Giordano Bruno did no science and was not a scientist. Bruno was a follower of a movement called Hermetism, which was a cult that based its beliefs on documents which were thought to
have originated in Egypt at the time of Moses. These writings were linked with the teaching of the Egyptian God Thoth, the God of learning and had arrived in Italy from Macedonia in the 1460s. To followers of this cult, Thoth
was known as Hermes Trismegitus, or Hermes the thrice great. The book of Toth placed the sun at the centre of the universe. This is what Bruno followed. No science - only adoption of Hermeticism. He was jailed and executed
because the church considered him a heretic. The church wanted him to just recant his claims that Hermetism was the one true religion not because of his claims about the universe.
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From Routledge Encyclopedia of Philosophy
4 Cosmology
Bruno is best known for his championship of Copernicus in The Ash Wednesday Supper. In De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Spheres) (1543), Copernicus had argued both that the earth had its own daily rotation, and that it rotated around the sun (see Copernicus, N.). These theses challenged Aristotelian cosmology, but the force of the challenge was recognized only gradually. It was not until 1616 that De Revolutionibus was put on the Index of books forbidden by the Roman Catholic Church, and ironically, it may have been in part Bruno’s defence of Copernicus that led to this
result, for he pointed out that Copernicus’ theory was inconsistent with the standard ways of interpreting the Bible at that time. Bruno took Copernican cosmology more seriously and less metaphorically than Yates suggests when she writes
‘The sun-centred universe was the symbol of Bruno’s vision of universal magical religion, inspired by the works of "Hermes Trismegistus"’ (Yates 1982: 219). Nonetheless, it is true that Bruno showed little interest in the mathematical basis of Copernicus’ work. He criticized Copernicus for ‘being
more intent on the study of mathematics than of nature’ ([1584a] 1975: 57), a point which ties in with his other attacks on mathematics, and his emphasis on numerology in such writings as De monade. Moreover, Bruno got some of the technical details wrong, perhaps because he was drawing on the writings of a French bishop, Pontus de Tyard, who was favourable to Copernicus,
but muddled.
In both The Ash Wednesday Supper and On the Infinite Universe and Worlds Bruno makes a series of cosmological claims that owe much to Lucretius and Nicholas of Cusa. First, the universe is infinite, which means that it can have no centre, though there are many world-systems each of which may have its own centre. Second, these worlds may be inhabited. Third, the stars can be regarded as suns, that is, as self-luminous bodies, and they should not be seen as fixed on spheres. Fourth, the earth is made of the same stuff as the other worlds: there is no difference of kind between the sublunar realm and the heavenly realms, as Aristotelians argued. Finally, the celestial bodies that constitute the universe are ‘intelligent animals’ ([1584a] 1975: 46). Indeed, it is because the earth is animate that it must rotate. It has an ‘innate animal instinct’ ([1584c] 1950: 266), and there is no need to postulate extrinsic movers.
