system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does moon in daylight looks transparent?
gpt
1. We imagine the daylight sky is blue and everything is in front of it.

2. But actually, the sky is just the atmosphere, and the moon is behind the atmosphere.

3. So the sky is *in front* of the moon.

4. It's the sky that's transparent.