For example, what is the reason why greenhouse gases reflect heat from the Earth back to Earth, but not heat from the Sun back to the space?
From what I understand, it has something to do with radiation and emitted waves, but what exactly makes the difference?
In: Planetary Science
Radiation that comes from the sun is mostly visible light. Visible light passes through the atmosphere mostly unimpeded.
If this visible light hits something like a mirror or a very reflective surface (snow, ice, etc.), it simply gets reflected into space, and the atmosphere also doesn’t impede that light on the way back up.
However, a lot of visible light is not reflected. It is absorbed by the surface, which warms it. Over time, any warm surface emits its heat back into space, thats why it’s getting colder during the night … only Earths emission does not happen in the form of visible light (that would require a surface that is thousands of degrees hot), but rather in infrared light. It is this infrared light that greenhouse gasses are so good at absorbing.
And thats why the atmosphere absorbs radiation energy mostly only in one direction.
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