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

To add to others good answers, we *can* do the opposite with materials designed to emit wavelengths transparent to our atmosphere. [Here is a cool video on making it](https://youtu.be/N3bJnKmeNJY)