Brightness of Mars as observed from earth

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Discussion Overview

The discussion revolves around the brightness of Mars as observed from Earth, particularly during its opposition. Participants explore explanations for this phenomenon using both the Ptolemaic and Copernican models of the solar system, considering the implications of each model on the perceived brightness of Mars.

Discussion Character

  • Homework-related
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant notes that Mars appears brighter during opposition due to its proximity to Earth.
  • Another participant mentions the use of epicycles in the Ptolemaic model and suggests that the Earth’s position affects Mars's brightness.
  • A later reply questions the reasoning behind the brightness related to the deferent and epicycle system in the Ptolemaic model, prompting a consideration of other factors that may influence brightness.
  • One participant concludes that retrograde motion contributes to Mars appearing brighter during opposition, although this claim is not universally accepted or elaborated upon.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confusion regarding the models and their implications. There is no clear consensus on the explanations provided, and some points remain contested or unclear.

Contextual Notes

Participants reference specific aspects of the Ptolemaic model, such as epicycles and deferents, but do not provide detailed mathematical or graphical representations to support their claims. The discussion lacks resolution on how these models specifically account for the observed brightness of Mars.

lebbo
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it is observed that Mars is somewhat brighter when in opposition (ie. sun- Earth - Mars in that order) that at other times. How can this be explained using
a) The Ptolemaic model and
b) The Copernican model of the solar system.
(Assume that Ptolomy's construction describes the actual motion of the planet)

can some one give me some sites and also an explanation
 
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lebbo said:
it is observed that Mars is somewhat brighter when in opposition (ie. sun- Earth - Mars in that order) that at other times. How can this be explained using
a) The Ptolemaic model and
b) The Copernican model of the solar system.
(Assume that Ptolomy's construction describes the actual motion of the planet)

These sound an awful lot like homework problems. If so, you need to show some attempts before we can help you.
 
ok
In both models Mars is closest to Earth at opposition
and i know that ptolemaic model use epicycles
also that Earth is always in the middle of the sun and Mars which makes it brighter i think i m really confused on this question
 
In the Ptolemaic (actually Apollonian/Hipparchan) model the deferent of Mars is just a circle around the Earth as center(did they do deferents in your class?). So the position of the mars's epicycle on its deferent can't be the reason Mars is closer to the Earth at opposition (why? Draw a diagram.). What other degree of freedom does the deferent/epicycle system have? Whatever it might be it's a good place to look for the answer.
 
thanks iv got it now, the retrograde causes Mars to get brighter when in oppostion of the sun and earth
 
Last edited:

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