Raffaello Magiotti (1597–1656) was an Italian astronomer, mathematician and physicist. Born at Montevarchi, he studied at Florence, and, having taken his vows, moved to Rome, following Cardinal Sacchetti. In 1636, he began to work at the Vatican Library. A pupil of Castelli in Rome, in 1638 he was Castelli's tip to Galileo as the candidate for the chair of Mathematics at Pisa. Well at home in the scientific community in the Papal city, Magiotti actively participated in Roman scientific debates, on which he provided detailed information to Galileo, with whom he was often in touch. During his life, Magiotti published only one work, entitled Renitenza dell’acqua alla compressione (Water's Resistance to Compression), which came out in 1648.

You can help expand this article with text translated from the corresponding article in French. (January 2012) Click [show] for important translation instructions. View a machine-translated version of the French article. Machine translation, like DeepL or Google Translate, is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Consider adding a topic to this template: there are already 6,130 articles in the main category, and specifying|topic= will aid in categorization. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing French Wikipedia article at [[:fr:Raffaello Magiotti]]; see its history for attribution. You should also add the template {{Translated|fr|Raffaello Magiotti}} to the talk page. For more guidance, see Wikipedia:Translation.

The text was the first report of the practical resistance to compression - which Magiotti mistakenly claimed to be absolute - of water at constant temperature, as well as the expansion and contraction of fluid media (water and air) subjected to changes in temperature. In addition to descriptions of various thermometers, the work also presents an illustration of the bell-jar divers, or "Cartesian devils", the discovery of which would then be attributed to the Tuscan scientist.

Magiotti played a role in the context of experimentation which preceded, and to a large extent, prepared the way, for the torricellian barometric experiments. He assisted - giving full descriptions in various letters - in the syphon experiments performed by Gasparo Berti around 1640. In a letter to Mersenne from 1648, he recalled that happy experimental period, and revealed that he had told Torricelli about the tests performed by Berti. He also suggested the use of sea-water, which is more dense than fresh water, thus making possible the decisive choice of mercury in barometric experiments. He died of the plague in 1656.^[1]