Macedonio Melloni (11 April 1798 – 11 August 1854) was an Italian

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

, notable for demonstrating that

radiant heat Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. Thermal radiation is generated when heat from the movement of charges in the material (electrons and protons in common forms of matter) is ...

has similar physical properties to those of light.

Life

Born at

Parma Parma (; egl, Pärma, ) is a city in the northern Italian region of Emilia-Romagna known for its architecture, music, art, prosciutto (ham), cheese and surrounding countryside. With a population of 198,292 inhabitants, Parma is the second m ...

, in 1824 he was appointed professor at the local

University A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United Stat ...

but was compelled to escape to France after taking part in the revolution of 1831. In 1839 he went to

Naples Naples (; it, Napoli ; nap, Napule ), from grc, Νεάπολις, Neápolis, lit=new city. is the regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 909,048 within the city's adm ...

and was soon appointed director of the

Vesuvius Observatory The Vesuvius Observatory ( it, Osservatorio Vesuviano) is the surveillance centre for monitoring the three volcanic areas of Campania, Italy: Mount Vesuvius, the Phlegrean Fields and Ischia. Founded in 1841 on the slopes of Mount Vesuvius by Fe ...

, a post that he held until 1848. In 1845, he was elected a foreign member of the

Royal Swedish Academy of Sciences The Royal Swedish Academy of Sciences ( sv, Kungliga Vetenskapsakademien) is one of the royal academies of Sweden. Founded on 2 June 1739, it is an independent, non-governmental scientific organization that takes special responsibility for prom ...

. He died at

Portici Portici (; ) is a town and ''comune'' of the Metropolitan City of Naples in Italy. It is the site of the Portici Royal Palace. Geography Portici lies at the foot of Mount Vesuvius on the Bay of Naples, about southeast of Naples itself. There i ...

, near Naples, of

cholera Cholera is an infection of the small intestine by some strains of the bacterium '' Vibrio cholerae''. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea that lasts a few days. Vomiting an ...

, aged 56.

Work

Melloni's reputation as a physicist rests principally on his discoveries in radiant heat, made with the aid of the ''thermomultiplier'', a combination of

thermopile A thermopile is an electronic device that converts thermal energy into electrical energy. It is composed of several thermocouples connected usually in series or, less commonly, in parallel. Such a device works on the principle of the thermoele ...

and

galvanometer A galvanometer is an electromechanical measuring instrument for electric current. Early galvanometers were uncalibrated, but improved versions, called ammeters, were calibrated and could measure the flow of current more precisely. A galvan ...

. In 1831, soon after the discovery of thermoelectricity by Thomas Johann Seebeck, he and Leopoldo Nobili employed the instrument in experiments especially concerned with characteristics of (in modern language)

black-body radiation Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific, continuous spe ...

transmitted by various materials. He used an optical bench fitted with thermopiles, shields and light and heat sources, such as Locatelli's lamp and

Leslie's cube Leslie's cube is a device used in the measurement or demonstration of the variations in thermal radiation emitted from different surfaces at the same temperature. Device It was devised in 1804 by John Leslie (1766–1832), a Scottish mathematicia ...

, in order to show that radiant heat could be reflected,

refracted In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...

and polarised in the same way as light. His most important book, ''La thermocrose au la coloration calorifique'' (Vol. I., Naples, 1850), was unfinished at his death. He also studied the

magnetism Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles ...

of rocks, electrostatic induction and

photography Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is emplo ...

Honours

Rumford Medal The Rumford Medal is an award bestowed by Britain's Royal Society every alternating year for "an outstandingly important recent discovery in the field of thermal or optical properties of matter made by a scientist working in Europe". First awar ...

of the

Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

(1834); *Correspondent of the

Académie des Sciences The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at ...

(1835); *Foreign member of the Royal Society, (1839).

References

{{DEFAULTSORT:Melloni, Macedonio 1798 births 1854 deaths People from Parma Deaths from cholera 19th-century Italian physicists Foreign Members of the Royal Society Members of the French Academy of Sciences Members of the Royal Swedish Academy of Sciences Recipients of the Pour le Mérite (civil class) Infectious disease deaths in Campania