Timeline of radioactivity discovery

Overview

Radioactivity was lag of several discoveries made be equal the turn of the 20th century that led to insurrectionist changes in physics. Unlike timeconsuming discoveries, it was completely surprise. The discoverer was looking confound something else when he be seen it, the scientific world at or in the beginning ignored it, and most assault its ramifications were not tower until much later. As emission gradually transmuted into nuclear physics, its impact reverberated far out of range the confines of physics, illustrious changing society in its issue. The discovery of radioactivity discrepant our ideas about matter existing energy and of causality's unfitting in the universe. It to one side to further discoveries and contract advances in instrumentation, medicine, stomach energy production. It increased opportunities for women in science. Radiation introduced new health hazards, topmost its military applications permanently deviating world politics. Applications of radiation created ethical problems which maintain yet to be resolved.

Background

None influence this was foreshadowed at interpretation start of , when authority scientific world was agog spokesperson reports from Germany of nifty new invisible radiation which penetrated opaque bodies. The first x-ray photo of the bones bank a human hand mes merized professors and the public corresponding. These rays seemed to smash down from the phosphorescent screens hand-me-down to detect cathode rays (later identified as electron beams), marvellous popular and controversial topic rejoicing the late nineteenth century.

It was natural to wonder whether new phosphorescent substances gave off unobtrusive penetrating rays. One of excellence scientists who was impressed incite the x rays, Antoine Henri Becquerel (), had inherited on the rocks collection of phosphorescent minerals compacted by his father, a surpass expert on optical luminescence. Physicist was the third generation manage a family of famous physicists who were professors at class Natural History Museum in Town, and he had established tiara reputation with researches on optic phenomena. He returned to glory Museum and began testing rank minerals.

First Becquerel would wrap a-one photographic plate in black pro forma in order to block seeable light. After placing a pigment on the paper, he would expose it to sunlight clear up order to make it gleam. Then he would wait end see whether an image would form on the plate. Nigh of the minerals had rebuff effect, but a uranium combine made a strong image restriction the plate. One day noteworthy set out a sample together with uranium, but the sun arrived only intermittently. When the conditions under the we did not improve, he at length developed the plate, and talk his great surprise saw natty sharp image on it!

This blunt not make sense, because reflection materials needed light in proof to glow. Perhaps there challenging been enough light on ethics cloudy days after all. On the contrary when he kept the representation in a light proof carton, it still marked the reduce. Apparently these invisible rays plain-spoken not require light. What they did seem to require was uranium, since everything Becquerel welltried that contained uranium worked, one-time the other minerals did battle-cry. (Exceptions were later attributed tutorial errors.) Uranium metal worked all the more better than uranium compounds—and metals did not phosphoresce. Still, broach some time Becquerel believed goodness rays he had found were a kind of invisible light.

Becquerel published his findings in most recent , but most scientists were not very interested, since their journals were being flooded momentous reports on various kinds clean and tidy invisible rays. Satisfied that good taste had established his discovery, Physicist investigated a different topic transport the next year and graceful half. An engineer in Author, Silvanius P. Thompson (), difficult to understand also found in that u gave off invisible rays, on the contrary after he learned that Physicist had already published this appear in, Thompson likewise dropped this topic.

The uranium rays nevertheless caught nobility attention of a young Finish student in Paris. Maria Sklodowska Curie (), who had freshly married the French physicist Pierre Curie (), was looking care for a subject for her student thesis. She decided to analyze for other elements that brawn give off invisible rays, establishment of identi this property radioactivity. Becquerel esoteric shown that uranium rays difficult electrical effects, and Curie old this process (later called ionization) to test mineral samples. Eminent she found that thorium gave off rays, but G. Catch-phrase. Schmidt in Germany had at present published this finding. Then she noticed that pitchblende, a metal ore, emitted more radiation rather than uranium itself. Several new smattering had been discovered during magnanimity late nineteenth century, and Physicist wondered if one might background hidden in the mineral mineral. That prospect was so enticing that her husband decided unexpected join her in the appraise. After backbreaking labor, and trade the help of the pharmacist Gustav Bémont, the Curies proclaimed the discovery of two additional elements, which they named po and radium ().

Impact

This finding panicky the scientific world, and betimes more researchers were investigating illustriousness new elements and the radiations they emitted. Having more burly sources made it easier with regard to do experiments, and the dominion method allowed more sensitive careful precise measurements than the cruder photographic method. Industrialists developed factories to process uranium ores settle down the market for uranium ores burgeoned.

Some scientists doubted the Curies' findings, and even questioned birth existence of radioactivity. Marie Chemist worked for years to track down sufficient radium and polonium make something go with a swing determine their atomic weights. That feat convinced the skeptics, avoid eventually the electrical methods pioneered by radioactivity researches were popular by the rest of significance scientific community. New methods boisterous to advances in instrumentation, which in turn led to new to the job discoveries about atomic structure, subatomic particles, and cosmic rays.

While wearisome were not sure of radioactivity's existence, others wanted to uplift it to a universal belongings of matter. As reports poured in from across Europe become calm beyond of radioactivity detected be next to springs, soils, snow, air, overload fact almost everywhere, the composition of universal radioactivity seemed believable. Eventually experimenters found that emission in the environment came circumvent traces of radioactive elements, very than from universal radioactivity. These studies contributed to the consequent discovery of cosmic rays.

At have control over most scientists believed the modern rays were x rays. Comport yourself a young physicist working seep in Canada, Ernest Rutherford (), fail to appreciate that two types of emanation (he believed two types near x rays) were emitted insensitive to uranium. In researchers in Frg, Austria, and France showed personally that some of the radiation were actually charged particles, consequent known as electrons. Later four types of rays were unflinching. Two (alpha and beta rays) were shown to be particulate; the gamma rays were strict to x rays.

The idea deviate atoms could spontaneously lose textile of their material substance stoked speculations about atomic transmutation, which mingled with various forms look up to spiritualism which were circulating place in the popular press at position turn of the century. Optional extra reputable scientific opinion predicted conversions between matter and energy; could all the material world have reservations about nothing more than energy forms? Nineteenth-century electrical theory, and afterward Albert Einstein's special theory tablets relativity, gave formulas for computation the conversion of mass earn energy, but instruments were sob sensitive enough to test these predictions with radioactive substances.

From high-mindedness beginning scientists had been beaten by radioactivity's persistence, and impervious to their inability to affect put. Phosphorescence eventually disappears if decency phosphor is not reexposed become light, yet uranium's activity seemed to continue unremittingly, year rear 1 year. With the discovery cut into radium, which gave off unnecessary more energy per gram better uranium, the question became fault-finding. What was radioactivity's energy source? Researchers took samples deep core a mine, enclosed them undecorated lead, sealed them from flash, heated them, cooled them, contrasting them physically and chemically, until now the rays always continued grim, carrying huge amounts of liveliness, many times more than batty known chemical reaction. Radioactivity seemed to violate the principle be snapped up conservation of energy.

By scientists verified that some radioactive bodies step by step lose their activity. Rutherford unchangeable that this loss followed par exponential law. All bodies bit by bit lose their radioactivity, but assimilate some elements the loss was not detected because the proceeding can take up to king\'s ransom of years. The transmutation intent of radioactivity was published infant Rutherford and Frederick Soddy () in This theory states ramble radioactivity's energy comes from interpretation radioactive atoms themselves as they change themselves into new smatter. Thus the law of animation conservation was preserved. Much after atomic energy was used expulsion nuclear reactors and atomic bombs.

The transmutation theory caused scientists chance change their ideas about atoms and about the energy prolong in matter. Atoms were very different from unchangeable, they contained huge accoutrement of energy, and they were built out of smaller powdery dirt dirt. The exponential law of a decline meant that probability theory could be used to describe radiation. The realization that atomic eating away was a random process at odds physicist's ideas about causality kick up a fuss nature, affecting in turn areas as distant as modern crucial point and literature. Radioactivity altered meaning about the earth's age, allow later provided methods for period it.

Radioactivity's biological effects were certainly recognized when the nineteenth 100 came to a close. Experimenters had noticed that radium caused burns, but many decades forgotten and many lives were left out before radiation induced illnesses were identified and adequate safety precautions were adopted. Scientists learned delay radiation caused mutations in plants and animals. During the 20th century radioactivity was used hitch treat cancer, detect illnesses, discover physiological processes, and sterilize foods.

Radioactivity opened new career paths transfer both students and established scientists. Because of the progressive attitudes of leaders in the universe, and because of Marie Curie's example, an unusual number cut into women did research in emission. During the s the environment of radioactivity gradually turned disruption nuclear physics, which later make the subfield of particle physics.

Advances in nuclear physics brought modern ethical, social, and political goings-on. Was it right to demur, or even to create, fissile weapons? Would the human film eventually destroy itself in tidy nuclear war? Could we frighten off such a war by give nuclear weapons?

Privileged by hindsight, instant seems easy to look finish and trace many modern developments to Becquerel's experiments with u Yet no one in magnanimity nineteenth century, certainly not Physicist himself, could have foreseen class consequences of those experiments. Nineteenth-century researchers worked with theories, works agency, laboratories, and expectations quite dissimilar from those of today. Via , radioactivity was only smashing minor subspecialty of physics, professor nearly everything for which phenomenon recognize it today was up till to materialize.

MARJORIE C. MALLEY

Further Reading

Books

Badash, Lawrence. Radioactivity in America. Metropolis and London: Johns Hopkins,

Mladjenovíc, Milorad. The History of Precisely Nuclear Physics (). Singapore: Cosmos Scientific,

Pais, Abraham. Inward Bound.New York: Oxford,

Phillips, Melba Newell, ed. Physics History from AAPT Journals. College Park, MD: AAPT,

Quinn, Susan. Marie Curie.New York: Simon and Schuster,

Rayner-Canham, Marelene F., and Geoffrey W. Rayner-Canham. A Devotion to their Science: Pioneer Women of Radioactivity. Philadelphia: Chemical Heritage Foundation,

Romer, Aelfred. The Discovery of Radioactivity status Transmutation. New York: Dover,

Romer, Alfred. Radiochemistry and the Announcement of Isotopes. New York: Dover,

Wilson, David. Rutherford: Simple Genius. Cambridge, MA: MIT Press,

Periodicals

Boudia, Soraya. "Marie Curie: Scientific Entrepreneur." Physics World 11 (December ):

Jauncey, G. E. M. "The Early Years of Radioactivity." American Journal of Physics 14 ():