Francesco Sizzi, an Italian

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...

who lived during the 17th century, is credited with being the first to notice the annual movement of

sunspots Sunspots are phenomena on the Sun's photosphere that appear as temporary spots that are darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic flux that inhibit convection. ...

. He also argued against the existence of the

Galilean satellites The Galilean moons (), or Galilean satellites, are the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto. They were first seen by Galileo Galilei in December 1609 or January 1610, and recognized by him as satellites of Jupiter ...

of Jupiter, discovered by

Galileo Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...

in 1610. In 1611, he published a book
Dianoia astronomica, optica, physica, qua Syderei Nuncij rumor de quatuor planetis à Galilaeo Galilaeo mathematico celeberrimo recens perspicillì cuiusdam ope conspectis, vanus redditur. Auctore Francisco Sitio Florentino
(in Latin; approximate translation of its title: "Understanding of astronomy, optics, and physics, about a rumor in Sidereus Nuncius about the four planets seen by the very celebrated mathematician Galileo Galilei with his telescope, shown to be unfounded."). His main argument was an

astrological Astrology is a range of divinatory practices, recognized as pseudoscientific since the 18th century, that claim to discern information about human affairs and terrestrial events by studying the apparent positions of celestial objects. Dif ...

one (book page 16). In the macrocosm, there are seven planets: two favorable (''beneficas'') ones, two unfavorable (''maleficas'') ones, two luminaries, and unique Mercury, erratic and indifferent (''vagum & indifferens''). In the microcosm, the human head has seven openings: two nostrils, two eyes, two ears, and one mouth. He also noted that there are seven days in the week, seven metals, etc. Given all these corresponding sets of seven, there was clearly no place for the extra planets that Galileo had claimed to have discovered. So they do not exist.

Notes

External links

"Francesco Sizzi and Correlative Cosmologies"
17th-century Italian astronomers {{Italy-astronomer-stub