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At 12:23 07/09/2006, I wrote:

>If the car had not been there, a similar equation could have been 
>applied to the heat 'shining' onto the ground. The ground is likely 
>to store (again, temporarily) even more heat than the car, but has 
>no door to open, letting out that spectacular rush of warm air which 
>confused your friend.

Come to think of it, the same area of bare ground is likely store 
less heat than the car. Hot ground and hot car-seats both radiate 
some heat back towards the sky, but the longer wavelength of this 
radiation is less able to pass outwards through the car window-glass. 
The energy equation has to balance, so more heat builds up inside the car.

Comparing a parked car with a similarly sized patch of ground seems a 
useful way to consider this 'greenhouse effect'. The difference 
between the car and our planet being that a planet can ONLY lose heat 
through its atmospheric window, so it isn't likely to cool down as 
much as the car at night...


[log in to unmask] * http://www.interactives.co.uk
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Give people facts and you feed their minds for an hour.
Awaken curiosity and they feed their own minds for a lifetime.
*
Ian Russell 

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