The year 1878 in science and technology involved many significant events, listed below.
Astronomy
English astronomer Richard A. Proctor describes the Zone of Avoidance, the area of the night sky that is obscured by our own galaxy, for the first time.
Biology
Death of last confirmed Cape Lion.
Chemistry
The rare earth element holmium is identified in erbium by Marc Delafontaine and Jacques-Louis Soret in Geneva and by Per Teodor Cleve in Sweden.
Conservation
An Act of Parliament in the United Kingdom places Epping Forest in the care of the City of London Corporation to remain unenclosed.
Exploration
June 22 – Adolf Erik Nordenskiöld sets out on the year-long first navigation of the Northern Sea Route, the shipping lane from the Atlantic Ocean to the Pacific Ocean along the Siberian coast.
Geology
Clarence King publishes Systematic Geology. Charles Lapworth publishes his analysis of the change in graptolite fossils through sequences of exposed shales in southern Scotland, establishing the importance of using graptolites to understand stratigraphic sequences.
Mathematics
Belgian mathematician Victor D'Hondt describes the D'Hondt method of voting. English mathematician Rev. William Allen Whitworth is the first to publish Bertrand's ballot theorem.
Medicine
Cesare Lombroso publishes L'uomo delinquente, setting out his theory of criminal atavism. Ádám Politzer publishes Lehrbuch der Ohrenheilkunde, a major otology textbook. Dentists Act in the United Kingdom limits the title of "dentist" and "dental surgeon" to qualified and registered practitioners.
Meteorology
February 11 – The first weekly weather report is published in the United Kingdom.
Paleontology
31 Iguanodon skeletons are discovered in a coal mine at Bernissart, Belgium. The sauropod genus Diplodocus is first named by Othniel Charles Marsh as well as the Theropod genus Allosaurus. These are both from the Jurassic aged Morrison formation.
Physics
January 18 – Romanian mathematician Spiru Haret defends his doctoral thesis, which proves a result fundamental to the n-body problem in celestial mechanics.
Technology
February 19 – The phonograph is patented by Thomas Edison. The oldest known audio recording is recovered from this device in 2012. March – The 'basic' process, enabling the use of phosphoric iron ore in steelmaking, developed at Blaenavon Ironworks by Percy Gilchrist and Sidney Gilchrist Thomas, is first made public. May 22 – John Philip Holland's experimental powered submarine Holland I is launched in Paterson, New Jersey. June 15 – Eadweard Muybridge produces the sequence of stop-motion still photographs Sallie Gardner at a Gallop in California, a predecessor of silent film (capable of being viewed as an animation on a zoopraxiscope) demonstrating that all four feet of a galloping horse are off the ground at the same time. August – Cleopatra's Needle is raised onto its base in London. October 14 – The world's first recorded floodlit football fixture is played at Bramall Lane in Sheffield. December 18 – Joseph Swan of Newcastle upon Tyne in England announces his invention of an incandescent light bulb. December 31 – Karl Benz produces a two-stroke gas engine. William Crookes invents the Crookes tube which produces cathode rays. Osbourn Dorsey obtains a patent in the United States for a "door-holding device". Gustav Kessel obtains a patent in Germany for an espresso machine. Czech painter Karel Klíč perfects the photogravure process. Lester Allan Pelton produces the first operational Pelton wheel. Remington, in the United States, introduce their No. 2 typewriter, the first with a shift key enabling production of lower as well as upper case characters.
Institutions
October 1 – Virginia Polytechnic Institute and State University opens as Virginia Agricultural and Mechanical College in the United States.