|MadSci Network: Science History|
The answer I am to give you is maybe related more with the 'When' rather than with the 'How', but I hope you'll find it interesting anyway. It could be surprising to you but, as the other three common states of matter (solid, liquid and gaseous), the Plasma State was 'discovered' by the first human beings on Earth. This is true if you consider that 'to discover' is just to realize there's something new and unseen, even if you can't explain or understand it. Plasma State appears on Earth in three basic forms: lightning, fire and Aurora Borealis (Northern Lights). Them all are plasmas as they are made of partially ionized gases (that's what a plasma is), and were known by prehistoric humanity. Greek philosophers (400-500 B.C.) gave the first 'theory' of matter, establishing that everything was made of a mixture of four elements: Earth, Water, Air and Fire. Because of the properties they gave to those elements we could compare them with modern states of matter: Earth -> Solid State. Water -> Liquid State. Air -> Gaseous State. Fire -> Plasma State. As in many other subjects, greek philosphers made a great job on identifying and clasifying matter states and properties with nothing but their intuition and intelligence (they used no technology or experiments). But if we have to be strictly scientifical in the modern sense, the privilege of discovering the Plasma State has to be given to the English scientist W. Crookes, who, in the late-middle 19th. Century, was studying the effect and behaviour of gases at low densities when an electric discharge were forced inside a tube filled with them. He realized that a new medium appeared such that an electric current could pass through it (gas inside the tube became ionized and therefore electrically conducting, i.e. plasma were created). By then he wrote ''...The phenomenon in these exhausted tubes reveal to physical science a new world, a world where matter may exist in a fourth state ...''. So he was the first on describing an ionized gas as a new state of matter. The answer to your question would then be that the Plasma State was discovered in the 19th Century while studying electric discharges in low density gases. But the answer wouldn't be complete without mention of many other scientist who, some years later, developed Plasma Physics. First of all I should mention Irving Langmuir. He was the first on giving a complete and appropiate theory of ionized gases, and was also the first on using the name 'Plasma' to refer to this new medium or state of matter. This happened by 1920's, when some other scientists (L. Tonks, R. Seeliger, B. Klarfeld, M. Steenbeck ...) were also studying inozed gases. By that time other physicists (Saha, Chandrasekhar, Spitzer, Alfven, Houtermanns, Atkinson ...) realized the presence and importance of ionized gases in outer space, as well as the role they play in nuclear fusion reactions in star nuclei, increasing the relevance of Plasma Physics on understanding nature (as matter in stars is mainly in the plasma state, it is said that probably over 99% of matter in the whole Universe is in the plasma state). I hope this answer had been what you expected. Almost all the information I used for writting it has been extracted from the introduction to the book ''Plasma Physics'' by J.G. Linhart (North-Holland, Amsterdam - 1960). There are mountains of books devoted to the study of Plasma Physics. Almost all I know are specialized books written for physicists, so could be very hard to read. To search for more information on Plasma Physics and related topics you better surf and visit the links listed here (most of them treat Nuclear Fusion as well as Plasma Physics, as Nuclear Fusion is the main field of application of plasmas being studied nowadays): * http://fusion.gat.com/PlasmaOutreach/ (Various USA Universities and Laboratories have developed a program called 'Plasma Sciences and Technologies Education Outreach' with the aim of getting ready a place to learn about Plasma Physics and Nuclear Fusion). * http://FusEdWeb.pppl.gov/ (Princeton University Plasma Physics Laboratory) * http://www-istp.gsfc.nasa.gov/Education/whplasma.html http://astro-2.msfc.nasa.gov/academy/space/PLASMA_PHY.HTML (NASA's pages on Plasma Physics History and Theory) Enjoy... and keep on thinking.
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