21
$\begingroup$

What is the explanation for the apparent size difference of North America in these two photos from NASA?

Image source

Image source

$\endgroup$
7
  • 8
    $\begingroup$ Bad use of Photoshop? $\endgroup$
    – Jon Custer
    Sep 21, 2015 at 18:21
  • 2
    $\begingroup$ Not all space photos are by NASA, you know. Can you find explicit NASA sources for both images? Can you find explicit sources where NASA publicizes these two images? Otherwise, please keep your language where your facts can support it :). $\endgroup$ Sep 21, 2015 at 18:51
  • 1
    $\begingroup$ The photo is being publicized by NASA, but I can't find ANY version of it that contains specific detail of when it was take and what kind of image processing was used on it. The way it looks it's a rather skewed projection to make it look more interesting. That's fine, even though one would wish that they would tell us how it was processed. Having said that, NASA has a history of pretty poor science presentation when it comes to articles meant for the press and layman. They are too eager to please an audience that they deem too shallow to understand the real thing. $\endgroup$
    – CuriousOne
    Sep 21, 2015 at 18:57
  • 8
    $\begingroup$ Without a whit of evidence at all, the bottom one feels like it was taken at a lower altitude, with a much wider angle lens. $\endgroup$ Sep 21, 2015 at 19:12
  • 2
    $\begingroup$ @CuriousOne a google search on the image links turned up: visibleearth.nasa.gov/view.php?id=57723 and nasa.gov/multimedia/imagegallery/image_feature_2159.html which explain how the images were created from their sources, though they don't share the simulated altitude. $\endgroup$
    – Rick
    Sep 22, 2015 at 13:07

2 Answers 2

41
$\begingroup$

This is a perspective effect. In essence, the second image is taken from a lower orbit which is closer to Earth, and the Earth only looks spherical because of the use of a fisheye lens that strongly distorts the edges of the image.

This means that the field of view is a lot smaller. The Earth still looks like a circle on the page, though from close up the edges can look a bit distorted. In the second image there is no land to be distorted in the edges, and there are effects from the camera lens which can look weird to the human eye (to make the apparent sizes match you're comparing a very wide angle lens with a much narrower one). However, this effect is not photoshop magic.

(That said, the first image is, in fact, a very carefully reconstructed mosaic that is made from images taken at much lower altitudes, in a painstaking process that is explained in detail in this Earth Observatory post. It's important to emphasize that, from whatever altitude Simmon simulated, this is indeed the continental layout that you would observe with your naked eye. The original posting of this image clearly identifies it as a mosaic: NASA is always very careful to precisely label every image it publishes in a correct fashion.)

I can't find, unfortunately, the altitude that Simmons used to simulate the first image. Any brave takers care to dig through the documentation and source files to see if it's there?

The second image, referenced here, was taken by Suomi NPP from an altitude of ~830 km, from where the perspective looks roughly like this,

enter image description here

where it is obvious that the wide field of view is only possible because of the fisheye lens, with its associated distorsions.

$\endgroup$
9
  • $\begingroup$ So what you are saying is that the image is "photoshopped" albeit with scientific acuity. The statement that NASA carefully labels their images is, unfortunately, not true. You can find plenty of versions of that image which are not labeled and which are not pointing back to the source. As much as I wish NASA would be doing a good job about these things, they aren't. :-( $\endgroup$
    – CuriousOne
    Sep 21, 2015 at 19:55
  • 5
    $\begingroup$ @CuriousOne Indeed there's plenty of versions of that first picture floating around, but you cannot blame NASA if others take their pictures and crop the labels. In actual NASA material I have yet to find this (but I would be interested in examples if you have them). If anyone is irresponsible in this affair it is Apple, for choosing a composite image for a place where the public exposed to it will be misled. $\endgroup$ Sep 21, 2015 at 21:21
  • 1
    $\begingroup$ Its the aliens... Agreed perspective is a major factor in this. $\endgroup$
    – Namphibian
    Sep 22, 2015 at 0:09
  • 2
    $\begingroup$ @CuriousOne - No, it's just that the second one is faithfully replicating the equivalent of a picture taken at close range with a very wide-angle lens. See greatescapepublishing.com/… for an example. Picture 1 is the equivalent of the upper left portrait, while Picture 2 is the equivalent of the lower right. Big noses are a characteristic of this effect. $\endgroup$ Sep 22, 2015 at 2:18
  • 5
    $\begingroup$ @CuriousOne - Well, I really don't see that. What they are doing is to produce an image which looks exactly like an observer at that altitude would see. How is this a problem? Should they have tried to manipulate it so it looks more like picture 1. Is picture 1, taken from a greater altitude, more "real" than a picture taken from a different altitude? If so, how? Is the short-focal-length picure in the link less "real" than the long? If so, how? $\endgroup$ Sep 22, 2015 at 2:58
-2
$\begingroup$

The most eminent feature of the "Blue Marble" photo, the image uniformity, is not discussed in the literature, not even mentioned. The earth's image includes large areas of gas-phase – clouds, liquid-phase – oceans, and solid-phase – land, and the uniformity is nearly true for each phase separately. This feature is not compatible with Lambert's cosine law. One photo – a thousand theories.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.