Tycho Brahe made a model of universe where earth is at the centre and motionless whereas all other planet orbited around the sun.

I am interested to know how he came to this model? If it is because of parallax then how could he observe parallax as there was no telescope?

From here:

Brahe also noted that previous measurements of the planets, as recorded in the texts of the time, were incorrect. With his new measuring devices, he was able to record the position of the planets with the best possible accuracy for naked eye observations - ten times more accurately than people had been getting until then.

Even with his high quality observations, Brahe was not able to detect any changes in the positions of the stars over the year, which should occur if the Earth revolves around the Sun. If he had, this would have constituted direct proof of the Earth's motion. This parallax effect was not detected by astronomers until the 19th century.

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    $\begingroup$ AFAIK, parallax wasn't of much relevance for that model. Although he had no telescopes, Tycho had an observatory, Uraniborg. So he was able to compile more accurate observations of planetary positions than his predecessors. That data was subsequently vital to Kepler's determination of the orbit of Mars. $\endgroup$
    – PM 2Ring
    Jul 25, 2019 at 6:52
  • $\begingroup$ Can you explain how he observed the planets position in Uraniborg? $\endgroup$
    – user230507
    Jul 25, 2019 at 13:54
  • $\begingroup$ Take a look at Astronomical Instruments before the Telescope $\endgroup$
    – PM 2Ring
    Jul 25, 2019 at 14:10
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    $\begingroup$ Brahe improved instruments used for astronomical measurements. He also made much bigger instruments which helped him make more accurate observations. $\endgroup$
    – Natsfan
    Jul 25, 2019 at 22:33
  • $\begingroup$ One reason I can't understand why Tycho Brahe thought all planets(except Earth) revolve around the sun $\endgroup$
    – user230507
    Jul 28, 2019 at 19:07

2 Answers 2


Tycho Brahe's model was based on the religious beliefs of the time and the limited observations available. Other astronomers of the time tried to convince Brahe to adopt a heliocentric model. According to Tycho, the idea of a rotating and revolving Earth would be "in violation not only of all physical truth but also of the authority of Holy Scripture, which ought to be paramount."[1].

Tycho acknowledged that the daily rising and setting of the Sun and stars could be explained by the Earth's rotation, as Copernicus had said, still

"such a fast motion could not belong to the earth, a body very heavy and dense and opaque, but rather belongs to the sky itself whose form and subtle and constant matter are better suited to a perpetual motion, however fast." [2]

In 1616, Rome declared that the heliocentric model was contrary to both philosophy and Scripture, and could be discussed only as a computational convenience that had no connection to fact.[3]

  1. Repcheck, Jack (2008). Copernicus's Secret: How the Scientific Revolution Began. Simon & Schuster. ISBN 978-0-7432-8952-8.

  2. Blair, Ann (1990). "Tycho Brahe's critique of Copernicus and the Copernican system". Journal of the History of Ideas (Submitted manuscript). 51 (3): 355–377. doi:10.2307/2709620. JSTOR 2709620

  3. Russell, J. L. (1989). "Catholic astronomers and the Copernican system after the condemnation of Galileo". Annals of Science. 46 (4): 365–386. doi:10.1080/00033798900200291

  • $\begingroup$ That doesn’t really address the question of why he came up with something so different from the Ptolemaic model, which had the same “virtues” (unmoving Earth, consistency with Scripture). $\endgroup$ Jul 25, 2019 at 23:29
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    $\begingroup$ This is rather of an oversimplification. See tofspot.blogspot.com/2013/10/… for a very interesting detailed look at the issues. (Which are much more complicated and much more interesting than naive legends suggest.) $\endgroup$
    – Mark Olson
    Jul 26, 2019 at 13:46
  • $\begingroup$ @MarkOlson Thank you for that Mark. Some nice details in that blog, perhaps that should be expanded into an answer. $\endgroup$
    – userLTK
    Jul 27, 2019 at 3:30

The (Neo-)Tychonian and the Copernican/Keplerian model are actually kind of one and the same, just the location of reference changes: In the Tychonian model, you're an observer from Earth and in the Copernican you observe the system from the Sun. If you look onto the sky from Earth, you see exactly what Tycho described: The Sun and the Moon revolve around the Earth and the other planets revolve around the Sun. The Copernican model is the heliocentric point of view onto our planetary system: From the Sun it looks like the Earth rotates on its axis and revolves around the Sun.

One can use the Tychonian reference model on other planets too: E.g. from Mars it looks like the Sun and Mars' two natural satellites revolve around it and the other planets around the Sun (but the Sun itself around Mars).

So to answer your question: Tycho Brahe described and explained what we actually see, thus explaining why Mercury and Venus aren't visible while midnight, because the Ptolemaic model assumed that all planets revolve around Earth. Tycho was very wise for he explained things that are more correct than in Copernicus' model (such as comets). He knew quite exactly what our planetary system is like. His only mistake was that he thought the (fixed) stars are fixed onto the Earth rather than the Sun. The Neo-Tychonian model corrects that.

So both models can be true: either the universe revolves around the Earth (Tychonian) or Earth around its axis and the Sun (heliocentric). In order to see whether the (Neo-)Tychonian or the Copernican model is true one would have to look from outside the universe onto it. Otherwise there is probably no way to see it from interior. One can however prove or disprove the Lorentz contraction.

  • $\begingroup$ What is this "(Neo-)Tychonian" nonsense? You must be referring to Luka Popov. His work is widely ignored because it is mathematically and physically incorrect. $\endgroup$ Feb 17, 2020 at 23:41

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