Explaining Earth's Orbit Using a Geocentric Reference Frame

AI Thread Summary
The discussion revolves around explaining Earth's orbit using a geocentric reference frame, where the Earth is positioned at the center and the Sun revolves around it. Participants express confusion over the question, debating whether it refers to a true geocentric model or a geocentric reference frame. The gravitational force between the Earth and the Sun is analyzed using Newton's law of gravitation, and centripetal forces are considered for both bodies. There is a suggestion that the drawing provided reflects Ptolemaic mechanics rather than Newtonian principles. Clarification is sought on the interpretation of the question and the validity of the proposed calculations.
stunner5000pt
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Given the sun's mass (Ms = 2 x 10^30 kg) then Earth sun distnace (1.5 x 10^11 m) Newtons Constant G = 6.7 x 10^-11 Nm^2 kg^-2 use a GEOCENTRIC frame to explain the Earth's orbit (approcximate as a circle)

This was a question on my test and at first sight i was shocked.

But geocentric... if geocentric then the Earth would be at the centre and the sun would revolve around the sun. Would the sun have its own circular orbit around orbit as well?

AAANy help would be greatly appreciated!
 
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can anyone offer any kind of help with this question??

so far i have been thinking and thinking (and thinking...) i have no clue. Would the diagram for this look like the one posted here?
 

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this is my effort so farr

the force between the sun an the Earth is F_{g} = G \frac{m_{sun} m_{earth}}{r^2}

the centripetal force of the sun is F_{C1} = m_{sun} \frac{v_{1}^2}{r_{1}}

But since the sun is revolving around some axis it also experiences anotehr centripetal force F_{C2} = m_{sun} \frac{v_{2}^2}{r_{2}}

equate all those toegether when the sun is at the max distance

G \frac{m_{earth}}{r} + v_{1}^2 + v_{2}^2 = 0
and when the minimum distance is taken G \frac{m_{earth}}{r} + v_{1}^2 - v_{2}^2 = 0

thus v_{2}^2 = -v_{2}^2

thus v2 = 0?? Is this good enough?? Is this valid??

help would be greatly appreciated! :smile:
 
Last edited:
stunner5000pt said:
Given the sun's mass (Ms = 2 x 10^30 kg) then Earth sun distnace (1.5 x 10^11 m) Newtons Constant G = 6.7 x 10^-11 Nm^2 kg^-2 use a GEOCENTRIC frame to explain the Earth's orbit (approcximate as a circle)

This was a question on my test and at first sight i was shocked.

But geocentric... if geocentric then the Earth would be at the centre and the sun would revolve around the sun. Would the sun have its own circular orbit around orbit as well?

AAANy help would be greatly appreciated!
Are you sure they don't mean a geocentric reference frame? The Earth still orbits around the Sun. Your drawing is closer to geocentric theory and Ptolemaic mechanics (with its numerous epicycles and defferents) than Newtonian mechanics.
 
BobG said:
Are you sure they don't mean a geocentric reference frame? The Earth still orbits around the Sun. Your drawing is closer to geocentric theory and Ptolemaic mechanics (with its numerous epicycles and defferents) than Newtonian mechanics.
i typed out exactly waht teh question asked for

However i am pretty sure tht what was asked was the geocentric reference frame.

The drawing is mine, so don't take it as part of the question, every post after #1 is my interpretation.
 
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