The Mars Retrograde effect.

[The_Sonarman]

An interesting chart of the Mars retrograde effect. I wonder how the ancients explained this.

http://antwrp.gsfc.nasa.gov/apod/ap060422.html

[Wolfcounsel]

Something tells me the ancients must have observed the elliptical paths of the planets around the sun and figured out the retrograde "orbits". Probably all this knowledge was lost in the destruction of the Library of Alexandria.

[Popperite]

Something tells me the ancients must have observed the elliptical paths of the planets around the sun and figured out the retrograde "orbits". Probably all this knowledge was lost in the destruction of the Library of Alexandria.

Apparantly according to the ancients, who believed the planets revoled round the earth, the planets were making epicycles while circling the earth, something like this: (from wikipedia)

http://upload.wikimedia.org/wikipedia/commons/thumb/2/29/Ptolemaic_elements.svg/250px-Ptolemaic_elements.svg.png

It was not until Copernicus that it was realised this was an optical illusion.

[ThomasMore]

Apparantly according to the ancients, who believed the planets revoled round the earth, the planets were making epicycles while circling the earth, something like this: (from wikipedia)

http://upload.wikimedia.org/wikipedia/commons/thumb/2/29/Ptolemaic_elements.svg/250px-Ptolemaic_elements.svg.png

It was not until Copernicus that it was realised this was an optical illusion.

I believe Popperite is correct.

[Wolfcounsel]

Copernicus came after the Library of Alexandria was destroyed, and that's what I meant, that the ancients (before Copernicus) probably knew about this "illusion", and recorded the data, all lost forever (?). Has anybody dug 'way down below the Great Pyramid? Never mind. It's hot today and the beer is ice-cold.:evilgrin:

[ThomasMore]

It's hot today and the beer is ice-cold.:evilgrin:

Have one for me.

[Wolfcounsel]

One ice-cold Tecate coming up.

[Popperite]

Copernicus came after the Library of Alexandria was destroyed, and that's what I meant, that the ancients (before Copernicus) probably knew about this "illusion", and recorded the data, all lost forever (?). Has anybody dug 'way down below the Great Pyramid? Never mind. It's hot today and the beer is ice-cold.:evilgrin:

The person who wrote about this, Ptolemy, lived in Alexandria in the days that the library was still around, so he probably would have had access to it. He compiled many older Greek and other astronomical works and extended on them. He came up with the epicycles as far as I know.

No hot weather here......:crazy:

[DoctorDoom]

Here's an excellent animation that makes the cause easy to understand.

<center><img src="http://img.photobucket.com/albums/v349/DocDoom777/MarsRetrograde.gif" /></center>

Source: Motions of Heavenly Bodies (http://www.physics.hku.hk/~nature/CD/regular_e/lectures/chap02.html)

[Popperite]

Here's an excellent animation that makes the cause easy to understand.
Source: Motions of Heavenly Bodies (http://www.physics.hku.hk/~nature/CD/regular_e/lectures/chap02.html)

Thanks for finding that. That's great!