isaac Newton worked extensively with mercury (then called quicksilver). Samples of his hair were analyzed in 1979 and found to contain mercury at toxic levels. But it is not clear whether the mental illness that he suffered later in his life can be explained by the mercury (Gleick J. Isaac Newton, 99).
4. Clark C. Radium Girls, 20.
5. Rodricks J. V. Calculated Risks, 136–161.
6. It was often the practice of coal miners to bring caged canaries into the mines to detect the presence of methane gas, which is lethal. Canaries are extremely sensitive to methane. If a miner’s canary died, it suggested the presence of the gas, and the miners evacuated before they succumbed to the methane fumes.
7. As we have already seen, the early researchers of the ionizing radiations (e.g., x-rays, gamma rays, beta particles, alpha particles, neutrons, etc.) often suffered skin irritations as a consequence of their research, and cancers sometimes later developed in the same body areas that had been irritated. Roentgen was aware of this, and he protected himself with lead shielding while experimenting with x-rays. The less cautious scientists and engineers,
like the Curies and Edison, suffered significant health consequences due to their relatively high exposures. In contrast, Marconi and other pioneers of the nonionizing radiations (e.g., radio waves) suffered no apparent health effects even from massive exposures, suggesting that the ionizing radiations were potentially dangerous while the nonionizing radiations were not.
8. To be perfectly accurate, a rarer radioisotope of radon (radon-220) was first discovered in 1899, by Ernest Rutherford (Marshall J. L., and V. R. Marshall. “Ernest Rutherford”).
9. An older term “daughter” is sometimes used instead of “progeny.” (Although it may be politically incorrect, no decay products are ever called “sons.”)
10. Lorenz E. “Radioactivity and lung cancer.”
11. Waterbury Observer, “After glow.”
12. The first person to actually invent a radium-based fluorescent paint was William J. Hammer in 1902, but he did not attempt to patent it because he thought radium was too scarce and costly to have any practical use in paint. But George F. Kunz, an executive at the exclusive jewelry firm, Tiffany & Company, stole Hammer’s idea, patented the paint in 1903, and used it to adorn several jewelry items that were sold to wealthy buyers in their Manhattan store. Radium paint would not come into widespread use until rising medical demands for radium greatly increased commercial radium production to the point that prices started to come down (see chapter 6).
13. Clark C. Radium Girls, 15.
14. Clark C. Radium Girls, 108–109.
15. Hacker B. C. The Dragon’s Tail, 22.
16. The term irradiate is a verb meaning the act of exposing something to radiation.
17. Recall that carbon-14 (six protons) decays into nitrogen-14 (seven protons); see chapter 2.
18. NCRP Report. Some Aspects of Strontium Radiobiology.
19. The Waterbury Clock Company would ultimately become Timex.
20. Clark C. Radium Girls, 161.
21. Quinn S. Marie Curie, 411.
22. Quinn S. Marie Curie, 410.
23. Clark C. Radium Girls, 172–176.
24. Clark C. Radium Girls, 172.
25. Physicians were offered a discounted rate of $25.00 per case.
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