[Squeakland] More thoughts - Re: Demoing Etoys to kids

[stéphane ducasse]

Ok thanks I missed the distance from the eye :)

Stef

On 12 août 07, at 21:42, Alan Kay wrote:

> Hi Stephane --
>
> At 12:11 PM 8/12/2007, stéphane ducasse wrote:
>> Hi alan
>>
>> I always liked the way ancient measured pyramid using the shadow of a
>> know piece of wood and use Thales theorem.
>> At least it was a really practical example, I used to teach Thales
>> beauty.
>
> Yes, and it is even simpler for the children to think just in terms  
> of similar triangles.
>
>
>>> For example, if we occlude a quarter with a dime and measure this
>>> carefully, we see that the distance in diameters has to be the same.
>>> <dimeQuarter.png>
>>
>> Now I do not understand the "distance in diameters"
>
> Check the picture. If it is 9 dimes from the eye to the dime, it  
> will be 9 quarters from the eye to the quarter. If it is 110  
> quarters from the eye to the quarter that occludes the moon, the  
> moon is 110 moon diameters from earth.
>
>> Which
>>>
>>> And if we then occlude the moon with a coin (as Aristarchos of
>>> Samos indeed did!) we will find that it takes about 110 coin
>>> diameters, and this means that the moon is 110 moon diameters away
>>> from us!
>>
>> How do we get 110?
>
> You measure the number of coin diameters from the eye to the  
> location of the coin that occludes the moon.
>
> Cheers,
>
> Alan
>
>
>>>  Children love this (too bad adults don't, or they would know about
>>> this and teach it to children).
>>
>> Some do :)
>>
>> Stef
>>
>
>