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 sunlight comes in and warms everything as things absorb the light. This is sunlight in every colour of the rainbow.

But warm things put out light in mostly infra red. Just that one colour.
Glass of a greenhouse let’s in the whole rainbow but blocks infrared getting out. CO2 does the same.thing.