Two Different Orreries: The Tychonian vs. The Copernican Model of The Cosmos

Posted: May 18, 2017 in Uncategorized

Click the image below for link to dynamic flash showing planetary motion in the solar system. The date can be set and positions observed. There are two views or modes: Sun-based Copernican view and Earth-centric Tychonian view.

Online Orrery

Trepidation of The Spheres


Moving of th’ earth brings harms and fears ;
Men reckon what it did, and meant ;
But trepidation of the spheres,
Though greater far, is innocent.

John Donne, from “A Valediction Forbidding Mourning” (1633)

  1. Marko Miholjcic says:

    I am curious as to why the stanza from John Donne’s poem is included in this post. Perhaps this post was included to show the great interest that people had in studying the cosmos in the seventeenth century? Another theory that I have is that this post was included in order to illustrate the impact that the discoveries about the universe had on religious figures. My reasoning for this theory is that Donne was born into a devout Roman Catholic family, and was a prominent religious figure in England. Yet, he could not ignore the discoveries made about the fascinating nature of celestial bodies and had to compare his love for his partner to the stars.

    • Donne is making a comparison between earthquakes and the ‘trepidation of the spheres’; i.e., the perturbation of the planets’ orbits, according to the dominant, Ptolemaic paradigm. In keeping with this analogy, I also posted the mass by Antoine Brumel, “Ecce, Terrae Motus” (Behold, The Quaking of The Earth).

      • Marko Miholjcic says:

        That makes sense! I probably should have looked up the translation of the title of the song. The song does sound like a soundtrack that would be playing in the background of a tragic movie after an earthquake or some other natural disaster obliterates the setting.

        • Glad my brief explanation helped. The Brunel mass predates Donne by at least one hundred years. Still, both were highly curious about the phenomenon of earthquakes, each seeing them as a wonder or sign from God. You’ll note that Donne, like Milton, wrote after Galileo’s discoveries, continues to employ the old model of the cosmos. Ideas can take quite a long time to wear out. If you want to see a classic study of the remarkably slow transition from the old system to the new, see Alexandre Koyre’s “From Closed World To Infinite Universe”.

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