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Pacemaker : Clarence W. Lillehie, Earl Bakk, U.S.A., 1957.

Paper : China, c.100 A.D.

Parachute : Louis S. Lenormand, France, 1783.

Pen : (fountain) Lewis E. Waterman, U.S.A., 1884; (ball-point) John H. Loud, U.S.A., 1888; Lazlo Biro, Argentina, 1944.

Phonograph : Thomas A. Edison, U.S.A., 1877.

Photography : (first paper negative, first photograph, on metal) Joseph Nicephore Niepce, France, 1816-1827; (discovery of fixative powers of hyposulfite of soda) Sir John Herschel, England, 1819; (first direct positive image on silver plate) Louis Dagauerre, based on work with Niepce, France, 1839; (first paper negative from which a number of positive prints could be made) William Talbot, England, 1841. Work of these four men, taken together, forms basis for all modern photography. (First color images) Alexandre Becquerel, Claude Niepce de Saint-Victor, France, 1848-1860; (commercial color film with three emulsion layers, Kodachrome) U.S.A. 1935.

Photovoltaic Effect : (light falling on certain materials can produce electricity) Edmund Becquerel, France, 1839.

Planetary Motion, Laws of : Johannes Kepler, Germany, 1609, 1619.

Plastics : (first material nitrocellulose softened by vegetable oil, camphor, precursor to Celluloid) Alexander Parkes, England, 1855; (Celluloid, involving recognition of vital effect of camphor) John W. Hyatt, U.S.A., 1869; (Bakelite, first completely synthetic plastic) Leo H. Baekeland, U.S.A., 1910; (theoretical background of macromolecules and process of polymerization on which modern plastics industry rests) Hermann Staudinger, Germany, 1922; (polypropylene and low-pressure method for producing high-density polyethylene) Robert Banks, Paul Hogan, U.S.A., 1958.

Polio, Vaccine : (experimentally safe dead-virus vaccine) Jonas E. Salk, U.S.A., 1952; (effective large-scale field trials) 1954; (officially approved) 1955; (safe oral live-virus vaccine developed) Albert B. Sabin, U.S.A. 1954; (available in the U.S.A.) 1960.
Polyvinyl Chloride (PVC) : Eugen Baumann, Germany, 1872.

Printing : (block) Japan, c.700; (movable type) Korea, c.1400, Johann Gutenberg, Germany, c.1450; (lithography, offset) Aloys Senefelder, Germany, 1796; (rotary press) Richard Hoe, U.S.A. 1844; (linotype) Ottmar Mergenthaler, U.S.A., 1884.

Printing Press, Movable Type : Johannes Gutenburg, Germany, c.1450.

Proton : Ernest Rutherford, England, 1919.

Pulsars : Antony Hewish and Jocelyn Bell Burnel, England, 1967.