what do you call the night sky?

Because during the day it's called the "sky", at night the sky isn't there anymore and all you can see is the stars and space, but the thing is the sky is still there. And the "night sky"... that's two words. What's one word? I've never heard of it.

Solution 1:

Since Middle English borrowed an old Norse word for cloud, it's just been

sky

The atmosphere and outer space as seen from the earth; the place in which clouds, stars, and the sun and moon appear, esp. as regarded as a great canopy or vault

If that's confusing to you, just think to yourself "Where's the moon?" "It's in the ____." It should come pretty naturally to say "sky" even though when you think about the sky you usually picture the daytime version.

If you want to be poetic about it, you can call them the heavens. If you wanted to be poetic and Scottish, there's the lift, although that's going to be followed by incomprehension.

If you want to be misinformed about it, you call it the firmament, based on a Latin translation of a Greek translation of a Syriac misunderstanding of a Hebrew word for expanse. The image is of a great firm ceiling above or around the Earth, beyond which lies the empyreal realm of elemental fire.