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We know stars are distributed in various distances, this we know by observation. If not the earth but the stars rotate we must assume that billions of crystal s

by nyc111 5y ago

We know stars are distributed in various distances, this we know by observation. If not the earth but the stars rotate we must assume that billions of crystal spheres at different distances somehow rotate in exact coordination to trace the star trails that we observe. I don’t think there is such a huge “conspiracy” of crystal spheres to fool us.

codethief 5y ago
> We know stars are distributed in various distances, this we know by observation. How do we know? Establishing the cosmic distance ladder requires far more elaborate tools than the ones discussed here (Special and General Relativity, for instance) and the necessary measurements and observations also presume in one way or another that Earth is rotating. Even if you're only talking about stars in our immediate neighborhood for which a distance measurement merely needs the parallax effect (instead of SR or GR): In this case the parallax effects literally rests on the rotation of Earth and its orbit around the sun.
- nyc111 5y ago
  > the necessary measurements and observations also presume in one way or another that Earth is rotating. Yes, the lack of star parallaxes were the main argument offered by Tycho Brahe against a moving earth theory. When star parallaxes were observed the motion of earth was accepted. The way I understand it, to measure star parallaxes the earth must move. This is not an assumption, there is no circular reasoning. And we observe different parallaxes for different stars, meaning that stars are not all on the same distance from earth. I don't know if this is a trend like flat earthers to say that all stars are the same distance from the center of the universe? > In this case the parallax effects literally rests on the rotation of Earth and its orbit around the sun. So, this way you prove that the earth moves and stars have different parallaxes and are not all attached to a crystal sphere. I don't see a problem here.
  - sandworm101 5y ago
    Stars can still have parallaxes while bolted to the spheres. Maybe the spheres themselves wobble a little. Maybe the motion of the sun around the earth imparts a slight motion to closer spheres. The fixed stars are obviously on spheres far enough away that the sun doesn't shake them.
  - throw0101a 5y ago
    > Yes, the lack of star parallaxes were the main argument offered by Tycho Brahe against a moving earth theory. Much earlier than Brahe. Aristotle in De Caelo (Book II, part 14): > The earth, then, also, whether it move about the centre or as stationary at it, must necessarily move with two motions. But if this were so, there would have to be passings and turnings of the fixed stars. Yet no such thing is observed. The same stars always rise and set in the same parts of the earth. * http://classics.mit.edu/Aristotle/heavens.2.ii.html http://classics.mit.edu/Aristotle/heavens.2.ii.html * https://en.wikipedia.org/wiki/On_the_Heavens https://en.wikipedia.org/wiki/On_the_Heavens
  - codethief 5y ago
    > This is not an assumption, there is no circular reasoning. Of course it is an assumption. A star moving across the sky is not a proof by any means. > And we observe different parallaxes for different stars, meaning that stars are not all on the same distance from earth. No, we don't measure different parallaxes for different stars. We measure different trajectories for different stars across our night sky and then, using the assumption that Earth rotates and that it is on an orbit around the sun, we conclude that there must be a parallax effect involved in the observed trajectory of the star which we can then use to estimate its distance to us. > So, this way you prove that the earth moves and stars have different parallaxes and are not all attached to a crystal sphere. I don't see a problem here. To see that what you're referring to as "proof" is no proof at all, consider that Ptolemy's epicycles (i.e. the elaborate version of the crystal spheres) are just a Fourier series and can therefore be used to describe any periodic movement across the sky. (Without you having to know anything about whether Earth rotates or not.) For a very impressive example see https://m.youtube.com/watch?v=QVuU2YCwHjw https://m.youtube.com/watch?v=QVuU2YCwHjw .

by nyc111 5y ago

codethief 5y ago

> We know stars are distributed in various distances, this we know by observation. How do we know? Establishing the cosmic distance ladder requires far more elaborate tools than the ones discussed here (Special and General Relativity, for instance) and the necessary measurements and observations also presume in one way or another that Earth is rotating. Even if you're only talking about stars in our immediate neighborhood for which a distance measurement merely needs the parallax effect (instead of SR or GR): In this case the parallax effects literally rests on the rotation of Earth and its orbit around the sun.

nyc111 5y ago
> the necessary measurements and observations also presume in one way or another that Earth is rotating. Yes, the lack of star parallaxes were the main argument offered by Tycho Brahe against a moving earth theory. When star parallaxes were observed the motion of earth was accepted. The way I understand it, to measure star parallaxes the earth must move. This is not an assumption, there is no circular reasoning. And we observe different parallaxes for different stars, meaning that stars are not all on the same distance from earth. I don't know if this is a trend like flat earthers to say that all stars are the same distance from the center of the universe? > In this case the parallax effects literally rests on the rotation of Earth and its orbit around the sun. So, this way you prove that the earth moves and stars have different parallaxes and are not all attached to a crystal sphere. I don't see a problem here.
- sandworm101 5y ago
  Stars can still have parallaxes while bolted to the spheres. Maybe the spheres themselves wobble a little. Maybe the motion of the sun around the earth imparts a slight motion to closer spheres. The fixed stars are obviously on spheres far enough away that the sun doesn't shake them.
- throw0101a 5y ago
  > Yes, the lack of star parallaxes were the main argument offered by Tycho Brahe against a moving earth theory. Much earlier than Brahe. Aristotle in De Caelo (Book II, part 14): > The earth, then, also, whether it move about the centre or as stationary at it, must necessarily move with two motions. But if this were so, there would have to be passings and turnings of the fixed stars. Yet no such thing is observed. The same stars always rise and set in the same parts of the earth. * http://classics.mit.edu/Aristotle/heavens.2.ii.html http://classics.mit.edu/Aristotle/heavens.2.ii.html * https://en.wikipedia.org/wiki/On_the_Heavens https://en.wikipedia.org/wiki/On_the_Heavens
- codethief 5y ago
  > This is not an assumption, there is no circular reasoning. Of course it is an assumption. A star moving across the sky is not a proof by any means. > And we observe different parallaxes for different stars, meaning that stars are not all on the same distance from earth. No, we don't measure different parallaxes for different stars. We measure different trajectories for different stars across our night sky and then, using the assumption that Earth rotates and that it is on an orbit around the sun, we conclude that there must be a parallax effect involved in the observed trajectory of the star which we can then use to estimate its distance to us. > So, this way you prove that the earth moves and stars have different parallaxes and are not all attached to a crystal sphere. I don't see a problem here. To see that what you're referring to as "proof" is no proof at all, consider that Ptolemy's epicycles (i.e. the elaborate version of the crystal spheres) are just a Fourier series and can therefore be used to describe any periodic movement across the sky. (Without you having to know anything about whether Earth rotates or not.) For a very impressive example see https://m.youtube.com/watch?v=QVuU2YCwHjw https://m.youtube.com/watch?v=QVuU2YCwHjw .