Astronomy / Space Our home planet, as seen from Mars
- Thread starter Patrick_68000
- Start date
You do not want to frighten the Martians?
You certainly don't want to upset one.
I think that's misleading as regards the distance from the earth to the moon? ie: I suspect the moon is a good way around its orbit so thus appears closer to the earth than it otherwise is?
It says so right in TFA.
You mean the article? - I actually didn't clock that link first time...
Having just read that, it implies it's even worse... It's not a single shot that gives an optical illusion, but instead two images photoshopped togethor, so the image is even more "misleading"
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I suggest you read that paragraph again then.Having just read that, it implies it's even worse... It's not a single shot that gives an optical illusion, but instead two images photoshopped togethor, so the image is even more "misleading"
What are you questioning?
The image combines two separate exposures taken on Nov. 20, 2016, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. The images were taken to calibrate HiRISE data, since the reflectance of the moon's Earth-facing side is well known. For presentation, the exposures were processed separately to optimize detail visible on both Earth and the moon. The moon is much darker than Earth and would barely be visible if shown at the same brightness scale as Earth.
The combined view retains the correct positions and sizes of the two bodies relative to each other. The distance between Earth and the moon is about 30 times the diameter of Earth. Earth and the moon appear closer than they actually are in this image because the observation was planned for a time at which the moon was almost directly behind Earth, from Mars' point of view, to see the Earth-facing side of the moon.
The combined view retains the correct positions and sizes of the two bodies relative to each other. The distance between Earth and the moon is about 30 times the diameter of Earth. Earth and the moon appear closer than they actually are in this image because the observation was planned for a time at which the moon was almost directly behind Earth, from Mars' point of view, to see the Earth-facing side of the moon.
So the image is actually not a genuine image, but made by stitching two togethor.
And, my initial point, it give an optical illusion of the moon being far closer to the Earth than it is (unlike what the article suggests?), I assume because it's well around its orbit, and therefore not at its "full distance" from Earth from that POV. eg - https://www.fourmilab.ch/earthview/figures/toscale.gif
ps: Maybe if you wrote more than half a dozen words at a time your point might be a little clearer?
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The way you formulated your comments strongly implies ill intent where there is none.
I think infact it says more about you TBH
"Ill intent"... For goodness sake!
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Fair point... But, what ever the term, reason, outcome etc...
My original (continued) point was simply that the image (most likely because of an "optical illusion") gives in incorrect impression of the distance of the moon from earth... Yes? No?
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EDIT - I had brain fade so what I wrote was risible and I have deleted it, the video was and is irrelevant anyway however I like it so it stays!
[video=youtube;OXypyrutq_M]https://www.youtube.com/watch?v=OXypyrutq_M[/video]
Sorry, I just couldn't resist.
[video=youtube;OXypyrutq_M]https://www.youtube.com/watch?v=OXypyrutq_M[/video]
Sorry, I just couldn't resist.
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I think you simply mean the image is misleading due to perspective rather than it being an optical illusion.
I think it's as simple as - in my noggin at least - the moon is probably 60 degrees through its orbit that would have isntead shown it at it's full distance from Earth, giving a better perspective on their "true" sizes and distance from each other.
ie: Had that photo been taken 5 days (?) earlier/later, the distance between the two would have been seen at its maximum, with them being something like three times further away that the image in question?
That's my point and noddy understanding of it at least...
Yerp...
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You don't get much of that at the distances involved; the diameter of the Moon's orbit is around 3‰ of the distance the image was taken at (205000Mm vs. ~750Mm), so the relative size between Earth and Moon would be fairly independent of the Moon's position.
My take on it... I like it if you get a basket ball and a tennis ball - which are approximately the right proportions for the eath and moon - and then you get someone to hold them apart to get their distance in proportion too.
Most people sort of hold them around arms length apart, but of course you need to move the tennis ball about 7+m away from the basket ball to reprisent the distance.
This look insanely too far away, until you put the icing on the cake.... Next time the moon is out (low down on the horizon), get someone to hold a tennis ball up, about 7m away from you, and with the moon in the background, bingo! They appear (about) the same size...
I recall doing that with my kids and get a Whoah... Oh yeh!
The image (above) gives no indication of this huge distance between the two objects given their size. Again I simply expect this is because the moon is well around its orbit such that the perspective is misleading, and the moon is probably well infront/behind the earth from this point of view/time.
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… and view them from about 4.5km away in this case. Foreshortening is relative to the difference in object distance in relation to their distance to the observer.
Getting away from the whole perspective thing for a moment - I have just looked at the image in wonder and showed my other half who greeted with a "yeah and". That image is taken from Mars!!!!! It is not a representation it is not an artists impression it is something made by man showing the planet of his birth from its sibling planet.
One of the reasons I love elite is my love of Sci fi - of everything from Edgar Rice Burroughs John Carter of Mars to Star trek the whole idea of being able to travel among the stars - or boldly go where no man has gone is a real living breathing thing to me. I have dreamt of a space drive being invented, of there being calls for pioneers to travel and colonise new planets just like the original Mayflower and the Americas because I would volunteer (and yes I am keeping half an eye on Musk and the "million on Mars"). OK I stand no chance of being accepted now but in years gone by it was a dream. This image is another step towards that dream - a dream I know many others share and will make happen.
One of the reasons I love elite is my love of Sci fi - of everything from Edgar Rice Burroughs John Carter of Mars to Star trek the whole idea of being able to travel among the stars - or boldly go where no man has gone is a real living breathing thing to me. I have dreamt of a space drive being invented, of there being calls for pioneers to travel and colonise new planets just like the original Mayflower and the Americas because I would volunteer (and yes I am keeping half an eye on Musk and the "million on Mars"). OK I stand no chance of being accepted now but in years gone by it was a dream. This image is another step towards that dream - a dream I know many others share and will make happen.