Radium is a chemical element with symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table known as the alkaline earth metals. Pure radium is silvery-white, but it reacts with nitrogen on exposure to air, forming a black surface layer of radium nitride. All isotopes of radium are radioactive, with the most stable isotope being radium-226, which has a half-life of 1600 years and decays into radon gas; when radium decays, ionizing radiation is a product, which can excite fluorescent chemicals and cause radioluminescence. Radium, in the form of radium chloride, was discovered by Marie and Pierre Curie in 1898, they extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1911. In nature, radium is found in uranium and thorium ores in trace amounts as small as a seventh of a gram per ton of uraninite.
Radium is not necessary for living organisms, adverse health effects are when it is incorporated into biochemical processes because of its radioactivity and chemical reactivity. Other than its use in nuclear medicine, radium has no commercial applications. Today, these former applications are no longer in vogue because radium's toxicity has since become known, less dangerous isotopes are used instead in radioluminescent devices. Radium is the only radioactive member of its group, its physical and chemical properties most resemble its lighter congener barium. Pure radium is a volatile silvery-white metal, although its lighter congeners calcium and barium have a slight yellow tint; this tint vanishes on exposure to air, yielding a black layer of radium nitride. Its melting point is either 700 °C or 960 °C and its boiling point is 1,737 °C. Both of these values are lower than those of barium, confirming periodic trends down the group 2 elements. Like barium and the alkali metals, radium crystallizes in the body-centered cubic structure at standard temperature and pressure: the radium–radium bond distance is 514.8 picometers.
Radium has a density of 5.5 g/cm3, higher than that of barium, again confirming periodic trends. Radium has 33 known isotopes, with mass numbers from 202 to 234: all of them are radioactive. Four of these – 223Ra, 224Ra, 226Ra, 228Ra – occur in the decay chains of primordial thorium-232, uranium-235, uranium-238; these isotopes still have half-lives too short to be primordial radionuclides and only exist in nature from these decay chains. Together with the artificial 225Ra, these are the five most stable isotopes of radium. All other known radium isotopes have half-lives under two hours, the majority have half-lives under a minute. At least 12 nuclear isomers have been reported. In the early history of the study of radioactivity, the different natural isotopes of radium were given different names. In this scheme, 223Ra was named actinium X, 224Ra thorium X, 226Ra radium, 228Ra mesothorium 1; when it was realized that all of these are isotopes of the same element, many of these names fell out of use, "radium" came to refer to all isotopes, not just 226Ra.
Some of radium-226's decay products received historical names including "radium", ranging from radium A to radium G, with the letter indicating how far they were down the chain from their parent 226Ra.226Ra is the most stable isotope of radium and is the last isotope in the decay chain of uranium-238 with a half-life of over a millennium: it makes up all of natural radium. Its immediate decay product is the dense radioactive noble gas radon, responsible for much of the danger of environmental radium, it is 2.7 million times more radioactive than the same molar amount of natural uranium, due to its proportionally shorter half-life. A sample of radium metal maintains itself at a higher temperature than its surroundings because of the radiation it emits – alpha particles, beta particles, gamma rays. More natural radium emits alpha particles, but other steps in its decay chain emit alpha or beta particles, all particle emissions are accompanied by gamma rays. In 2013 it was discovered; this was the first discovery of an asymmetric nucleus.
Radium, like barium, is a reactive metal and always exhibits its group oxidation state of +2. It forms the colorless Ra2+ cation in aqueous solution, basic and does not form complexes readily. Most radium compounds are therefore simple ionic compounds, though participation from the 6s and 6p electrons is expected due to relativistic effects and would enhance the covalent character of radium compounds such as RaF2 and RaAt2. For this reason, the standard electrode potential for the half-reaction Ra2+ + 2e− →
National Institute of Standards and Technology
The National Institute of Standards and Technology is a physical sciences laboratory, a non-regulatory agency of the United States Department of Commerce. Its mission is to promote industrial competitiveness. NIST's activities are organized into laboratory programs that include nanoscale science and technology, information technology, neutron research, material measurement, physical measurement; the American AI initiative has called NIST to lead the development of appropriate technical standards for reliable, trustworthy, secure and interoperable AI systems. The Articles of Confederation, ratified by the colonies in 1781, contained the clause, "The United States in Congress assembled shall have the sole and exclusive right and power of regulating the alloy and value of coin struck by their own authority, or by that of the respective states—fixing the standards of weights and measures throughout the United States". Article 1, section 8, of the Constitution of the United States, transferred this power to Congress.
To coin money, regulate the value thereof, of foreign coin, fix the standard of weights and measures". In January 1790, President George Washington, in his first annual message to Congress stated that, "Uniformity in the currency and measures of the United States is an object of great importance, will, I am persuaded, be duly attended to", ordered Secretary of State Thomas Jefferson to prepare a plan for Establishing Uniformity in the Coinage and Measures of the United States, afterwards referred to as the Jefferson report. On October 25, 1791, Washington appealed a third time to Congress, "A uniformity of the weights and measures of the country is among the important objects submitted to you by the Constitution and if it can be derived from a standard at once invariable and universal, must be no less honorable to the public council than conducive to the public convenience", but it was not until 1838, that a uniform set of standards was worked out. In 1821, John Quincy Adams had declared "Weights and measures may be ranked among the necessities of life to every individual of human society".
From 1830 until 1901, the role of overseeing weights and measures was carried out by the Office of Standard Weights and Measures, part of the United States Department of the Treasury. In 1901, in response to a bill proposed by Congressman James H. Southard, the National Bureau of Standards was founded with the mandate to provide standard weights and measures, to serve as the national physical laboratory for the United States. President Theodore Roosevelt appointed Samuel W. Stratton as the first director; the budget for the first year of operation was $40,000. The Bureau took custody of the copies of the kilogram and meter bars that were the standards for US measures, set up a program to provide metrology services for United States scientific and commercial users. A laboratory site was constructed in Washington, DC, instruments were acquired from the national physical laboratories of Europe. In addition to weights and measures, the Bureau developed instruments for electrical units and for measurement of light.
In 1905 a meeting was called that would be the first "National Conference on Weights and Measures". Conceived as purely a metrology agency, the Bureau of Standards was directed by Herbert Hoover to set up divisions to develop commercial standards for materials and products.page 133 Some of these standards were for products intended for government use, but product standards affected private-sector consumption. Quality standards were developed for products including some types of clothing, automobile brake systems and headlamps and electrical safety. During World War I, the Bureau worked on multiple problems related to war production operating its own facility to produce optical glass when European supplies were cut off. Between the wars, Harry Diamond of the Bureau developed a blind approach radio aircraft landing system. During World War II, military research and development was carried out, including development of radio propagation forecast methods, the proximity fuze and the standardized airframe used for Project Pigeon, shortly afterwards the autonomously radar-guided Bat anti-ship guided bomb and the Kingfisher family of torpedo-carrying missiles.
In 1948, financed by the United States Air Force, the Bureau began design and construction of SEAC, the Standards Eastern Automatic Computer. The computer went into operation in May 1950 using a combination of vacuum tubes and solid-state diode logic. About the same time the Standards Western Automatic Computer, was built at the Los Angeles office of the NBS by Harry Huskey and used for research there. A mobile version, DYSEAC, was built for the Signal Corps in 1954. Due to a changing mission, the "National Bureau of Standards" became the "National Institute of Standards and Technology" in 1988. Following September 11, 2001, NIST conducted the official investigation into the collapse of the World Trade Center buildings. NIST, known between 1901 and 1988 as the National Bureau of Standards, is a measurement standards laboratory known as a National Metrological Institute, a non-regulatory agency of the United States Department of Commerce; the institute's official mission is to: Promote U. S. innovation and industrial competitiveness by advancing measurement science and technology in ways that enhance economic security and improve our quality of life.
NIST had an operating budget for fiscal year 2007 of about $843.3 million. NIST's 2009 budget was $992 million
The roentgen or röntgen is a legacy unit of measurement for the exposure of X-rays and gamma rays. It is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air. In 1928 it was the first international measurement quantity for ionising radiation to be defined for radiation protection, was an replicated method of measuring air ionization directly by using an ion chamber, it is named after the German physicist Wilhelm Röntgen. Although easy to measure, the roentgen had the disadvantage that it was only a measure of air ionisation and not a direct measure of radiation absorption in other materials; as the science of radiation dosimetry developed, it was realised that the ionising effect, hence tissue damage, was linked to energy absorbed, not just radiation exposure. New radiometric units for radiation protection were defined which took this into account. In 1953 the International Commission on Radiation Units and Measurements recommended the rad, equal to 100 erg/g, as the unit of measure of the new radiation quantity absorbed dose.
The rad was expressed in coherent cgs units. In 1975 the unit gray was named as the SI unit of absorbed dose; the gray was equal to the cgs unit. Additonally, a new quantity Kerma was defined for air ionisation, is the modern metrological, but not radiation protection, successor to the roengten, from this the absorbed dose can be calculated using known coefficients for specific target materials. In radiation protection the absorbed dose is the energy absorption, an indication of acute tissue effects occurring at high dose rates, from low levels of absorbed dose the equivalent dose, representing the stochastic health risk, can be calculated; the roengten has been redefined over the years. It was last defined by the US National Institute of Standards and Technology in 1998 as 2.58×10−4 C/kg, with a recommendation that the definition be given in every document where the roentgen is used. One roentgen deposits 0.00877 grays of absorbed 0.0096 Gy in soft tissue. One roentgen of X-rays may deposit anywhere from 0.01 to 0.04 Gy in bone depending on the beam energy.
This tissue-dependent conversion from kerma to absorbed dose is called the F-factor in radiotherapy contexts. The conversion depends on the ionizing energy of a reference medium, ambiguous in the latest NIST definition; the roentgen has its roots in the Villard unit defined in 1908 by the American Roentgen Ray Society as "the quantity of radiation which liberates by ionisation one esu of electricity per cm3 of air under normal conditions of temperature and pressure." Using 1 esu ≈ 3.33564×10−10 C and the air density of ~1.293 kg/m³ at 0 °C and 101 kPa, this converts to 2.58 × 10−4 C/kg, the modern value given by NIST. 1 esu/cm3 × 3.33564 × 10−10 C/esu × 1,000,000 cm3/m3 ÷ 1.293 kg/m3 = 2.58 × 10−4 C/kg This definition was used under different names for the next 20 years. In the meantime, the French Roentgen was given a different definition which amounted to 0.444 German R. In 1928, the International Congress of Radiology defined the roentgen as "the quantity of X-radiation which, when the secondary electrons are utilised and the wall effect of the chamber is avoided, produce in 1 cc of atmospheric air at 0 °C and 76 cm of mercury pressure such a degree of conductivity that 1 esu of charge is measured at saturation current."
The stated 1 cc of air would have a mass of 1.293 mg at the conditions given, so in 1937 the ICR rewrote this definition in terms of this mass of air instead of volume and pressure. The 1937 definition was extended to gamma rays, but capped at 3 MeV in 1950; the USSR all-union committee of standards had meanwhile adopted a different definition of the roentgen in 1934. GOST standard 7623 defined it as "the physical dose of X-rays which produces charges each of one electrostatic unit in magnitude per cm3 of irradiated volume in air at 0 °C and normal atmospheric pressure when ionization is complete." The distinction of physical dose from dose caused confusion, some of which may have led Cantrill and Parker report that the roentgen had become shorthand for 83 ergs per gram of tissue. They named this derivative quantity the roentgen equivalent physical to distinguish it from the ICR roentgen; the introduction of the roentgen measurement unit, which relied upon measuring the ionisation of air, replaced earlier less accurate practices that relied on timed exposure, film exposure, or fluorescence.
This led the way to setting exposure limits,and the National Council on Radiation Protection and Measurements of the United States established the first formal dose limit in 1931 as 0.1 roentgen per day. The International X-ray and Radium Protection Committee, now known as the International Commission on Radiological Protection soon followed with a limit of 0.2 roentgen per day in 1934. In 1950, the ICRP reduced their recommended limit to 0.3 roentgen per week for whole-body exposure. The International Commission on Radiation Units and Measurements took over the definition of the roentgen in 1950, defining it as "the quantity of X or γ-radiation such that the associated corpuscular emission per 0.001293 gram of air produces, in air, ions carrying 1 electrostatic unit of quantity of electricity of either sign." The 3 MeV cap was no longer part of the definition, but the degraded usefulness of this unit at high beam energies was mentioned in the accompanying text. In the meantime, the new concept of roentgen equivalent man (rem
The kilogram or kilogramme is the base unit of mass in the International System of Units. Until 20 May 2019, it remains defined by a platinum alloy cylinder, the International Prototype Kilogram, manufactured in 1889, stored in Saint-Cloud, a suburb of Paris. After 20 May, it will be defined in terms of fundamental physical constants; the kilogram was defined as the mass of a litre of water. That was an inconvenient quantity to replicate, so in 1799 a platinum artefact was fashioned to define the kilogram; that artefact, the IPK, have been the standard of the unit of mass for the metric system since. In spite of best efforts to maintain it, the IPK has diverged from its replicas by 50 micrograms since their manufacture late in the 19th century; this led to efforts to develop measurement technology precise enough to allow replacing the kilogram artifact with a definition based directly on physical phenomena, now scheduled to take place in 2019. The new definition is based on invariant constants of nature, in particular the Planck constant, which will change to being defined rather than measured, thereby fixing the value of the kilogram in terms of the second and the metre, eliminating the need for the IPK.
The new definition was approved by the General Conference on Weights and Measures on 16 November 2018. The Planck constant relates a light particle's energy, hence mass, to its frequency; the new definition only became possible when instruments were devised to measure the Planck constant with sufficient accuracy based on the IPK definition of the kilogram. The gram, 1/1000 of a kilogram, was provisionally defined in 1795 as the mass of one cubic centimetre of water at the melting point of ice; the final kilogram, manufactured as a prototype in 1799 and from which the International Prototype Kilogram was derived in 1875, had a mass equal to the mass of 1 dm3 of water under atmospheric pressure and at the temperature of its maximum density, 4 °C. The kilogram is the only named SI unit with an SI prefix as part of its name; until the 2019 redefinition of SI base units, it was the last SI unit, still directly defined by an artefact rather than a fundamental physical property that could be independently reproduced in different laboratories.
Three other base units and 17 derived units in the SI system are defined in relation to the kilogram, thus its stability is important. The definitions of only eight other named SI units do not depend on the kilogram: those of temperature and frequency, angle; the IPK is used or handled. Copies of the IPK kept by national metrology laboratories around the world were compared with the IPK in 1889, 1948, 1989 to provide traceability of measurements of mass anywhere in the world back to the IPK; the International Prototype Kilogram was commissioned by the General Conference on Weights and Measures under the authority of the Metre Convention, in the custody of the International Bureau of Weights and Measures who hold it on behalf of the CGPM. After the International Prototype Kilogram had been found to vary in mass over time relative to its reproductions, the International Committee for Weights and Measures recommended in 2005 that the kilogram be redefined in terms of a fundamental constant of nature.
At its 2011 meeting, the CGPM agreed in principle that the kilogram should be redefined in terms of the Planck constant, h. The decision was deferred until 2014. CIPM has proposed revised definitions of the SI base units, for consideration at the 26th CGPM; the formal vote, which took place on 16 November 2018, approved the change, with the new definitions coming into force on 20 May 2019. The accepted redefinition defines the Planck constant as 6.62607015×10−34 kg⋅m2⋅s−1, thereby defining the kilogram in terms of the second and the metre. Since the second and metre are defined in terms of physical constants, the kilogram is defined in terms of physical constants only; the avoirdupois pound, used in both the imperial and US customary systems, is now defined in terms of the kilogram. Other traditional units of weight and mass around the world are now defined in terms of the kilogram, making the kilogram the primary standard for all units of mass on Earth; the word kilogramme or kilogram is derived from the French kilogramme, which itself was a learned coinage, prefixing the Greek stem of χίλιοι khilioi "a thousand" to gramma, a Late Latin term for "a small weight", itself from Greek γράμμα.
The word kilogramme was written into French law in 1795, in the Decree of 18 Germinal, which revised the older system of units introduced by the French National Convention in 1793, where the gravet had been defined as weight of a cubic centimetre of water, equal to 1/1000 of a grave. In the decree of 1795, the term gramme thus replaced gravet, kilogramme replaced grave; the French spelling was adopted in Great Britain when the word was used for the first time in English in 1795, with the spelling kilogram being adopted in the United States. In the United Kingdom both spellings are used, with "kilogram" having become by far the more common. UK law regulating the units to be used when trading by weight or measure does not prevent the use of either spelling. In the 19th century the French word kilo, a shortening of kilogramme, was imported into the English language where it has been used to mean both kilogram and kilometre. While kilo is acceptable in many generalist texts
A radionuclide is an atom that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation. During those processes, the radionuclide is said to undergo radioactive decay; these emissions are considered ionizing radiation because they are powerful enough to liberate an electron from another atom. The radioactive decay can produce a stable nuclide or will sometimes produce a new unstable radionuclide which may undergo further decay. Radioactive decay is a random process at the level of single atoms: it is impossible to predict when one particular atom will decay. However, for a collection of atoms of a single element the decay rate, thus the half-life for that collection can be calculated from their measured decay constants; the range of the half-lives of radioactive atoms have no known limits and span a time range of over 55 orders of magnitude. Radionuclides occur or are artificially produced in nuclear reactors, particle accelerators or radionuclide generators.
There are about 730 radionuclides with half-lives longer than 60 minutes. Thirty-two of those are primordial radionuclides. At least another 60 radionuclides are detectable in nature, either as daughters of primordial radionuclides or as radionuclides produced through natural production on Earth by cosmic radiation. More than 2400 radionuclides have half-lives less than 60 minutes. Most of those are only produced artificially, have short half-lives. For comparison, there are about 253 stable nuclides. All chemical elements can exist as radionuclides; the lightest element, has a well-known radionuclide, tritium. Elements heavier than lead, the elements technetium and promethium, exist only as radionuclides. Unplanned exposure to radionuclides has a harmful effect on living organisms including humans, although low levels of exposure occur without harm; the degree of harm will depend on the nature and extent of the radiation produced, the amount and nature of exposure, the biochemical properties of the element.
However, radionuclides with suitable properties are used in nuclear medicine for both diagnosis and treatment. An imaging tracer made with radionuclides is called a radioactive tracer. A pharmaceutical drug made with radionuclides is called a radiopharmaceutical. On Earth occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides, cosmogenic radionuclides. Radionuclides are produced in stellar nucleosynthesis and supernova explosions along with stable nuclides. Most decay but can still be observed astronomically and can play a part in understanding astronomic processes. Primordial radionuclides, such as uranium and thorium, exist in the present time because their half-lives are so long that they have not yet decayed; some radionuclides have half-lives so long that decay has only been detected, for most practical purposes they can be considered stable, most notably bismuth-209: detection of this decay meant that bismuth was no longer considered stable.
It is possible decay may be observed in other nuclides adding to this list of primordial radionuclides. Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides, they have shorter half-lives than primordial radionuclides. They arise in the decay chain of the primordial isotopes thorium-232, uranium-238 and uranium-235. Examples include the natural isotopes of radium. Cosmogenic isotopes, such as carbon-14, are present because they are continually being formed in the atmosphere due to cosmic rays. Many of these radionuclides exist only in trace amounts in nature, including all cosmogenic nuclides. Secondary radionuclides will occur in proportion to their half-lives, so short-lived ones will be rare, thus polonium can be found in uranium ores at about 0.1 mg per metric ton. Further radionunclides may occur in nature in undetectable amounts as a result of rare events such as spontaneous fission or uncommon cosmic ray interactions. Radionuclides are produced as an unavoidable result of nuclear thermonuclear explosions.
The process of nuclear fission creates a wide range of fission products, most of which are radionuclides. Further radionuclides can be created from irradiation of the nuclear fuel and of the surrounding structures, yielding activation products; this complex mixture of radionuclides with different chemistries and radioactivity makes handling nuclear waste and dealing with nuclear fallout problematic. Synthetic radionuclides are deliberately synthesised using nuclear reactors, particle accelerators or radionuclide generators: As well as being extracted from nuclear waste, radioisotopes can be produced deliberately with nuclear reactors, exploiting the high flux of neutrons present; these neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is iridium-
Pierre Curie was a French physicist, a pioneer in crystallography, magnetism and radioactivity. In 1903, he received the Nobel Prize in Physics with his wife, Marie Skłodowska-Curie, Henri Becquerel, "in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel". Born in Paris on 15 May 1859, Pierre Curie was the son of Eugene Curie, a doctor of French Huguenot Protestant origin from Alsatia, Sophie-Claire Depouilly Curie, he was educated by his father and in his early teens showed a strong aptitude for mathematics and geometry. When he was 16, he earned his math degree. By the age of 18, he had completed the equivalent of a higher degree, but did not proceed to a doctorate due to lack of money. Instead he worked as a laboratory instructor; when Pierre Curie was preparing for his bachelor of science degree, he worked in the laboratory of Jean-Gustave Bourbouze in the Faculty of Science. In 1880 Pierre and his older brother Jacques demonstrated that an electric potential was generated when crystals were compressed, i.e. piezoelectricity.
To aid this work they invented the piezoelectric quartz electrometer. The following year they demonstrated the reverse effect: that crystals could be made to deform when subject to an electric field. All digital electronic circuits now rely on this in the form of crystal oscillators. In subsequent work on magnetism Pierre Curie defined the Curie scale; this work involved delicate equipment - balances, etc. Pierre Curie was introduced to Maria Skłodowska by physicist Józef Wierusz-Kowalski. Curie took her into his laboratory as his student, his admiration for her grew. He began to regard Skłodowska as his muse, she refused his initial proposal, but agreed to marry him on 26 July 1895. It would be a beautiful thing, a thing I dare not hope, if we could spend our life near each other, hypnotized by our dreams: your patriotic dream, our humanitarian dream, our scientific dream; the Curies had a happy, affectionate marriage, they were known for their devotion to each other. Prior to his famous doctoral studies on magnetism, he designed and perfected an sensitive torsion balance for measuring magnetic coefficients.
Variations on this equipment were used by future workers in that area. Pierre Curie studied ferromagnetism and diamagnetism for his doctoral thesis, discovered the effect of temperature on paramagnetism, now known as Curie's law; the material constant in Curie's law is known as the Curie constant. He discovered that ferromagnetic substances exhibited a critical temperature transition, above which the substances lost their ferromagnetic behavior; this is now known as the Curie temperature. The Curie temperature is used to study plate tectonics, treat hypothermia, measure caffeine, to understand extraterrestrial magnetic fields. Pierre Curie formulated what is now known as the Curie Dissymmetry Principle: a physical effect cannot have a dissymmetry absent from its efficient cause. For example, a random mixture of sand in zero gravity has no dissymmetry. Introduce a gravitational field, there is a dissymmetry because of the direction of the field; the sand grains can'self-sort' with the density increasing with depth.
But this new arrangement, with the directional arrangement of sand grains reflects the dissymmetry of the gravitational field that causes the separation. Curie worked with his wife in isolating radium, they were the first to use the term "radioactivity", were pioneers in its study. Their work, including Marie Curie's celebrated doctoral work, made use of a sensitive piezoelectric electrometer constructed by Pierre and his brother Jacques Curie. Pierre Curie's 1898 publication with his wife Mme. Curie and with M. G. Bémont for their discovery of radium and polonium was honored by a Citation for Chemical Breakthrough Award from the Division of History of Chemistry of the American Chemical Society presented to the ESPCI ParisTech in 2015. Curie and one of his students, Albert Laborde, made the first discovery of nuclear energy, by identifying the continuous emission of heat from radium particles. Curie investigated the radiation emissions of radioactive substances, through the use of magnetic fields was able to show that some of the emissions were positively charged, some were negative and some were neutral.
These correspond to alpha and gamma radiation. The curie is a unit of radioactivity named in honor of Curie by the Radiology Congress in 1910, after his death. Subsequently, there has been some controversy over whether the naming was in honor of Pierre, Marie, or both. In the late nineteenth century, Pierre Curie was investigating the mysteries of ordinary magnetism when he became aware of the spiritualist experiments of other European scientists, such as Charles Richet and Camille Flammarion. Pierre Curie thought systematic investigation into the paranormal could help with some unanswered questions about magnetism, he wrote to his fiancée Marie: "I must admit that those spiritual phenomena intensely interest me. I think in them are questions that deal with physics." Pierre Curie's notebooks from this period show. He did not attend séances such as those of Eusapia Palladino in Paris in 1905–6 as a mere