Somewhat belated open thread for this month! (Oops). Please stick to climate related topics, and remain respectful.
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15 Responses to "Unforced Variations: Apr 2026"
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On April 11, in the March UV, Ron R mentioned the “picture perfect” Artemis II flight. I have a science question about pictures from that picture perfect flight. Can you imagine? Actual science!
My question is what is going on with these 2 photos of the earth. The first one says it is a photo of the backlit dark side of the earth. What is doing the backlighting – the moon? FYI, You may need to turn up your screen brightness to see details.
https://www.nasa.gov/image-detail/amf-art002e000193/
The second photo shows the exact same image, taken from the exact same location. Every land mass, star, and cloud is in the exact same location except the earth isn’t dark!
https://www.nasa.gov/image-detail/amf-art002e000192/
How can that be? Which image is fake (or altered) or are they both fake (or altered)? They used a monster flash to light up the earth in the 2nd image?
:)
Camera settings control what the camera sees– variables like exposure, aperture, ISO, and these days in camera processing
Image processing programs provide tools to bring out information captured by the camera that you don’t necessarily see, for example like what you did when brightening the screen.
In astrophotography you can also take multiple images of a single area of sky, stack and combine them to capture more light in a single image. That’s probably not what happened here though.
KIA,
Go with what Ray said.
Mr. KIA, The illumination is in fact “moonshine”. The difference is the exposure time. More time means more photons means lighter pixels.
James Webb Space Telescope has to use integration times up to about 20 minutes for some of the fainter objects it images. At that rate, you can start to see hits by cosmic ray particles, so they also have techniques for rejecting the charge due to cosmic rays (which tends to come in big chunks all at once) and still get a good image.
With astrophotography, bright objects need short exposures or the pixels get filled and the image whites out. Dim objects require long exposures.
KIA, hmm, I don’t understand your question. Seems pretty clear to me. You’re looking at the dark or night side. What is the light source on the other side? It clearly indicates it’s the sun, “as the Earth eclipses the Sun”. It also says in the dark picture, “Artemis II Captures Dark Side of the Earth”
They simply brightened the picture by turning up the exposure probably because they’re highlighting the auroras that you can barely see in the darker picture. It even mentions them in the brighter picture. Also notice that in the brighter picture the rim of the sun on the edge is brighter in comparison and you can see the halo now.
No, you didn’t discover a conspiracy.
Hi Ron,
I think Ray said it best, which I interpret this way: In order to enhance the photo, there had to be something to enhance. The back side of the earth was faintly lit by sunlight reflected off the moon. I don’t think the other light sources you mention would be sufficient to cover the whole dark half of the earth so evenly.
BTW, Commander Reid Wiseman used a Nikon D5 DSLR camera to take the shot. It’s an older camera but check this out:
The 10-Year-Old Nikon D5 DSLR Really Is the Best Camera for Artemis II
https://petapixel.com/2026/04/06/the-10-year-old-nikon-d5-dslr-really-is-the-best-camera-for-artemis-ii/
The image was apparently post processed in Adobe Lightroom Classic, not super high tech.
Radge Havers, there is something to be said for older tech.
Thanks for that informative article. Photo taken at 1/4 second shutter speed, ISO 51,200. WOW! So, a relatively slow shutter combined with very fast “film” (digital image sensor) and it can essentially see in the dark. Surprising that it wasn’t super grainy given the high ISO – that’s what happened with high speed film in the old days. If you wanted high resolution (small grain) you might use ISO 25 or ISO 64 film, but no higher than ISO 100 and certainly not 51,200! Will have to investigate how ISO 100 for film compares to ISO 100 for digital sensors.
Good video on the Artemis II mission, with a little more about that photo at 5:35:
https://www.youtube.com/watch?v=4N3GJnDiqCU
Grain can be managed. The Nikon D5 has in-camera noise reduction settings. Where those are week, photo software programs worth their salt will have a denoise function.
There are a lot of approaches to fine tuning your image in post processing, particularly if you shoot in RAW format.
Oops, Ray was right that the light was coming from the moon (but visible thanks to the camera) not simply longer exposure to the sun on the other side of earth. Both images are real of course.
Always trust the physicist over the non-scientist. :)
“How Internal Waves Transport Energy Thousands of Miles Across the Ocean”
https://eos.org/research-spotlights/how-internal-waves-transport-energy-thousands-of-miles-across-the-ocean
Here is the answer:
What I don’t understand is how tides can be responsible for this massive wave motion, yet for similar subsurface wave motion that creates an El Nino, it is considered due to the wind. So, the conventional wisdom of consensus science says the roles are essentially reversed here as the tides are considered inconsequential. …. Hmmm, Aha! This is reconciled when one considers the possibility that the tides are also responsible for the wind, and this correlation becomes spurious as the mechanisms. work in phase to establish the El Nino dynamics.
F= GMm/r^2
Gravitational attraction. The earth’s crust and the oceans are deformed by the gravity of the orbiting moon.
Wrong formula. But you’re a know-it-all so you should be able to figure it out.
Tides are efffectively the first derivative of the gravity. So they scale as r^-3 with directional components (dipole field).
I think a lot depends on the wave period, which for tides is mostly 12 and 24 hours (slighly different because of the moon’s travel in it’s order). Wind is generally seconds to minutes, and drives at the surface, so you get the familiar gravity waves. These deep waves are usually internal waves -often
gravity waves trapped at the boundary between layers of different densities. The tidal forces (stresses) are a body force, which means it is distributed throughout a volume, not just a surface.
FYI:
Critical Atlantic current significantly more likely to collapse than thought
The Guardian / UK
April 15 2026
“The Atlantic meridional overturning circulation (Amoc) is a major part of the global climate system and was already known to be at its weakest for 1,600 years as a result of the climate crisis. Scientists spotted warning signs of a tipping point in 2021 and know that the Amoc has collapsed in the Earth’s past …
“The research combined real-world ocean observations with the models to determine the most reliable, and this hugely reduced the spread of uncertainty. They found an estimated slowdown of 42% to 58% in 2100, a level almost certain to end in collapse.”
https://www.theguardian.com/environment/2026/apr/15/critical-atlantic-current-significantly-more-likely-to-collapse-than-thought
https://www.science.org/doi/10.1126/sciadv.adx4298