Gravity at Work - "Space Force" - a Toy

"Space Force" was a toy we bought 4 or 5 years ago when we visited Houston Space Center and Science Museum. We placed it on top of the bookshelf along with a model of space station as decoration to our study. From time to time I did wonder that how it could be played - but we lost the box and instruction, so it has stayed on top of the bookshelf all these years.


A weekend several weeks ago, Nick was asked to stay away from computer for an hour to rest his eyes. He wandered around the house, nothing really interested him that morning, so he came back to the study (where the computer is), then he saw the pendulum like toy on top of the bookshelf - he asked me to take it down for him.

How to play

He took the toy to playroom and tried to figure out how to play it. He was quiet and stayed there for an hour or so. Then he declared to me that he knew how to play it.

"You place it on the floor, then place the steel ball at the pinned side of the wires. You push the wires apart slowly and try to make the ball roll as far as possible" . "You see, there are numbers on it:

Mercury -250
Earth 250
Mars 500
Jupiter 1000
Saturn 2000
Pluto 5000

You score points when the ball drop into a hole."



Trying to make the ball roll to the Pluto - the furthest planet and highest score hole, he played it again and again. He was fascinated by it. When he finally figured it out, he asked to have a game with his Mom and easily beat her.

After lunch, he kept playing on. I was curious now - I sat by him, observing him play.

A game of gravity and inertia

The top, or the narrow side of the toy, is lower than the wider side or bottom of the toy, when it is placed horizontally on the floor or a table. When the two wires touching each other at the bottom side the ball will stay at top side.

To make the ball roll to the direction of bottom, one has to push the wires apart - make the ball to fall in between wires, so gravity will make the ball roll and gain speed. If the wires are left apart, eventually the gap (which changes with distance) between them is too large the ball will fall.

The trick: as the ball gaining speed, pushing the wires close, now the ball has to go from low to high, the ball is moving against gravity! No worry, inertia can keep the ball moving forward for a second or so if the speed is high enough. Just as the ball's speed decreases to zero, push the wire open - the gravity will be a favorable force again - pushing the ball toward Pluto!

The competitions

Nick played a few times by himself, and boasted to me that he beat his Mom easily. "Let's play the game against each other" He challenged me. "OK", I said, "But I need to practice a few times". He agreed.

We had a pencil and a piece of paper ready before we start the game. We would each play 10 times, and the one has higher total score win. Nick played first, he got to Pluto once, but he also dropped the ball at Mercury once - negative points. I reached Pluto twice and the rest were all further away from earth. I won the first round.

Nick did not whine, and was in a good mood. After listening to my explanation of the mechanics of the game - gravity, inertia and etc, he asked to have a rematch.

Playing the game requires more than understanding of the mechanics, when one knows the mechanics - by knowledge or by trial and error, it is more of an art - how fast or slow to push the wires apart, when to push the wires to each other, and when to push them apart again. The second time, Nick reached the Pluto 3 times, I got there only once. Nick won the rematch and was very pleased.

This is an educational and fun toy.