I can honestly say I’ve never thought about this. But today’s video from the YouTube channel MinutePhysics explains why the sky is dark at night. You might say reflexively, as I did, because the sun isn’t up. But that’s not the answer.
If we didn’t have an atmosphere to scatter the sun’s rays, the sky would be dark during the day too. And isn’t it true that there are billions of stars out there, in every direction?
The video makes a fascinating claim. If the universe was infinite and never changing, even when the sun sets the sky would be bright all the time. Watch to learn why.