Talk:Elliptic orbit

message: The animation of the three body system is good but more complicated than needed.  I think an animation of a two body system would help explain the mechanics in a simpler and better way.90.205.123.233 (talk) 10:07, 5 January 2011 (UTC)
thread_title:  Animated two body problem 

message: I edited the orbital parameters section (previously it was only a stub template), but I don't know how readable it is. The way I see it, anything is better than saying "This section is a stub. You can help by adding to it." Anyways, if you think it isn't clear, please rewrite it to make it clearer. NHammen 19:38, 5 August 2006 (UTC)
thread_title:  Orbital parameters 

message: The figure appears to be broken.192.160.51.70 13:04, 13 September 2006 (UTC)
thread_title:  Figure? 

message: I think this article should be radically rewritten
It should say:
"An elliptic orbit is a Kepler orbit with the eccentricity greater than 0 and less than 1."
It is fine to have a figure with an elliptic orbit but do not write "planet/Sun" on a highly eccentric orbit. Comet/Sun or Spacecraft/Earth would be better!
Nice to have a moving picture but not "Two bodies with similar mass". Does not exist in the Solar system!
It is true that the total energy is :-\frac{\mu}{2 \cdot a}, "vis viva", 
But why the conclusion:
*Velocity does not depend on eccentricity but is determined by length of semi-major axis (a\,\!),
*Velocity equation is similar to that for hyperbolic trajectory with the difference that for the latter, {1\over{2a}} is positive.
Strange conclusion!
The correct formulas for velocity can be found in Kepler orbit article
The formula
:T={2\pi\over{\sqrt{\mu}}}a^{3\over{2}}
derived in Kepler orbit article
Under heading "Energy" the same "vis viva" is repeated
:{v^2\over{2}}-{\mu\over{r}}=-{\mu\over{2a}}=\epsilon<0 
Kepler orbit covers "elliptic orbit" but I think it is OK with a short separate article with a picture of an ellips. There should be arrows to "apocentre" and "pericentre" to cover those words too!
I think there should be 3 standardized articles for elliptic, parabolic and hyperbolic orbits with picture (moving!) and apsis marked. With reference to the Kepler orbit article where all details for all 3 types of orbits are derived!  —Preceding unsigned comment added by Stamcose (talk • contribs) 15:32, 12 July 2008 (UTC)
thread_title:  Improvement 

message: From the first paragraph, should
"Homanice transfer orbit,"
be Hohmann transfer orbit?
210.49.253.179 (talk) 23:59, 17 March 2009 (UTC)
thread_title:  Hohmann transfer? 

message: A specific explanation of why the planets move in eliptical orbits rather than circular orbits would be great. Wapondaponda (talk) 02:52, 4 June 2009 (UTC)
thread_title: Explanation

message: For an orbit to be an ellipse doesn't the end point have to meet up with the starting point? Given earth is always in more or less a forward motion (sometimes faster than the sun and sometimes a little slower) how can an elopes be formed? If I try draw it on paper with a very rough inaccurate representation of motion of the sun planets solar system and galaxy I end up with a squiggle that never crosses its previous path at all. A simple experiment to prove the point. While in a moving car spray paint an ellipse on the fence as you are moving. ZhuLien 66.249.80.203 (talk) 16:22, 12 March 2014 (UTC)
replies: text: You are right. BUT! For the purposes of orbit calculation you can declare the Earth to be stationary or the Sun to be stationary. (Remember the Sun is orbiting the Galaxy at 250 km/s.) This gives you the classic elliptical or hyperbolic orbit. Then if you want, you can consider the movement of the parent body. So for an Earth satellite you calculate assuming the Earth is stationary then you can change your Frame of reference by assuming that the Sun to be stationary and the Earth to be moving at 30 km/s. That changes the ellipse into a cycloid. As an example if we consider the Moon to be in orbit round the Earth then it traces an ellipse about every 29 days. To this we can add various perturbing factors such as Earth not being perfectly spherical and the gravitational effects of raising tides on a rotating planet and we can get a very accurate picture. We could note that Earth-Moon together rotate about their Barycenter - a point 4761 km from the Earth's center - but changing the frame too early just makes the detailed calculations more complex. If you took a Sun-centered approach then the Moon's orbit becomes a near perfect ellipse with 26 tiny wiggles - 13 towards the Sun and 13 away. But the wiggles are too small to be detected by looking. If you drew the orbit on a large sheet of graph paper (1m square say) the wiggles would be less than the thickness of the pencil line defining the orbit but these wiggles are everything we see when we consider the Earth-Moon orbiting system.OrewaTel (talk) 09:49, 20 July 2020 (UTC)
thread_title:  elliptical? 

message: I think elliptical is preferred over elliptic. Bubba73 You talkin' to me? 01:32, 18 September 2014 (UTC)
thread_title:  elliptical or elliptic? 

message: From Kepler's Laws and the geometry of the ellipse, it can be shown that
P = [2(pi)ab]/[pv]
where P=period, a=semi-major axis, b=semi-minor axis, p=perihelion distance, v=orbital speed at p.
Alternatively, qv can be used, with q=aphelion distance, v=orbital speed at aphelion. Eroica (talk) 15:36, 28 April 2016 (UTC)
thread_title:  Orbital Speed and Other Parameters 

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thread_title:  External links modified 

message: This page suffers from the following common Wikipedia issue (highlighted in Why Wikipedia is not so great: Readability and writing style):
* Many Wikipedians write in a way that is considered acceptable within the author's peer group, but is less comprehensible to the general reader. This may include the use of jargon.
This article consists almost entirely of jargon or non-contextualized formulae, such that it provides little value to anyone who is not already an astronomy expert. It is not until section 7 (Solar System) before there is anything comprehensible to the average reader and that turns into gibberish (to everyone) by the second sentence, as it references 'both bodies' when 2 bodies have not been introduced and only gets more incomprehensible from there (I imagine someone edited the first sentence without bothering to confirm that the paragraph as a whole still made sense).
The one saving grace of this page is the graphic of a small body orbiting a large one at the top of the page. It is extremely helpful in answering a number of the reader's most likely questions and providing a visual and intuitive understanding of elliptic orbit.
Almost all of the formulae and technical jargon needs to be moved down the article and several sections introduced which offers some insight into the reader's most likely question, namely: Why do planets (and other bodies) have an elliptic orbit in the first place? This should be comprehensively explained before diving into computations of velocity, orbital period, or energy. The technical definition from the first paragraph can be left in the opening section, but needs to come after a coherent explanation of elliptic orbit. The second paragraph about the 'gravitational two-body problem with negative energy' should maybe be removed entirely, as it illuminates little and the reader has to do some serious digging through multiple links to comprehend what that even means.--BrianMakesEdits (talk) 06:39, 2 April 2019 (UTC)
thread_title:  Audience 

message: It should be STRONGLY noted under the "File:Animation of Orbital eccentricity.gif" image that it is not possible for a planet to change from one of these orbits to another. That is, a planet cannot maintain its semi-major axis and change its eccentricity. To do so has no change in orbital energy. That means it takes no work to do so. So, if it ever happened, it would mean than orbits could spontaneously evaporate. That is, they could transition from a circular orbit to a parabolic one without any work done on it. That just isn't possible.
See the book "Air of Doubt" (airofdoubt.com) for the correct way to model orbits with a time-dependent Hamiltonian.  — Preceding unsigned comment added by AoDFT (talk • contribs) 21:51, 27 October 2020 (UTC)
thread_title:  Multiple eccentricity, single semi-major axis animation needs a caption.