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The dark side of the moon. Mysterious.

Intriguing. Why does it have so much lore associated with it? Maybe because it took three spacecrafts visiting before we had any idea what it looked like!

So here’s how we finally got pictures of  the dark side of the moon for the first time and what it took to get  those images back to Earth. In October 1959, we got our first  pictures of the dark side of the moon thanks to the former Soviet  Union’s Luna-3 spacecraft. It was the third spacecraft to go to the moon.

So two missions were complete before we even tried to snap some pictures of its  far side, and it wasn’t an easy feat. Luna-3 took pictures just like how we  would take them on Earth back then: with a camera and film processing equipment. But the impressive part is  that the spacecraft then sent those pictures to Earth using electrons.

First, a camera was mounted in the  probe to take the original photos. The film had to be temperature-  and radiation-resistant because of the unwelcoming environment of space. But this film, just like film on Earth,  had to be developed, fixed, and dried.

And all of that processing happened automatically within the probe while it was still in space. Then, six antennae mounted on the outside of the probe transmitted the images to Earth. They were similar to the  antennae on old household TVs.

A cathode ray, which is made of streams  of electrons inside a vacuum tube, produced a bright light that  shone through the developed film and onto a super-sensitive detector  called a photoelectric multiplier. This light comes from the  electrons crashing into gas inside the cathode ray tube or a  special material coating the ends. When that happens, the coating glows.

We can see it as light  because the coating converts electrical energy into light energy. It’s like when you eat and take the energy  from your food to energize yourself. In Luna-3, the cathode ray  scanned the whole image.

Then, the intensity of that  light was converted into an electric signal and scanned  with a 1,000 line resolution. This is similar to how televisions used to work; those same old ones with the antennae. Then it passed the electric  signals through a modifier and to a magnetic recording device on Earth.   When Luna-3 scanned the images,  it produced light gradients to represent what was photographed,  and it did this along slow, even, straight lines like a printer.

That’s why the images look striped. Then, back on Earth, a light-sensitive film was put in front of a screen to capture the image. But those images were far from a full story.

We got a glimpse at just 70%  of the dark side of the moon. And we didn’t get 100% for a few reasons. First, Luna-3 was on a  trajectory to orbit the moon and take images while it traveled.

It had photoelectric cells that used  sunlight to align the probe to face the moon. But there were no rockets on the spacecraft, so course correction was not an option. And it couldn’t pause its  orbit to get a better angle.

So even if everything went according to plan, it was never supposed to image  100% of the dark side of the moon. Another reason we didn’t get a complete  idea of what it looked like is that. Luna-3 took 29 pictures, but only 17  full images were transmitted to Earth.

A cathode ray isn’t perfect. It’s not super detailed in bright  environments and can only use a limited number of grey shades to make an image. It’s pretty impressive that  we got any images at all.

Now, the images could be  sent to Earth at any point, but the signal was stronger when  the probe was closer to Earth. Today, scientists think the partial  images that were received on Earth were a result of Luna-3 being so far away. While we might not have  gotten a complete picture of 100% of the dark side of the moon, those first images told us that the far side  of the moon is full of craters of all sizes.

This isn’t how the near side  of the moon looks at all. So it was an important step in  learning more about our moon’s history. But the moon isn’t the only mystery here.

Four days after the last photo was sent,. Luna-3 disconnected its  communications and never came home. Its fate is still unknown, but there are  a few ideas about what happened to it.

It might have burned up in an attempt  to re-enter Earth’s atmosphere. Or maybe it stayed in orbit and flew in  circles around Earth for another two years. So Luna-3 joins the list  of moon-related mysteries.

Since the Luna-3 mission, humanity has  revisited the dark side of the moon several times and brought  home higher resolution images. So today, that dark side of the  moon is far less mysterious. Luna-3 may have mysteriously vanished, but you can bring it home on this awesome pin!

Check out the link in the description  to snag this Pin of the Month inspired by Luna-3’s mission  to the dark side of the moon. It’s available for preorder  until the end of the month, when ordering will close and  we’ll start shipping them out! And remember to keep your eyes  peeled for the next pin in November.

Thanks for watching this episode of SciShow Space! [♪ OUTRO].