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How can you explain the weird position of the communication cable in the image below?

enter image description here

The Perseverance about 20 meters above the surface of Mars. The communication cable, between the rover and its skycrane, makes a large angle with the other three cables, and looks like it comes from a totally different direction, not from the crane.

This image proves that parallel lines look parallel in a picture no matter where the camera is placed in relation to them.

enter image description here

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    $\begingroup$ Is there anything to be said here other than that the camera is on one side of the skycrane, the three lifting cables are central and the communications cable is aft so enter the frame from different directions? $\endgroup$
    – GremlinWranger
    Commented Feb 27, 2021 at 2:57
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    $\begingroup$ @GremlinWranger no, there is nothing else to be said. $\endgroup$
    – Organic Marble
    Commented Feb 27, 2021 at 3:16
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    $\begingroup$ I’m voting to close this question because it is not about Space Exploration as defined in the help center. It IS about perspective a concept which is a few thousand years old (e.g. "vanishing point") and so might be on-topic in Photography SE. However this seems to be more of a "moon landings are a hoax" question so perhaps Skeptics SE instead? $\endgroup$
    – uhoh
    Commented Feb 27, 2021 at 3:19
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    $\begingroup$ @azot That's absolutely false. They might be parallel in 3D space but not in a perspective photograph at finite distance. Please read the article to which I've linked. You are not asking questions here, you are mis-using question posts to push false narratives. $\endgroup$
    – uhoh
    Commented Feb 27, 2021 at 3:25
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    $\begingroup$ I'm going to start voting to close all these Mars-hoaxer questions as off topic. $\endgroup$
    – Organic Marble
    Commented Feb 27, 2021 at 3:39

3 Answers 3

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All four cables should be parallel to each other no matter where the skycrane camera is located. – azot

enter image description here

Maybe we can recreate this. Let's do some arts and crafts!

The support cables appear to radiate from the center of the crane, while the data cable is offset. The data cable and one support cable are attached to the rover at the same point.

enter image description here

enter image description here

If the camera is located between the support and data cable anchor points...

enter image description here

...they will appear to come from opposite sides because they are on opposite sides of the camera. Just like how parallel railroad tracks appear to converge.

enter image description here

I assure you, I received no secret government funding for this high tech simulation.

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    $\begingroup$ I am impressed by your effort! +1 $\endgroup$
    – DrSheldon
    Commented Feb 27, 2021 at 4:02
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    $\begingroup$ I like your answer better :-) $\endgroup$
    – uhoh
    Commented Feb 27, 2021 at 4:08
  • $\begingroup$ I appreciate the effort but your four cable simulators are not parallel in real life, three of them being the sides of a tetrahedron which is not the case with Perseverance! $\endgroup$
    – azot
    Commented Feb 27, 2021 at 5:33
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    $\begingroup$ @azot The sky crane's support cables are not parallel, they radiate out from a central point as I've modeled. That makes no difference to the apparent position of the data cable, it's the camera position does. The neat thing about this simple experiment is it is repeatable. Go find some string and cardboard and make whatever model satisfies you. $\endgroup$
    – Schwern
    Commented Feb 27, 2021 at 5:45
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    $\begingroup$ @azot The cables can be parallel and you'd get the same effect. It's the camera position that causes them to radiate. Try it. People have put in a lot of effort to answer your questions, your turn. Go try it. $\endgroup$
    – Schwern
    Commented Feb 27, 2021 at 6:05
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As an addendum to Schwern's excellent answer:

This image proves that parallel lines look parallel in a picture no matter where the camera is placed in relation to them.

That image proves exactly the opposite. In this picture:

enter image description here

The purple lines in the image are all parallel. The seams between the tiles in the picture, which are parallel in 3-dimensional space, are anything but parallel in the image.

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  • $\begingroup$ What I said is that parallel lines in real life look parallel, to the human brain, in a picture of them, no matter where the camera is placed. Of course they are not parallel in the photo because if they were they would no longer look like they are parallel! In the case of Perseverance, also the four cable are parallel, only three of them look parallel to each other. The fourth has a strange direction. (Your magenta lines look like some graffiti drawn over a picture by a street man. It is clear that they do not belong to the original image. $\endgroup$
    – azot
    Commented Feb 27, 2021 at 5:14
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    $\begingroup$ @azot "What I said is that parallel lines in real life look parallel, to the human brain" Are you sure about that? $\endgroup$
    – Schwern
    Commented Feb 27, 2021 at 5:36
  • $\begingroup$ @Schwern , Yes I am sure. Just make the two rail tracks parallel and they will look like diverging. $\endgroup$
    – azot
    Commented Feb 27, 2021 at 6:04
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    $\begingroup$ @azot The tracks are parallel and they appear to converge. I don't want to tell you to go stand in the middle of railroad tracks, but go find two long parallel lines, perhaps the sidelines of a football pitch, stand between them, and see for yourself. $\endgroup$
    – Schwern
    Commented Feb 27, 2021 at 6:39
  • $\begingroup$ I mean, make the two rail tracks parallel in the picture, not in reality, and they will look like diverging. The tracks will look like a railway that gradually increases its gage. $\endgroup$
    – azot
    Commented Feb 27, 2021 at 6:46
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Extended comment, not an answer:

Finite distance perspective dictates that lines which are parallel in real space will appear to meet at a vanishing point.

note that the following arguments are based on a pinhole camera (zero distortion) model. If it's a wide angle lens with plenty of distortion then all bets are off!

enter image description here

The three support cables definitely slightly converge and will likely meet at some point, they are at least consistent with being parallel to each other but it is impossible to tell if they are or not for certain.

The communications cable does not meet them at their common vanishing point, so it's almost certainly not parallel to the other three.

Any assertion that it "must be" parallel to the other three, or that it comes from some place other than the crane is simply baseless.

enter image description here

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  • $\begingroup$ The three supporting cables are not parallel in reality. They are the sides of a tetrahedron. I did not notice it. You can delete the question. I am sorry. $\endgroup$
    – azot
    Commented Feb 27, 2021 at 6:08
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    $\begingroup$ @azot once answers are posted it is nearly impossible to have a question deleted. My comments above indicate better ways to ask a question that will be better received. Everybody gets a few down-voted questions and closed questions, it's okay. It took me a while to get used to how Stack Exchange works myself. $\endgroup$
    – uhoh
    Commented Feb 27, 2021 at 6:36

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