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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!
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