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PaperclipPerfector  1mo ago (text post)   2430 thread views

Friday Fun Thread for July 19, 2024

Be advised: this thread is not for serious in-depth discussion of weighty topics (we have a link for that), this thread is not for anything Culture War related. This thread is for Fun. You got jokes? Share 'em. You got silly questions? Ask 'em.

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I recently came across this guy who wishes to RETVRN by rejecting copernicanism and embracing keplerism.

https://book.tychos.space/

Like many cranks, he takes forever to get to anything like a refutation of the established model, but in chapter 7 he finally gets there.

https://book.tychos.space/chapters/7-the-copernican-model

His argument rests on a "geometric impossibility" relating to the parallax of mars and a particular star. At first glance the diagrams seem convincing and it was not immediately clear to me where the trick was, so I thought it might be a fun exercise for others as well. My solution is in the spoiler.

Cassini's experiment involved taking an observation of mars against the stellar background at the same time from two different positions on earth. Taking an observation of mars at two different times of the year is not the same, because mars is also moving.

Imagine standing with your buddy in a field. You take a look at him with your left eye and he seems to be pretty much right under the moon. You both move about a mile to your left. You take a look at him again and he still seems to be pretty much right under the moon. At the same time, looking at your buddy with your right eye makes him noticeably but very slightly move with relation to the moon. A geometric impossibility?

Note that:

  1. the earth's orbit's diameter is about a million times smaller than the distance from earth to deneb algedi.

  2. In cassini's experiment the change of mars's position was a whopping 15 arc seconds (that's the size of a basketball hoop seen from two and a half miles away). https://astronomy.stackexchange.com/questions/46988/how-exactly-was-giovanni-cassini-able-to-measure-the-distance-to-mars

  3. the screenshot of mars and deneb algedi from earth is tiny and doesn't have any numbers, so it would be easy to round off subtle changes in position to zero.

Finally, the top down solar system diagram shows deneb algedi about 1AU from earth instead of the true distance of about a million AU. In reality, deneb algedi is so far away relative to the earth's orbit that the sun-earth-deneb algedi angle is infinitesimally smaller than 90 degrees. If the image was to scale we could clearly see that mars is simply rather close to the earth-deneb algedi line in both cases, and at the present scale there's plenty of slack to make it seem like an impossible geometry.

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