Internet version [Naruhodo no Mori] Vol.26

by Yumiko Mori

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Vol. 26     February 15th, 1997

Learning how big the space is (No.2)

Home science experiments for mothers of elementary school children

Materials

• Sesame seeds....several
• A balloon
• A marker pen

Naoko: "Hello!"
Mom: "Hello, Naoko! Would you like to join us?"
Naoko is Tae's best friend.
Mom: "We were just talking about the solar system. Planets like the Earth or the Venus do not shine by themselves. Only the Sun is shining. But most of stars you see at night are shining. "
Naoko: "Really? That's interesting."

Suddenly Mom puts a tiny sesame seed on the desk.
Naoko: "What's going to happen?"
Mom: "Well, let us assume this seed is the size of the whole solar system."
Tae and Naoko: "What? Just this tiny seed?"
Mom: "You are going to guess where the nearest shining star would be in this scale."
Mom hands Tae and Naoko one sesame seed each.
Naoko: "It must be very very far. Don't we count such distances by light year? Right? How about around here."
Tae: "I put mine here."

If 10 billion km is equivalent to 1 mm
The size of the whole solar system	~6000 million km	~0.6 mm
1 light year	~1,000 billion km	~1m
The size of the whole Galaxy	~100,000  light years	~100 km
The distance to the farthest galaxy	~13500 million light years	~13.5 million km

Mom is having a fun. She can not help smiling.
Mom: "The right answer is..."
Mom picks up a seed and walks to the next room.
Tae: "You cheated! That's not on the top of the desk."
Mom: "If the whole solar system is the size of a sesame seed, one light year would be 1 meter long. Since the nearest shining star from the Sun is 4 light years away, it would be 4 meters away in this scale."

Mom: "Then where is the farthest star?"
Naoko: "It must be very very very far."
Mom: "You guessed right! 13,500 million light years away! Even in this sesame seed scale, it would be 30 times a distance to the Moon."
Naoko: "Is it a known fact?"
Mom: "The farthest one is actually a galaxy, a group of many stars."
Mom: "Actually there are many galaxies in the whole space. At least 10 galaxies are as far as this farthest galaxy."
Naoko: "Incredible! Now the human knows a lot about the space."
Mom: "No! No! There are much more to be studied in space science."

Mom: "I can talk to you about something even more amazing. I said the space is huge in size, but when it was born, it might have been smaller than this sesame seed."
Tae: "I can't believe it! How did scientists find this?"
Mom: "From observations, scientists have discovered galaxies keep moving apart rapidly."
Then Mom blows up a balloon. She drew dots on the balloon with a marker.
Mom: "These dots are supposed to be galaxies, OK?"
Mom blows up even more.
Mom: "Watch those dots are moving away from each other on the surface of the balloon. By this way scientists have found the space is expanding."
Then she released air from the balloon. The balloon shrank immediately.
Mom: "Look! Before expanding, the space was very small like this balloon now. Shall I continue to talk about the birth of the space, so called the Big Bang."
Tae: "Your talk is getting very long. You can talk to us another time. Now it's time to play. Bye, Mom!"

  Every time I read this particular 'space' book, I get so impressed and excited. One reason is that it is often so difficult to understand the concepts that I cannot memorize them. Another reason is perhaps because of lack of my imagination and memory capacity. On the other hand I can enjoy reading this book repeatedly without getting bored. The space is so vast and there are so much unknown. We will enjoy learning about the space as more discovery are found.

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