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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

azot
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    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? – GremlinWranger Feb 27 '21 at 02:57
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    @GremlinWranger no, there is nothing else to be said. – Organic Marble Feb 27 '21 at 03:16
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    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? – uhoh Feb 27 '21 at 03:19
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    @azot your false premises are becoming too regular. "weird position" (not), "mysterious flash on the surface" (not and not). "different color of the sky" "apparently stopped" was okay because it does appear that way, but that should not have been taken as an example that the more shocking the premise, the better the question. – uhoh Feb 27 '21 at 03:22
  • All four cables should be parallel to each other no matter where the skycrane camera is located. – azot Feb 27 '21 at 03:24
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    @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. – uhoh Feb 27 '21 at 03:25
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    A standard "tell" of moon hoaxers is the repeated arguments in comments rather than asking a question and letting others answer. They want to push a specific answer by asking a question, and to push a false answer they must use a false premise in the question. It is starting to feel like this is what's happening here. – uhoh Feb 27 '21 at 03:28
  • I posted another image showing that, in a picture, real parallel lines look parallel no matter where the camera is placed. – azot Feb 27 '21 at 03:38
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    I'm going to start voting to close all these Mars-hoaxer questions as off topic. – Organic Marble Feb 27 '21 at 03:39
  • @ azot - if you are genuinely curious, make a model with some suitably straight objects poking up based on the upwards looking camera view, and take a photo looking down between them. – GremlinWranger Feb 27 '21 at 03:39
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    This is vandalism. Somebody with sock puppets started to vote for closing all my questions. I got at least ten votes for closing in a matter for 2-3 minutes. – azot Feb 27 '21 at 03:44
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    A question simply noting that the three support cables don't appear to converge to a vanishing point but seem parallel in the image, while the other cable is at a very different angle in the image would be fine. You can ask if the three support cables are parallel or not in 3D (they might not be!) and then wait for answers. Instead you are pushing your answer within your question and comments. That's the problem and that's what attracts rapid down voting and close voting for this reason. – uhoh Feb 27 '21 at 03:51
  • Be nice. Sure, there is a misconception in the question, but that is all the more reason to write an answer. A good answer will relate what we see in the picture with Perseverence's design, so there is definitely a connection to space exploration here. Please try harder to make the question work, instead of being critical of it. – DrSheldon Feb 27 '21 at 03:52
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    @DrSheldon no answer possible since the question is trying to drive a specific answer (that the video is false somehow). Can you see a good-faith question here? If you can, and can understand it, can you help articulate it? – uhoh Feb 27 '21 at 03:53
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    @azot: Would you mind if I edited the question to address some of the concerns that others have? – DrSheldon Feb 27 '21 at 03:58
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    @azot maybe dont make bad questions and people will start liking them. – Topcode Feb 27 '21 at 04:44

3 Answers3

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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.

Schwern
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    I am impressed by your effort! +1 – DrSheldon Feb 27 '21 at 04:02
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    I like your answer better :-) – uhoh Feb 27 '21 at 04:08
  • 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! – azot Feb 27 '21 at 05:33
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    @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. – Schwern Feb 27 '21 at 05:45
  • If the cables are not parallel then the angles between them are normal. – azot Feb 27 '21 at 06:01
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    @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. – Schwern Feb 27 '21 at 06:05
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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.

Russell Borogove
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  • 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. – azot Feb 27 '21 at 05:14
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    @azot "What I said is that parallel lines in real life look parallel, to the human brain" Are you sure about that? – Schwern Feb 27 '21 at 05:36
  • @Schwern , Yes I am sure. Just make the two rail tracks parallel and they will look like diverging. – azot Feb 27 '21 at 06:04
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    @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. – Schwern Feb 27 '21 at 06:39
  • 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. – azot Feb 27 '21 at 06:46
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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

uhoh
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  • 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. – azot Feb 27 '21 at 06:08
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    @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. – uhoh Feb 27 '21 at 06:36