PV Gap

William Said:

why dont greenhouse gases absorb solar energy as it comes from the sun rather than after?

We Answered:

So far, no one has provided the correct explaination, makes you wonder how much the so called experts here really know. As with all things, it is not as simple as you might think.

The sun emits energy in many ways, but much of what reaches the earth is electromagnetic radiation in the visible spectrum, that is, light. The Earth's atmosphere, including green house gases such as CO2, H2O and NO2, is essentially transparent to visible light and thus, it passes through the atmosphere with little loss and reaches the planetary surface. At the surface, some of the visible light is absorbed, if it wasn't, the Earth would look like a shiney mirror ball, the enegy in this absorbed light is converted to heat (i.e. when the light is absorbed, the molecules of the surface begin to move more rapidly. Some of this energy is then reradiated from the surface as electromagnetic radiation in the infared spectrum (you can't see this, but you can feel it as heat radiating from a hot surface). So called green house gases are not transparent to infared radiation, and thus absorb it, much as the surface absorbs visible light. This heats these gases up.