Tsukiyumi Note #052 Moon Returner | "Orion" Returns from its Journey to the Moon

You can download the teaching material PDF for free at the end of this article. Please feel free to use it for home study.

Why can't we see the far side of the moon from Earth?
Why is there a "6 minutes of terror" when communication is lost as a spacecraft returns to Earth?
What measures are taken to communicate with a spacecraft on the other side of the Earth?

Mom: "While I was making this teaching material, the song 'Kagome Kagome' was on repeat in my head the whole time. The moon going around the Earth, 'the bird in the cage...' you know. And the Earth, surrounded by the moon and unable to move, finally breaks out of the moon's enclosure. Isn't it crazy that the Earth gets behind the moon while the song is asking, 'Who is behind you?'!!"
Tsuki: "Uh, is 'Kagome Kagome' a tomato juice???"
Mom: "Huh? You're starting from there? I thought I was saying something super interesting... It ruins it if I have to explain from scratch that it's a traditional children's song. Try to keep up with me without me having to spell it out."
Tsuki: "The Showa era is too much for me..."
Mom: "(No, no, it's the Edo era... I think, I don't know)"

In April 2026, the crewed spacecraft "Orion" returned from its journey to the moon as part of the international "Artemis" project led by NASA and others. For the first time in half a century since the Apollo program, astronauts have seen the "far side of the moon" in person.
Why can't we see the far side of the moon from Earth? The moon in the night sky always shows the same pattern to Earth. The moon rotates on its axis just like Earth, but because the time it takes to orbit the Earth is exactly the same as the time it takes to rotate once—about 27.3 days—we always see the same side from Earth. This is called "tidal locking." The far side has few flat areas and is covered with countless craters.
When a spacecraft returns to Earth's atmosphere at high speed, a phenomenon called "adiabatic compression" occurs as it violently crushes the air in front of it, causing the area around the craft to reach an extreme temperature of 2,700 degrees Celsius. This turns the air into a charged state called "plasma," which reflects or absorbs radio waves, making it impossible to communicate with the ground for about 6 minutes.
Furthermore, because the Earth rotates, if there were only one antenna, the moon would be hidden behind the Earth, making communication impossible. Therefore, antennas are placed in three countries: the United States, Spain, and Australia. These are separated by about 120 degrees in longitude, so even as the Earth rotates, the three locations catch the moon like a relay race, ensuring constant communication.
In Australia, in the Southern Hemisphere, development is also underway for the "Loo-ver," a kangaroo-like lunar rover that won't slip even in low gravity. The exploration of deep space is made possible by understanding Earth's physical laws and through the cooperation of countries around the world.

Let's try it
● Work 1: Experience "tidal locking" using your own body
Verify the mystery of why the moon always faces the same side using your own body. Place a chair (Earth) in the middle of the room, and you become the moon. Try walking sideways in a circle while facing the chair. When you return to your original position, your body has naturally rotated once (rotation). You can experience the mechanical principle of how rotating while orbiting allows you to keep facing the same side.
● Work 2: Create the heat of the "6 minutes of terror" with a bicycle pump
The extreme heat when a spacecraft enters the atmosphere is caused by "adiabatic compression" of crushing the air, not by friction with the air. Prepare a hand-operated bicycle pump and firmly block the end of the hose with your finger so that no air leaks out. Try pushing the handle down quickly a few times. Feel the cylinder get hot with your hand, and you can experience the law that kinetic energy turns into heat.
● Work 3: "Quiet observation" to feel physical laws
Take time for "kaizute," a practice valued by physicist Torahiko Terada, which means stopping work and standing still. Sit in a chair or stand and close your eyes, and stop moving completely for one minute. Focus only on the physical phenomena touching your body, such as the temperature felt on your skin, the sounds reaching your ears, and the gravity on the soles of your feet. After opening your eyes, try to put into words the law you felt most strongly.

The above is an excerpt from the teaching materials I am creating for home study with my son (Tsuki).
[Teaching Material Content] Moon Returner

The mechanism of "tidal locking" where the moon's rotation and revolution are synchronized
The true nature of adiabatic compression and the plasma sheath that occurs during atmospheric reentry
The 120-degree placement of the deep space communication network considering Earth's rotation
Center of gravity design for the lunar rover "Loo-ver" under low gravity
The importance of a scientist's observational eye and curiosity through the writings of Torahiko Terada
Records of the crewed mission that directly observed the far side of the moon for the first time in half a century since the Apollo program
Essay (Composition): "Technology and Cooperation Across Space"
Debate: "Should space development be prioritized over solving Earth's problems?"

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