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When reading this discussion I think it's important to bear in mind wp:TECH-CONTENT
May you explain why exactly you think this comet's orbit doesn't have a semi-major axis? RE your reversion titled "There is no semi-major axis at that epoch" 84.12.140.139 (talk) 02:12, 27 September 2015 (UTC)[reply]
With an eccentricity greater than 1, C/1980 E1 is on an ejection trajectory and no longer orbits the Sun. You can not use a negative semi-major axis without misleading readers. -- Kheider (talk) 13:18, 26 September 2015 (UTC)[reply]
I'm not going to accept that assertion without any evidence. The semi-major axis is one of the defining parameters of a hyperbolic orbit and you're suggesting that people would be misled by including this important information. Please state what exactly you believe the presence of this useful information will lead them to believe. The SBDB doesn't list the apoapsis because this object is on an escape trajectory, so at no point will it reach it farthest away point; I don't see what this has to do with including information on the semi-major axis though... Perhaps you are confused with the difference between the apoapsis and the semi-major axis of an orbit? 84.12.140.139 (talk) 17:09, 26 September 2015 (UTC)[reply]
Firstly, I don't think that the "average reader" will be reading an article about an obscure comet, in the same way that articles about complex numbers aren't read by average readers. Secondly, just because the correct information might be confusing is absolutely no reason to censor it. I found it far more confusing to see that the semi-major axis field was "Not Applicable" (I see that this has now been revised). 84.12.140.139 (talk) 19:02, 26 September 2015 (UTC)[reply]
(talk page stalker) Anon, listing either perihelion, semi-major axis, or aphelion (which in this case does not exist) alongside eccentricity (and four other parameters not relevant to this discussion) is sufficient to uniquely determine an orbit. Perihelion is listed, hence its orbit is uniquely determined by those values. Semi-major axis does not serve that purpose and listing a negative value, though technically correct, does not normally mean much to a reader, and hence is not useful. --JorisvS (talk) 17:54, 26 September 2015 (UTC)[reply]
In this effort to eliminate redundancy do you also propose to remove this parameter from the table on this page. I think that nearly every maths article has derived values and equations which could also be culled too! If you're so concerned that readers aren't going to be able to understand this then perhaps the negative value could link to the article on hyperbolic orbits, or have a note attached explaining this mathematical quirk. It seems arbitrary to decline including this information just because it's negative, thank goodness that the inclination is greater than zero or this might not be included too! I dispute that this value is not useful, I came to this page specifically for this information (expecting a negative value I should add). 84.12.140.139 (talk) 19:02, 26 September 2015 (UTC)[reply]
That's apples and oranges. A positive semi-major axis is very meaningful to most if not all readers. And inclination is positive—it's a value between 0 and 180°. A negative inclination is the same as a positive one with the ascending node 180° different. What did you want to do with its semi-major axis value? --JorisvS (talk) 19:10, 26 September 2015 (UTC)[reply]
Obviously the comparison to derived equations in mathematics articles was for effect, but I believe that it's inconsistent to remove the semi-major axis field here and not for every other orbit for which the periapsis or apoapsis is given. I was being flippant about the inclination. I imagine that the set of readers for whom the term "semi-major axis" is meaningful but whose brains explode on seeing a negative value there is very small indeed. Any reader who thinks that the semi-major axis for a conic section must be positive is misinformed. The page for semi-major axis doesn't say anywhere that the value must be positive, in fact in the third paragraph it specifies that the value may lie either side of zero. Every other equationfor hyperbolic orbits on Wikipedia is in terms of the (negative) semi-major axis, and not in terms of the periapsis, in fact the only equation I can find elsewhere which is written in terms of the periapsis is one to find the semi-major axis! 84.12.140.139 (talk) 19:45, 26 September 2015 (UTC)[reply]
A negative semi-major axis for hyperbolic trajectories is mathematically sound. For elliptical orbits the interpretation of the semi-major axis is straightforward: the average distance. However, this interpretation makes no sense for a negative semi-major axis. That's the big difference. --JorisvS (talk) 23:11, 26 September 2015 (UTC)[reply]
I'll ask the question more directly: what is it that you think will happen if a reader encounters a negative value for a semi-major axis when she is not expecting it; the most likely outcome I can think of is that she ends up learning something new, a worthy outcome indeed. It's worth noting that the average distance is only valid when one takes the average over the eccentric anomaly. If you consider this the sole reason for inclusion of the semi-major axis on all the elliptic orbits listed on Wikipedia I'd ask you why the semi-minor axis isn't listed as it too has every right to be the "average distance" of the orbiting body; I'd posit that the semi-major axis is included elsewhere because it's far more useful in its own right! The interpretation for the semi-major axis for elliptic orbits and hyperbolic orbits is exactly the same as the interpretation of the semi-major axis for ellipses and hyperbolas, i.e. half the distance between the intercepts of the line passing through both foci. If the little minus sign causes you so much grief, feel free to use a positive value and fly in the face of convention elsewhere... 84.12.140.139 (talk) 23:52, 26 September 2015 (UTC)[reply]
C/1980 E1 is being ejected from the Solar System. To suggest to the reader that it has an average distance of 58AU from the Sun is horribly misleading. Numerical integration shows that after 2013-Dec-24, it will *never* again be 58.268AU from the Sun. Why do you want to mislead the readers? -- Kheider (talk) 00:45, 27 September 2015 (UTC)[reply]
I think you misunderstand what the semi-major axis is used for, it has a significance far beyond the average distance of an elliptic orbit. My intention in putting this information into the article was clearly not to mislead; I decided to put it in because I myself had come looking for this information and hoped I could improve the experience of others coming after me. 84.12.140.139 (talk) 01:19, 27 September 2015 (UTC)[reply]
Your average reader will not know what a negative semi-major axis is. Without explaining "in detail" what a negative semi-major axis means, I can not see how listing an unexplained negative semi-major axis is going to help the layperson. Wikipedia readers have a hard enough time understanding that different epochs generate different orbits. -- Kheider (talk) 01:33, 27 September 2015 (UTC)[reply]
That argument could be made about innumerable topics on this website, and is no reason by itself to not include information. My suggestion earlier was to attach a note to the value either linking to Hyperbolic trajectory or Semi-major axis or even just to say "The semi-major axis of hyperbolic orbits is negative by convention" 84.12.140.139 (talk) 01:40, 27 September 2015 (UTC)[reply]
I see more of a wp:TECHNICAL issue than adding something useful to the reader. You would need to write a paragraph or more to explain why listing a semi-major axis for an object being ejected from the Solar System is useful to the infobox. I think it creates more of a problem than it solves. The article is already technical compared to most comet articles. -- Kheider (talk) 01:54, 27 September 2015 (UTC)[reply]
I disagree that that paragraph would be necessary, one doesn't see the equivalent paragraph next to the semi-major axis value on any other page. The article Semi-major axis states in the opening paragraphs that the value may be negative. A quote from wp:TECH-CONTENT sums up this discussion pretty well I think: "Wikipedia strives to be a serious reference resource, and highly technical subject matter still belongs in some Wikipedia articles. Increasing the understandability of technical content is intended to be an improvement to the article for the benefit of the less knowledgeable readers, but this should be done without reducing the value to readers with more technical background .... Making articles more understandable does not necessarily mean that detailed technical content should be removed. For instance, an encyclopedia article about a chemical compound is expected to include properties of the compound, even if some of those properties are obscure to a general reader". 84.12.140.139 (talk) 02:08, 27 September 2015 (UTC)[reply]
Again, *suggesting* to the average reader that this comet has an average distance from the Sun of 58AU is horribly misleading. It would require a detailed explanation to prevent creating more problems than it solves. -- Kheider (talk) 02:13, 27 September 2015 (UTC)[reply]
That's like saying "Listing Chlorine's atomic weight as 35.5 will bamboozle readers into thinking it has a non-integer number of baryons so we should leave it out of the article". I think if a reader doesn't understand that then they are generally savvy enough to follow the link to "Atomic Weight" or "Semi-major axis" and work it out if they're interested rather than "causing problems". It's immediately clear that a body can't have a negative distance to another. Please also read my reply to your other message containing "horribly misleading". I think that what I'm saying isn't getting through, so I'll try to leave the discussion here and wait for further comments 84.12.140.139 (talk) 02:38, 27 September 2015 (UTC)[reply]
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