Expert: Courtney Seligman - 6/3/2011

Question
Hello, You recently posted a question to Patrick Weiler in category Astronomy: QUESTION: hello..in his first law, j. kepler have declared that orbits are all elliptical.have you any idea if he (kepler) or any other scientist have explained why they are all elliptical? ANSWER: Actually it's almost impossible for any *natural* object to attain a circular orbit. There are too many variables involved, mainly the velocity of the orbiting object; that would have to be very precise. Only with careful adjustments of velocity and altitude can artificial satellites be placed in circular orbits. ---------- FOLLOW-UP ---------- QUESTION: you've generously gave your own explanation,thanks a lot, but.. francly, sirr.. you did'nt answer my principal questionhave you any idea if he (kepler) or any other scientist have explained why they are all elliptical? Unfortunately, Patrick Weiler has been unavailable to respond to your question. Your question has been moved to the question pool and may be picked up by other experts in that category. Feel free to repost your question to another expert by clicking on the link


will take place and answer, why orbits are elliptical?
thank you very much
dr.barzaq

ANSWER: Just wanted to let you know that I have not forgotten you, and am working on a page about orbital motions which will hopefully answer your question (and more). If you would like to see the current state of the page, check out http://cseligman.com/text/physics/orbitalmotion.htm. So far, all I've covered is the basic curvature of planetary orbits, provided links to discussions of conic sections and Kepler's First Law, explained (in as non-mathematical way as possible) how Newton's Laws of Motion and Gravity supposedly lead to elliptical orbits, and started a discussion of how things fall, in preparation for an explanation of why elliptical orbits are favored over circular ones (which I presume is the basic question you had in mind). The preliminary page will cover more topics than I think you wanted, but once finished it should at least contain the answer you need, as well as the answers to similar questions I have received and expect to receive. I'll let you know when it is "finished", so you don't need to check it out now, if you would rather wait until it is done; and since it will undoubtedly be more than you want in some ways, and perhaps less than you want in other ways, please feel free to ask for clarification of any points which are more confusing than helpful.

If I were free for the rest of the day, I'd hope to finish the page within the next hour or three; but I have commitments this evening which I can't ignore, so it will probably be sometime tomorrow before I can get back to you with a notice that the page is complete.

---------- FOLLOW-UP ----------

QUESTION: Hello
Thank you very much for your big heart and for your hardworking on my question
Pleas excuse me..I feel that I'm bothering you and wasting your precious  time.. so.. if this is true.. pleas feel free and forget about me and my question….
Concerning your answer you've wrote on your personal site:
In the figure below, which is a zoom out of your second figure, we can see
- the "force toward the sun (sun force of gravity) is stable and equal in all directions.. mean that no changes are possible during all the revolution of the orbiting body around the sun
- the mass of the orbiting body and the sun are stables, thus, any new or "new new" motions in such situation, physically is impossible.
(i discoverd impossible to paste the figure)
it's a zoom in of your second figure, were we can see the sun in the centre of the circular orbit and descover that the force toward sun and the new force toward sun are both 2radiant in the circle which's center is the sun
All the up mentioned take us again to the start line, to the original question "why orbits are all elliptical?
Finally.. how much I'm right if I conclude:
1- all what I'm receiving from you and from your colleagues are ,tel now , just personal point of view or suggestions
2-  since all the answers I've received contains no reference or bibliography we can conclude that in astronomy, we can't fined out the cause that makes a circular orbit transform into elliptical one
Sincerely
Dr. Barzaq

Answer
I haven't heard back from you, concerning exactly what sort of answer you are looking for. I realize that my frankness about the difficulty of obtaining certain types of answers may have discouraged you, and hope that you didn't take it the wrong way. My question now is, would you still like to be notified when I've finished the web page I'm working on about orbital (and in particular, circular vs elliptical) motions? Due to other commitments, it will be at least a week or two before I'm likely to finish, so there is no need for an immediate reply; but if I don't hear from you by the end of June I would presume that you are going to look elsewhere.