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This morning I looked outside at my car and windows were covered in ice. The temperature this morning was -7F. A couple of hours later now the temperature is 0F, yet everything on the car is shiny and clear.

What happened to the ice? It just disappeared.

Edit: The car was in the sun.

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    $\begingroup$ Was your car in the sun? $\endgroup$
    – Jon Custer
    Jan 31 at 17:40
  • $\begingroup$ > Add details and clarify the problem you’re solving. This will help others answer the question. I'm not sure what other details this requires? $\endgroup$ Feb 3 at 17:09
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    $\begingroup$ Ice does sublimate (that is, go to the gas phase without melting in between, and faster than one might expect): <phys.org/news/…>. $\endgroup$ Feb 3 at 17:20
  • $\begingroup$ Btw: I am not sure why this question was closed – it is conceptual (how can ice melt, or otherwise disappear in temperatures below freezing) – which has the interesting possibility of the ice sublimating – next to the mundane one, that the sun heated the car above the melting point. $\endgroup$ Feb 3 at 20:28

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If the car was in the sun, the paint, glass and metal of the car will absorb energy from the sunlight and warm up slightly. the frost will then melt, but only on the sunny side of the car.

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  • $\begingroup$ To further test this I brought a laser thermometer outside. It's 22F outside and half my car has been in the sun for a while. Suprisingly to me, the sun-side of the car's body is 65F! The shaded side is 16F. I guess the car body absorbs way more energy than I expected $\endgroup$ Feb 5 at 16:23
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In this time lapse of the sun melting frost off of a car, sunshine appears to sublimate the frost it strikes, but once enough of the window is clear, frost still in the shade starts to melt. This is presumably because the car now acts as a greenhouse with the sun heating the car's interior which then heats up all the windows from within.

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  • $\begingroup$ This was a very cool video demonstrating the greenhouse effect in the case $\endgroup$ Feb 5 at 16:16
  • $\begingroup$ "in the car"* (cannot edit comment above anymore) $\endgroup$ Feb 5 at 16:24

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