User:Ahumason/sandbox

Wikipedia Article: Fixed Stars

Eudoxus

Eudoxus, a student of Plato, lived from 408-435 BC (Companion 4). A mathematician and an astronomer, he generated one of the earliest sphere-centric model of the planet systems, based on his background as a mathematician. Eudoxus’s model was heliocentric, with the earth being a stationary sphere at the center of the system, surrounded by 27 rotating spheres. (Companion 4) The farthest sphere carries the stars, which he declared to be fixed. Thus, though the stars were moved around the earth by the sphere they occupied, they did not move themselves and were therefore considered fixed. (Archives 13)

Aristotle

Aristotle, who lived from 384-322 BC (Companion 5) operated on similar ideas to Plato, yet he improved on them through his books Metaphysics and On the Heavens written around 350 BCE. (Companion 5) He claimed that all things have some way of moving, (including “heavenly bodies,” or planets,) but denies that it is a vacuum because then the objects would more much too fast and without sensical direction. (Companion 5) He stated that everything was moved by something and started exploring something similar to gravity. He was one of the first to argue (and prove) that the Earth was round, drawing on observations of eclipses and the movements of the other planets relative to the Earth.(Companion 5) He proceeded to conclude that most planets operated in a circular motion. His cosmos was geocentric, with the Earth at the center surrounded by a layer of water and air, which was in turn surrounded by a layer of fire which filled the space until the Moon. (Archives 4-5) Aristotle also proposed a fifth element called “aether,” which proposedly makes up the sun, planets, and stars. (Companion 5) However, Aristotle believed that while the planets rotate, stars remain fixed. His argument is that if such a massive body was moving, there must surely be noticeable evidence from Earth. (Mercury 29) However, one cannot hear the stars moving, nor really see their progress, so he concludes that while they may be shifted by the planets, they do not move themselves. He writes in On The Heavens,­­ “If the bodies of the stars moved in a quantity either of air or of fire…the noise which they created would inevitably be tremendous, and this being so, it would reach and shatter things here on earth.” (Mercury 31) His theory that they may be carried but do not autonomously move or rotate was widely accepted for a time.

Ptolemy

Ptolemy, 100-175 AD, (Archives 32) revolutionized ideas about the cosmos through his math models and his book Mathematical Syntaxis, also known as the Almagest. (Companion 7) Written around 150 AD, Ptolemy declared that stars placement in relation to each other and distances apart remained unchanged by the rotation of the heavens. (Archives 30) He utilized a method using eclipses to find the star distances and calculated the distance of the moon based on parallax observations. (Renaissance 106) Shortly after, he wrote a follow-up called Planetary Hypotheses. (Renaissance 106) Ptolemy touted the geocentric system, drawing greatly on traditional Aristotelian physics. (Renaissance 81) He declared that the stars are fixed within their celestial spheres, but the spheres themselves are not fixed. The rotations of the spheres thus explains the subtle movements of the constellation throughout the year. (Archives 29)

Kepler

Kepler lived from 1571-1630 (Companion 12) and was a Copernican. He was a student of Tycho Brahe from 1600-1601 (Renaissance 54) and had many writings to his name. Some major ones are Mysterium cosmographicum 1596 (Renaissance p. 81) Astronomiae pars optica (1604) (Ren 70), Dioptrice 1611 – optics of lenses (Ren 70), Harmonice mundi 1618 (Ren 71) Epitome astronomiae Copernicanae 1618 introudctory textbook for Copernican astronomy in general and Keplerian astronomy in particular. --- Kepler’s laws (REN 73)HYPERLINK Rudolphine Tables 1627 HYPERLINK – working tables from which planetary positions could be completed (Ren 75) Kepler’s laws were the tipping point to really disproving the old geocentric (Ptolemaic) cosmic theories. (AZ 81)

MISC

The studies of the heavens were revolutionized with the invention of the telescope in 1608. HYPERLINK

Summer of 1609, concept of “new device for seeing faraway things as though they were nearby”, Galileo heard and made one for himself; (renaissance 81) quickly proceeded to disprove that all heavenly bodies are smooth (aristotle’s theory) (renaissance 82) – examined constellations and determined that “fixed stars” only accounted for a small proportion of what there really was (renaissance 83-83)

What changed?

From about 1670 onwards, the stars were showing themselves to be other than fixed: pickard, Robert Hooke, Flamsteed, and others were detecting in them movements amounting to sizable fractions fo a minue of arc. (Renaissance 163)

Newton’s laws led theorists to speculate on the nature and mechanisms of the cosmos….since gravity was a universal frorce, it implied that stars could hardly be at rest but rather were moving due to their mutual attraction to one another. (Archives 114)