system
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human
The brightness of the actual dark side of the moon?

With the extremely thin atmosphere on Earth's moon, and a complete absence of cloud cover, foliage, etc., what sort of luminosity would the various stars and Milky Way provide on the moon's night?  Meaning - if both Earth and the Sun were 'behind' you as you were standing on the moon, would it truly be pitch black, or could once expect a level of light to at least, say, see enough to not walk into a boulder?
gpt
Not much darker than a "dark sky" spot on Earth.

The Earth's atmosphere mostly reflects back urban light. But go out in the desert, or out at sea, at least 100 km away from any city and town - it's a pretty dark place. Luna wouldn't be very different - a bit darker maybe, but not much.

Most people have lived in cities their entire lives and have no idea how dark a moonless (and Venus-less) night can be at a dark sky site.

Dark adaptation is very important. When at a very dark site, it takes something like 20 or 30 minutes for the eyes to fully adapt to darkness. Even a short glance at a light annihilates this adaptation.

> could once expect a level of light to at least, say, see enough to not walk into a boulder?

You could avoid big boulders, but there will be plenty of rocks that will twist your ankle - as many astronomers fumbling in the dark around telescopes will attest.

Human eyes in low light have very, very poor resolution. But boulders should be big enough to distinguish, for a dark-adapted pair of eyes. Fist-sized rocks, not so much.