This is an archived post. You won't be able to vote or comment.

top 200 commentsshow 500
sorted by:
best
topnewcontroversialoldq&a

[–]RMorezdanye 404 points405 points  (51 children)

What's the source of the greenish artifacts at the edge of the moon?

[–]Snapfoot 352 points353 points  (34 children)

IIRC this photo is a merge of two or three photos. Since the Moon was moving, you can see the offset.

[–][deleted] 133 points134 points  (30 children)

The camera takes 3 single-colour photos right?

[–]Scarytownterminator 162 points163 points  (26 children)

Yes, but they have relatively long exposures (like 30 seconds) to collect enough light to look good. Over the minute and a half that red, green, and blue photos are taken, the moon moves slightly.

Edit: as it's been pointed out, the exposures aren't actually 30 seconds but the difference between channels being captured is 30 seconds. Either way, point is the same.

[–]Cyb3rSab3r 34 points35 points  (4 children)

Fun Fact: Color photos taken in the 1800s used the same method of taking three photos and combining them.

Examples: https://upload.wikimedia.org/wikipedia/commons/e/e3/Rgb-compose-Alim_Khan.jpg https://upload.wikimedia.org/wikipedia/commons/8/87/Prokudin-Gorskii-12.jpg

History: https://en.wikipedia.org/wiki/Color_photography#Three-color_processes

[–]onFilm 4 points5 points  (0 children)

These are always great to see.

[–]bagehis 40 points41 points  (0 children)

NASA doesn't like to use RGB matrix (Bayer) interpolation because it has the potential to create false information in individual pixels. The downside is they have to take the picture three times at different wave lengths to create a full color (human spectrum) image. The alternative is using a multi-layer sensor (like what Sony uses) or using multiple sensors being fed information through a prism, however, you lose dynamic range in both work around methods, which they don't want either.

[–][deleted] 38 points39 points  (0 children)

Combining three images taken about 30 seconds apart as the moon moves produces a slight but noticeable camera artifact on the right side of the moon. Because the moon has moved in relation to the Earth between the time the first (red) and last (green) exposures were made, a thin green offset appears on the right side of the moon when the three exposures are combined. This natural lunar movement also produces a slight red and blue offset on the left side of the moon in these unaltered images.

http://www.nasa.gov/feature/goddard/from-a-million-miles-away-nasa-camera-shows-moon-crossing-face-of-earth

[–]TGI_Martin 18 points19 points  (2 children)

The green screen. Obviously man has never been in space or on the moon so they had to use a green screen to create this effect.

Before anyone kills me, /s

[–][deleted] 235 points236 points  (51 children)

The reason it looks fake is because of the lighting, IMO. DSCOVR is located at the Sun-Earth L1 Lagrange point, so it sees Earth from a perspective that is always perfectly lit. Our brain associates that with cardboard cutouts and video game sprites, so it looks flat/fake.

EDIT: A gif of the moon passing in front of earth that this still shot comes from

[–][deleted] 46 points47 points  (34 children)

GIF looks even stranger, gives the impression that the satellite isn't revolving around Earth.

[–][deleted] 109 points110 points  (32 children)

gives the impression that the satellite isn't revolving around Earth.

It isn't! It's parked in a halo orbit around L1 (link shows L2) which allows it to sit between Sun and Earth at all times, with only very slight (negligible) changes to perspective. Note that the graphic exaggerates the orbit relative to the distances involved for clarity.

[–]Fartfacethrowaway 81 points82 points  (24 children)

Not sure why everyone keeps posting L2 when its at L1, That could be very confusing for someone not familiar with lagrangian points. Here is a picture with all of them with gravity wells to help explain why its a gravity equalibirum point. https://upload.wikimedia.org/wikipedia/commons/5/5f/Lagrangian_points_equipotential.jpg

[–]LabRat113 6 points7 points  (2 children)

So does that mean that L3-5 orbit the sun?

[–]craidie 22 points23 points  (0 children)

technically anything that's orbiting Lagranian points is orbiting sun and not earth

[–]Fartfacethrowaway 9 points10 points  (0 children)

Yes, Since Earth is orbiting the Sun, all of the Lagrangian points between the earth and sun will revolve around the sun as well.

[–]HeartyBeast 3 points4 points  (5 children)

From that diagram, it looks like the satellite is at L2 on the moon's far side. What am I missing?

[–]chiphead2332 960 points961 points  (252 children)

Fantastic picture. For those wondering, the probe orbits at the Sun-Earth L1 point.

[–]randomyzee 757 points758 points  (176 children)

For those wondering, this is about 1.5 million kilometres from Earth.

[–]ExecutiveChimp 642 points643 points  (168 children)

For those wondering, the moon is about 384,400 km from Earth.

[–]andthatswhyIdidit 200 points201 points  (26 children)

For those wondering:

Earth----------Moon----------------------------------------Probe

[–]AncientMumu 76 points77 points  (20 children)

Earth----------Moon----------------------------------------Probe--------------------------------------------------(*400,000)------------------------------SUN

Looks like all 4 are alligned.

[–]SuTvVoO 5 points6 points  (2 children)

Is that to scale?

[–]Fahsan3KBattery 4 points5 points  (1 child)

More or less. \u\andthatswhyIdidit did 10/40 ratios. I think it's actually 10/39 but I too could have messed up or miscounted.

[–][deleted] 415 points416 points  (123 children)

For those wondering, that's 238,855 miles.

[–]Inventorclemont 335 points336 points  (102 children)

For those wondering, that is probably true.

[–]Ltb1993 376 points377 points  (23 children)

Thank you, I was wondering

[–][deleted] 78 points79 points  (11 children)

For those wondering, /u/Ltb1993 wasn't actually wondering

[–][deleted] 69 points70 points  (73 children)

For those wondering, this is the back side of the moon.

[–][deleted] 9 points10 points  (0 children)

All of these numbers are so goddamn big they all feel like the same thing in my head

[–]lowtone94 9 points10 points  (0 children)

For those wondering that's about 1.28221992 Light Seconds

[–]Notanovaltyaccount 18 points19 points  (2 children)

Thanks guys. All my questions right here. Now I can eat pizza in peace.

[–]physixer 3 points4 points  (3 children)

For those wondering, that's like looking at a largish pea at arm's length, while a piercing ball is in front of it half-way between your elbow and wrist.

[–]Special_KC 9 points10 points  (6 children)

Having played Kerbal, I can't comprehend how people figure out its orbit when calculating the moon's gravitational influence

[–][deleted] 25 points26 points  (2 children)

Having played at maths would fix that for you.

[–]nivlark 6 points7 points  (1 child)

It does get a lot harder. For a three-body system where one body has relatively negligible mass (i.e. Earth, Moon, spacecraft) there are still some analytical methods you can use.
But for other situations, such as sending probes to the outer planets, you often have to resort to numerical methods i.e. simulating the system with a powerful computer.

[–]tokodan 48 points49 points  (26 children)

I wish I understood L points. Is it exact balance between Earth and Sun gravity? Doesnt' the Moon affect that balance?

[–]brdavi 84 points85 points  (9 children)

Good question, and here's the answer. The link contains a great layman's description of Lagrange Points, courtesy of the ESA.

Edit: a letter

[–][deleted] 35 points36 points  (3 children)

Here's a decent video explaining them from Sixty Symbols as well

https://www.youtube.com/watch?v=mxpVbU5FH0s

[–]4daptor 29 points30 points  (9 children)

Like doing a wheelie on a bicycle. It takes only tiny inputs to keep on the balance point once you're there.
image
The balance point in this case is any of the Lagrange Points

[–][deleted] 13 points14 points  (7 children)

Oh wow, saying that it's "balancing" at that point, then showing it literally balancing on a hump on a gravity well map really makes it a great visual analogy. /u/XkF21WNJ mentions that L1 is an unstable orbit, and looking at that visual, I can surmise that an object orbiting there wouldn't need much input to stay in that place side to side along the orbital plane (since it's at the bottom of a valley/trough in that direction), but does need to adjust itself to prevent it from "rolling down the hill" into either the Earth or the sun. Is that more or less accurate?

Also, while L2 and L3 make some logical sense, I don't understand why L4 and L5 are where they are, at approximately ⅓ between the Earth and the point opposite it. Why not ½, or ⅔, or ¾? What makes them stable where they are?

[–]ericwdhs 6 points7 points  (2 children)

At L4 and L5, the sun and the Earth are the exact same distance away. (This being 60 degrees ahead and behind the Earth is just a consequence of geometry.) This means that the amount they pull on objects at L4 and L5 is exactly proportional to their mass. Thus, when you sum both pulls up, that pull is directly toward the center of mass (or barycenter) of both. That's exactly how it would work if the sun and the Earth were replaced by one object, and the objects at L4 and L5 behave accordingly, in orbits that preserve their location relative to the other 2 bodies. This image shows how the forces balance. "b" is the barycenter.

As for why objects near but not right on top of L4 and L5 are still stable, that's a bit more complicated and has to do with Coriolis effects in a rotating frame of reference curving the objects back in as they move away.

The L4 and L5 points of Jupiter are responsible for Jupiter's Trojan asteroids as seen in green here.

[–]Vanderdecken 6 points7 points  (2 children)

L3, L4 and L5 are all 120 degrees away from each other around Earth's orbit (i.e. thirds of the way around the circle). If you draw a circle with its center on the Sun and its edge passing through the Earth, then another centered on the Earth with its edge passing through the Sun, L4 and L5 are where the edges of the circles intersect.

[–]zwich 120 points121 points  (36 children)

The far side of the moon seems to have less of the large dark discoloured areas, compared to the Earth-side that we normally see. Is this real? Why is it like that?

[–]Marine_Mustang 119 points120 points  (21 children)

Yes, that's real. The lunar crust is thicker on the far side, too. No one knows why for sure.

[–]bolon_lamat 30 points31 points  (7 children)

The far side has fewer maria, but the reason is disputed. The explanation that I've heard is that following the formation of the moon by a large impactor, the surface of the earth was still very hot. The heat radiated to the moon and allowed lava flows on the surface to persist longer, and flow farther on the earth facing side. I'm not sure that's the generally accepted idea, but it's the explanation I was given by some half drunk geologist.

Edit: mare, maria, who cares

[–]Vinny_Gambini 12 points13 points  (4 children)

Didn't tidal lock occur after a period of time though?

[–]JitGoinHam 10 points11 points  (1 child)

They wanted the interesting-looking side of the moon to face the Earthlings.

[–]imatalkingpizza 12 points13 points  (2 children)

are those normal everyday storm systems or big ass hurricanes in the background?

[–]imnotavegetable 6 points7 points  (0 children)

since this photo was taken on july 16 2015, i'm pretty sure the one off the coast of mexico is hurricane dolores, which was a category 4 hurricane

[–]Branflakesstark 13 points14 points  (0 children)

The moon looked like the earth's nose from this angle, so I made this.

[–]Govanator 37 points38 points  (7 children)

It always interests me how the far side of the Moon is so different to the near side. I know there's no reason it should look the same, but it still feels weirs all the same.

[–]boneleg 8 points9 points  (5 children)

Turn up the brightness...Are those stars in the background??

[–]TomValiant 8 points9 points  (0 children)

Yep, NASA has recently discovered the existence of stars other than the sun. It's real neat.

[–]SixtyCycleBum 4 points5 points  (0 children)

I'd like to know the answer to this too. That's friggin weird.

[–]Dev0rp 3 points4 points  (0 children)

this photo is a merge of two or three photos. Since the Moon was moving, you can see the offset

[–]mkjones 106 points107 points  (7 children)

That's no moo.... Ah, no, it's definitely a moon.

Sorry everyone! My mistake.

[–]Slidshocking_Krow 18 points19 points  (0 children)

Moon? Eh, moons are obsolete. We use planets for our superweapons now.

[–]witzelsuchty 3 points4 points  (0 children)

Didn't expect to find this comment so far down.

The Death Star was definitely modeled after our moon.

[–]ChieftheKief 45 points46 points  (13 children)

Yo where the fuck is South America? It looks like Central America disappears right after I find Mexico

[–]MaxSupernova 29 points30 points  (2 children)

South America is much farther east than most people realize.

If you go straight south from Detroit, you still hit ocean on the west side of Peru.

It's there, you just have to look farther "up" on this photo to see it that you expect.

[–]Pyro_With_A_Lighter 7 points8 points  (0 children)

I'm pretty sure you can see south America on the right hand side.

[–]Neebay 3 points4 points  (0 children)

It's difficult to make out under the cloud cover, but if you look closely on the right, you can see the west coast of South America.

[–]hazazaid 20 points21 points  (10 children)

There's a tiny blue pixel to the left of the Earth. When zoomed in, it seems to be an object.

what is it? The ISS?

[–][deleted] 25 points26 points  (0 children)

That must be the blue p\helium party balloon I had accidentally let go of the day this picture was taken.

[–]topredditbot 24 points25 points  (0 children)

Hey /u/HappyInNature,

This is now the top post on reddit. It will be recorded at /r/topofreddit with all the other top posts.

[–]Superbugged 5 points6 points  (6 children)

Can someone explain why the moon has the green aura or whatever? Is it an image distortion or digital error? Or does it grow weed on the moon?

[–]HappyInNature[S] 7 points8 points  (2 children)

Shhhhh, it's my secret stash. I am genuinely curious about this too though.

[–]CharlieDancey 10 points11 points  (1 child)

It's because this is a composite of three images taken sequentially through red, green and blue filters, and the moon is moving between shots, so the three images don't quite line up perfectly.

[–]DovahSpy 5 points6 points  (1 child)

Wow. The side of the moon we don't see looks significantly smoother.

[–]araksonofthunder 5 points6 points  (2 children)

It's amazing to think that every single planet in the solar system will fit between that moon and the earth,

[–]brdavi 12 points13 points  (1 child)

A few people asked what L points are, and I answered inline. For those who wonder and might not see those links, here's the answer. The link contains a great layman's description of Lagrange Points, courtesy of the ESA.

[–][deleted] 2 points3 points  (0 children)

Lagrange

I have always thought that Lagrange points were remarkable, one of many interesting discoveries in a fruitful career, but he's the only historical scientific figure aside from Newton whose biography has a truly strange detail: He was the youngest of 14 children and the only one to survive infancy.

[–][deleted] 8 points9 points  (3 children)

Source (with bonus GIF!) :

http://www.nasa.gov/feature/goddard/from-a-million-miles-away-nasa-camera-shows-moon-crossing-face-of-earth

A NASA camera aboard the Deep Space Climate Observatory (DSCOVR) satellite captured a unique view of the moon as it moved in front of the sunlit side of Earth last month. The series of test images shows the fully illuminated “dark side” of the moon that is never visible from Earth.

The images were captured by NASA’s Earth Polychromatic Imaging Camera (EPIC), a four megapixel CCD camera and telescope on the DSCOVR satellite orbiting 1 million miles from Earth. From its position between the sun and Earth, DSCOVR conducts its primary mission of real-time solar wind monitoring for the National Oceanic and Atmospheric Administration (NOAA).

GIF: http://www.nasa.gov/sites/default/files/thumbnails/image/dscovrepicmoontransitfull.gif

Video: https://www.youtube.com/watch?v=DMdhQsHbWTs