Short answers, pulled from the story.
The year 1453 marked a turning point when Constantinople fell to Ottoman forces. Byzantine scholars fled westward carrying precious Greek manuscripts into Italy and other parts of Europe which sparked an international search for ancient scientific texts.
Cardinal Bessarion brought a Greek manuscript from Constantinople that Regiomontanus used to complete his commentary on the Almagest. This effort laid groundwork for later Renaissance scholars who would restore these texts with unprecedented vigor after the invention of the printing press allowed faster dissemination of new ideas after 1475.
Paracelsus served as both chymist and physician during the Renaissance period believing sulphur mercury and salt formed primary alchemical principles from which all substances emerged. His ideas directly conflicted with traditional beliefs popularized by Aristotle regarding natural philosophy while recognizing that the body operated through chemical processes requiring practical medicinal applications.
De revolutionibus orbium coelestium finally published in 1543 while Copernicus lay on deathbed. Shortly before 1514 Copernicus revived Aristarchus's idea that Earth revolves around Sun and spent remaining years attempting mathematical proof supporting this heliocentric model.
Translators like Gerard of Cremona and William of Moerbeke worked from Arabic and Greek sources into Latin during the 12th century. Greatest translation efforts took place specifically within Italy attested by numerous manuscripts currently found in European libraries dating from this era.