Why doesn't the moon fall down if it's just a big rock?

[rootone]

Is there an easy way to explain this to a 3 year old?

 

[fresh_42]

Is there an easy way to explain this to a 3 year old?

Do you also play with them by holding their hands and let them fly in circles? If so, then you have explained the centrifugal force. Together with the weight of the rock it becomes an equilibrium, same as your hands balance the centrifugal force by a pull. That's what I would try. Alternatively use one of this artificial funnels where you can roll a coin which in the end drops into the shaft in the middle: the coin would roll endlessly like the moon if there wasn't friction.

 

[kuruman]

Tie a ball at the end of a string and ask the 3 year old to swirl it in a circle. Ask him/her to note that although the rope is pulling on the ball, the ball isn't moving towards the hand but goes around in a circle. In a leap of faith say that the Earth plays the role of the hand, the Moon plays the role of the ball and the invisible attractive force of gravity plays the role of the string.

 

[fresh_42]

Of course you can also tell right away the truth: The moon actually falls towards the earth, but he is so fast that he constantly miss it. I suggest a shopping cart and a ball to demonstrate the effect: place him / her in the cart, hand out the ball and let him / her throw the ball towards a certain object on a shelf while you are rushing the cart through the aisle.

 

[kuruman]

Of course you can also tell right away the truth: The moon actually falls towards the earth, but he is so fast that he constantly miss it. I suggest a shopping cart and a ball to demonstrate the effect: place him / her in the cart, hand out the ball and let him / her throw the ball towards a certain object on a shelf while you are rushing the cart through the aisle.

If I were the 3 year old in the cart, I would see the ball (Moon) fly through the air and eventually hit the floor (Earth) which is exactly what is not supposed to happen. I don't think a 3 year old is developed enough to appreciate the subtlety of the effect that you propose.

 

[Orodruin]

If I were the 3 year old in the cart, I would see the ball (Moon) fly through the air and eventually hit the floor (Earth) which is exactly what is not supposed to happen. I don't think a 3 year old is developed enough to appreciate the subtlety of the effect that you propose.

Some 3 year olds are also surprisingly apt at these things and may unconsciously correct for relative motion.

 

[rootone]

Thanks for you advice people.
I tried to explain that the Moon really did want to fall down, but the Earth was moving away as fast as the Moon can fall.
The young one said, ah I get it, the moon is in space and 'space is bendy'.
This kinda of puts me into a state of shock.
The mother of the child seeing this suffering going on, says 'no he didn't say bendy'
He said space is windy.

 

[mfb]

but the Earth was moving away as fast as the Moon can fall.

That is wrong and I think it is misleading at the same time.

 

[fbs7]

Hmm... I'd revolve a teddy bear on a string, and say "see, the force of the string is making the bear fly in a circle!", then say "there's an invisible string attached to the moon called gravity, and that also makes the moon fly in a big circle!".

 

[kuruman]

Hmm... I'd revolve a teddy bear on a string, and say "see, the force of the string is making the bear fly in a circle!", then say "there's an invisible string attached to the moon called gravity, and that also makes the moon fly in a big circle!".

In post #3 I suggested using a ball at the end of a string. Does a teddy bear work better?