Talk:The Blue Marble

Why Isn’t More of the Northern Hemisphere Visible?

Something that has always bothered me about this photograph:

Poles on a sphere are diametrically opposed to each other. When you’re looking at a sphere, if you see one pole at the absolute bottom of the sphere, you should therefore see the opposing pole at the absolute top.

This photograph shows the South Pole very close to the bottom of the sphere; perhaps 15-20 degrees away from it, at most, since the absolute bottom still seems covered by Antarctica. Therefore, I’d expect the top of the sphere to show more of the area closer to the North Pole - 15 to 20 degrees away from it – which, in this hemisphere, would be Siberia, or the northern reaches of Europe and Asia. But the northernmost visible parts are Anatolia and the Caspian Sea – around 50 degrees away from the North Pole!

So to me, this picture looks almost as if the planet is “smaller” than it should be, relative to the sizes of the visible continents and oceans. Compare to the topographic model seen here to see what I mean.

I wonder what’s the cause of this? Is there an explanation, or am I simply looking at it wrong?

77.126.57.179 (talk) 16:02, 12 January 2009 (UTC)

It's because it was taken close enough to Earth that significantly less than half of the planet was visible. Northern Europe was beyond the horizon, so to speak. You can see how this works by playing around with this Earth Viewer. You can reduce altitude (the box next to "Alt:") and watch features on the edge of the visible disk disappear as they recede over the horizon. --Cam (talk) 02:31, 13 January 2009 (UTC)

Thanks - makes perfect sense now. Seems that even from the Moon's distance (right above the equator), it's still somewhat apparent that some areas around the poles are beyond the horizon. Not sure why I didn't think of it myself! 77.125.111.76 (talk) 16:38, 14 January 2009 (UTC)

Photographic Medium

Does anyone know what film this image was recorded on, I am assuming Eastman Kodak Kodachrome; any ideas? —Preceding unsigned comment added by 74.69.118.128 (talk) 06:31, 23 April 2008 (UTC)

The film was called "Ektachrome MS, color reversal, ASA 64" according to NASA. --Cam (talk) 06:51, 23 April 2008 (UTC)

Photogrammetric distance calculation:

I am an adjunct instructor in geosciences and a licensed land surveyor. My class in water resources used several methods to calculate the actual distance Apollo 17 was from Earth when this famous photo was taken. Available on the internet are pages of the full-frame Hasselblad images from this mission, so it is easy to print the full-frame image to the exact scale as the negative (Hasselblad images are 6 cm by 6 cm on the 70 mm film) and then to measure the pole-to-pole size of the Earth on the printed-to-scale copy of the negative. On such, the Earth pole-to-pole is about 31 mm in diameter. We know that the lens had a focal length of 80 mm and we know that the pole-to-pole diameter of the Earth is about 7,900 statute miles. Therefore, using similar-triangle geometry, the distance, X, is calculated as X/7900 miles = 80 mm / 31 mm, or X = about 20,400 statute miles to the center of the Earth. The log of Apollo 17 voice communications is also on the web, with the photo numbers inserted very closely to when in flight they were taken. Shortly after the Blue Marble was exposed, probably by Schmitt, Houston FIDO relays a distance of 18,100 nautical miles (multiply times 1.15 for statute miles). All things considered -- log, photogrammetric measurements, etc. -- coupled with uncertainties in all methods, led our class to conclude that the distance should be stated as about 20,000 statute miles from Earth. It makes little sense to try to be more precise, and it is interesting in the voice log that Schmitt and Houston some minutes later talk about being at about 20,000 nautical miles (I insert "nautical" because that is my understanding of the aviation standard for miles)and Schmitt replies "It feels like about 20,000 miles." From the voice log is a lot of environmental-conscious dialog about the views the Apollo 17 crew are seeing around the time of the Blue Marble photo, and maybe some of these should be on the Blue Marble page as well.

Rjwoodbury 20:41, 31 August 2007 (UTC) - Randy J. Woodbury, MS, LS, adjunct instructor in geosciences at SUNY Fredonia, rjwoodbury@yahoo.com, August 31, 2007

Hi, this is interesting stuff. I think the distances given in the Apollo transcripts may refer to distance to Earth's surface rather than to its center, which may suggest a revision of your estimate. Also note that at these relatively small distances from Earth, you are not able to see a full hemisphere, so the diameter of the visible part of the Earth will be less than the Earth's full diameter. --Cam 02:11, 1 September 2007 (UTC)

Yes, I agree the Mission Control communication likely refers to Earth's surface. My mention of center is only that the rough photogrammetric calculation would be to the center of a line that is nearly a pole-to-pole diameter. I agree that at 20,000 miles the full 7,900 mile diameter would not be visible (I calculate that the visible tangent-to-tangent points near the poles would be a line less than the full diameter, at about 7,700 miles, and some miles closer to the Earth's surface from its center). It would have been nice if there were 10 mm by 10 mm tick marks as on the lunar surface photos, except that it would detract from the artistry of the image, to help determine the size of the Earth on the negative more accurately. I think I'll work on this a little more, and I appreciate the constructive feedback and tentative agreement that our class thinking might be valuable in analyzing the Blue Marble nearly 35 years after it was clicked on a Hasselblad space camera. Rjwoodbury 18:47, 1 September 2007 (UTC) RJWoodbury

Working with data points given by the Public Affairs Officer (apparently as provided by FIDO, the Flight Data Officer) on the Hartwell transcript of real-time voice conversations during the relevant portion of the Apollo 17 mission, I made graphs of range and speed versus time of the spacecraft for the period bracketing the Blue Marble photograph taken at about 306 minutes into flight. From these graphs, I can quite accurately interpolate the range and speed at 306 minutes to be, as converted from the transcript units of nautical miles and feet-per-second, to have been 18,000 statute miles from the Earth's surface and traveling away from the Earth at about 10,500 statute-miles-per-hour (or about 175 statute-miles-per-minute). Further researching on the Hasselblad EL image size on the 70 mm film led me to find that the image was not the full 6 cm but likely about 56 mm (and the Hasselblad lunar surface cameras had glass plates at the film plane, for the 10 mm by 10 mm grid marks, that limited the full frame image to 54 mm). So, for a better photogrammetric analysis, the image of the Blue Marble on the actual film is likely about 29 mm rather than my first-calculated 31 mm. Further, a chord connecting the line-of-sight tangents near the poles in the photograph would be about 7,700 miles long and this chord at its center point would be 800 miles nearer the Earth's surface (closer to the Apollo 17 spacecraft) than the Earth's center. This leads to the photogrammetric equation, as previously discussed, to be more accurate as: ( 80 mm / 29 mm * 7700 statute miles ) - 3150 statute miles = 18,100 statute miles for the photo-calculated distance from the Hasselblad lens to the point on the Earth's surface shown at the center of the Blue Marble. In summary, my class and I have used interpolations from graphs of NASA-stated data on Apollo 17's range and speed near the time of the Blue Marble picture, along with photogrammetric measurements and analyses of the full-frame scanned image of the Blue Marble, to determine that an accurate statement of the distance Apollo 17 was from the Earth's surface at the time of the famous Blue Marble photograph was about 18,000 Statute Miles (or about 29,000 kilometers). We believe that the often-stated distance of 45,000 kilometers, and the occasionally-stated distance of 40,000 kilometers, stand to be corrected based on our analyses. The distance should be stated as "about 29,000 kilometers or about 18,000 statute miles." Rjwoodbury 17:22, 2 September 2007 (UTC)

I just received an email from the NASA contact at the Reference 1 NASA web page that gives us the distance on the article main page. This is what the email says, in part: "Although, I am not a scientist (I am just a data visualizer), I have validated your calculations and have determined that you are correct. The entry should read '...about 20,000 statute miles from the center of the earth.' I will make the appropriate changes." And this, in part, was my reply, with thanks: " Thanks for laboring on this on Labor Day. At Wikipedia, we've been discussing this over the last few days, and I have refined the analysis. Attached is the full discussion with the concluding recommendation: The distance should be stated as ' about 29,000 kilometers, or about 18,000 statute miles, from the surface of the Earth at the image’s center near Madagascar. ' " I'd like to thank user Cam and NASA for helping to make Wikipedia a more reliable encyclopedia. When NASA makes the change to its page, could someone make the appropriate similar change to the Blue Marble article where it cites the NASA page for the distance? Rjwoodbury 17:04, 3 September 2007 (UTC)

Hi, this is great! If NASA corrects the figure, let us know and I will definitely edit this article accordingly. I was just comparing the distances and times mentioned in Eric Hartwell's provisional Apollo 17 flight journal with those for Apollo 12 and other missions at the NASA History Division site, and based on the probable Ground Elaped Time (GET) of the photo of about 5 hours, came up with a probable figure of 15,000 to 16,000 nautical miles (17,300 to 18,400 statute miles) from Earth's surface. So we're converging around a similar figure. Of course, we can't add our original research to this article, but again, if NASA publishes something along these lines I will certainly add it to the article. --Cam 03:44, 4 September 2007 (UTC)

NASA corrected their web-published distance, cited in Reference 1, to "about 18,000 statute miles away from Earth" on September 4, 2007. I changed the distances in the article to correspond to this cited and corrected reference authority, and updated the date of retrieval for the referenced web page. Best regards to all in this process. Rjwoodbury 17:05, 4 September 2007 (UTC)

Final note, for the record: before user Cam and the rest of us worked on re-checking the actual distance, the NASA reference cited in the article listed the distance as 28,000 statute miles rather than the now-corrected 18,000 statute miles. Using the former web-published NASA distance, The Blue Marble Wikipedia page accurately cited the older source at 28,000 miles or 45,000 kilometers. As of the September 4, 2007, NASA change to the referenced web page, the NASA source and the Blue Marble article now list the distance as corrected. The old distance cited of 28,000 statute miles may (approximately) refer to another set of Earth photos taken by Schmitt later in the flight, but these are not the famous Blue Marble, as the Earth is both much smaller on the Hasselblad film for these later photos and not as fully illuminated as the Blue Marble photo. Of special interest, Dr. Schmitt is now the chair of the NASA Advisory Council for planning the next human missions to the Moon -- future chances for human-made Blue Marble photographs. Rjwoodbury 02:59, 5 September 2007 (UTC)

The article states: "Apollo 17's late-day (EST) December launch meant that the spacecraft passed over Africa during daylight hours in Africa;"

but shouldn't "late-day" be changed to night? It was launched at 05:33 Universal Time according to:

http://www.spacefacts.de/mission/english/apollo-17.htm

• It shouldn't be changed to night, 5:33 is late-day.

--Abyab 16:06, 14 May 2006 (UTC)

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I have seen a distance figure of about 25,000 miles or 40,000 km for this photo in several places. --Cam 05:12, Jan 18, 2005 (UTC)

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After editing distance to 40,000 km, found a NASA reference for 28,000 miles so I changed it to 45,000 km. Also found a NASA cite for the time of the photograph (5 hr 6 min after launch ~ 10:39 UTC). --Cam 17:21, Jan 21, 2005 (UTC)

File type?

When I downloaded the "very high res" pictures in the links, I couldn't view the files. They have no file extension after their names. Maybe instructions can be added to view the files...

         The file is compressed using gzip which is an open source compression application that can be found at www.gzip.org

wemzhou shi

Why is the photo displayed incorrectly? The original photo has the southern pole at the top (e.g. "upside-down"). See the original here: http://www.lpi.usra.edu/resources/apollo/catalog/70mm/magazine/?148 --24.137.104.16 17:54, 21 July 2005 (UTC)

Define "correctly". Aren't most humans used to seeing the north pole at (or toward) the "top" of the planet? It would make sense, then, to display the image in an orientation that has the "top" of the planet at the top of the image. —HorsePunchKid→龜 23:33, July 21, 2005 (UTC)

This is the way NASA has released it. No point in changing it. ¦ Reisio 02:01, 2005 July 22 (UTC)

The photo is upside down. I purchased a copy of this image as a poster from NASA and it has the south pole at the top. Take a look at the link I provided; it has the original orientation of the prints from the film cartridge. --24.137.104.16 23:24, 10 August 2005 (UTC)

Original Caption

One of the problems with open-source material is that "original" seems a maleable concept. The wikimedia version of the caption for this photo reads Malagasy, while my read of the NASA reference is Madagascar. Which is it and what is our intention (publishing the original "Original" or the open-source and therefore maleable "Original")?—Gaff ^ταλκ 09:05, 7 November 2005 (UTC)

• Most consistent "original" appears to be:

View of the Earth as seen by the Apollo 17 crew traveling toward the moon. This translunar coast photograph extends from the Mediterranean Sea area to the Antarctica south polar ice cap. This is the first time the Apollo trajectory made it possible to photograph the south polar ice cap. Note the heavy cloud cover in the southern hamisphere. Almost the entire coastline of Africa is clearly visible. The Arabian Peninsula can be seen at the northeastern edge of Africa. The large island off the coast of Africa is the Malagasy Republic. The Asian mainland is on the horizon toward the northeast.

NASA torrents for blue marble : next generation

I found this on digg. Maybe it should be in the article? http://visibleearth.nasa.gov/view_detail.php?id=7100

Well, the torrents are linked from [1], which is one of the first links on [2], which is linked from the article. ¦ Reisio 21:27, 4 February 2006 (UTC)

Love

• I love the picture 'The Blue Marble'. It's even on my talk page (User Talk: Abyab)

--Abyab 16:04, 14 May 2006 (UTC)

Size of the earth

Earth is said to have the appearance of a child's marble in the photo; that is the Earth has the same aspect at this distance as a child's marble at about arm's length.

I resurrected this from the archive. The astronauts were far enough away from earth that the earth was the size of a marble, held at arm's length. In other words, take a child's marble, and hold it in front of you. What the astronauts saw was a tiny earth which would have been eclipsed by a marble. --Ancheta Wis 08:47, 21 June 2006 (UTC)

Maybe I'm doing the math wrong, but I figure that the Earth subtends about 16 degrees at 28000 miles. If you clench your fist and stretch out your arm, your fist is about 10 degrees wide.[3] So the Earth could not have been eclipsed by a typical marble held at arm's length. --Cam 14:45, 21 June 2006 (UTC)

Your arithmetic is correct. The "size" reference has been removed from the lead-in. mdf 18:43, 14 September 2006 (UTC)

Surely it's supposed to be way bigger than a marble. The moon looks several times larger than a marble from 365 000 km away, why would a bigger Earth seem smaller for closerby ? --SonicX 0:40, 6 September 2006 (GMT+2)

Wrong caption?

Hi, as far as I know the name "Blue Marble" refers to NASA's cloudless composite satellite image of the whole Earth surface, the one accessible via this link (also provided in the external links section of the article): [4]. And I was expecting to find an article about that when I typed that in the Wikipedia search bar. Is everyone sure that this is in fact the correct name of the Apollo 17 photo? Regards, Atilim Gunes Baydin 19:49, 7 October 2006 (UTC)

Yeah, the title thing has made me a bit uncomfortable, too. I have been interested in this photo for many years, but never heard it called "The Blue Marble" until I saw this article. I'd heard people call the Earth itself a blue marble, but not this particular photo.

Sometimes Wikipedians give new names to things that don't have real-world names, or that only have obscure names. The actual correct name of the photo is the number that appears in the article. But I doubt an effort to move the article to AS17-148-22727 would succeed. --Cam 05:18, 8 October 2006 (UTC)

The name goes back to at least 1995, which probably pre-dates the Visible Earth stuff at NASA. Going further may require a trip to a real library, to look for instances of its use at the time it was originally published. mdf 13:49, 11 October 2006 (UTC)

Upside down?

I read somewhere else on wikipedia (searching for page) that the original of this image is actually the other way up, because of the spacecraft's path/orientation, and was merely rotated for publication so as not to confuse. If someone can find before I do whether this is true, perhaps a note would be useful, if we're showing it "upside down". There is no reason North should be at the top, even on a map, after all, much less a photograph. Graldensblud 12:10, 2 November 2006 (UTC)

There's a very good reason to have North at the top, on maps and on this photograph: convention. I think that the optimal response to this entire debate is to note the original orientation in the article but maintain the picture in the orientation it was published in. Ari 12:45, 2 November 2006 (UTC)

Is there any way that we can get a comparable, higher-resolution version of the original, "upside-down" image? And perhaps move it higher up on the page? While I don't think the pre-distribution rotation of the image needs more than the present mention in the text, users may find the image itself compelling. Personally, I think it best captures the truly unconventional sensation the Apollo 17 astronauts must have felt. sæ (talk) 06:50, 20 January 2008 (UTC)

I think the caption of the original, upside-down, photograph should be changed to say that "the south pole was at the top" of the picture, without referencing the north pole which is absent from the image. Also, the second appearance of the original photograph at the end of the article is redundant and should be removed. Chen. —Preceding unsigned comment added by 89.138.107.93 (talk) 08:08, 1 March 2008 (UTC)

I dont think we need to have a north-corrected and uncorrected photo. they are the same bloody photo. naturally enough you will have the same problem when you use your own camera in portait . the resulting file will default to landscape, so then you rotate it back to portrait 202.92.33.210 (talk) 05:34, 15 August 2008 (UTC)

I disagree. Not only is it an interesting fact that they were rotated 180degrees, but as to the poster above states, it gives a wonderful observation of what the astronauts may have felt 20,000 miles from home, and 'upside down'. Leave it the way it is - The 'correct image' as an addition is fine. Wikipedia at it's best. ~Daniel

Who took the picture?

If you carefully read the reference cited, you should agree that the page should not have been changed to say Cernan likely took the picture. The reference actually makes the best case for Schmitt having taken the picture, and specifically mentions that Cernan was the LEAST likely to have taken it. "Can you see it, Jack?" appears to be Cernan asking Schmitt, who now has the camera and now with the 80mm lens, if the Earth is visible on his side of the capsule. Click, click ... Could someone who can edit the main page check on this and perhaps change it back. Thanks. —Preceding unsigned comment added by 206.159.164.195 (talk) 16:19, 5 December 2007 (UTC)

Fixed today per the above observation. Indeed, Reference Citation No. 4 makes the case that Schmitt is the most likely to have been the photographer and Cernan the least likely.Rjwoodbury (talk) 00:47, 9 December 2007 (UTC)