Why is the greenhouse effect only one way?

Question

So what I’m reading is that these gas absorb the light from the sun and keeps it trapped on the earth.

What I don’t get is how is it letting the light and heat in from the sun in, but not the light and heat reflected from the Earth out? If it’s a barrier, shouldn’t it block both ways? If it’s not a barrier, how is it trapping the heat?

In: 950

Answer 1

The difference is in the wavelength. CO2 and other greenhouse gasses block infrared light, ie heat, but not so much visible light. Unlike Sun, Earth doesn’t radiate visible light, only infrared light.