> "I'm sure they neither knew nor cared" They did, actually -- Pytheas had observed that true North was "devoid of stars" way back in 320 BC. Polaris didn't b

> "I'm sure they neither knew nor cared" They did, actually -- Pytheas had observed that true North was "devoid of stars" way back in 320 BC. Polaris didn't begin to be recognized as the "North Star" until much later (10th century according to wikipedia), because it wasn't particularly close. Navigators learned how to find where north was from several stars; it's only been the last several centuries that Polaris has been close enough to North as to be treated as the default for navigation. They also knew about precession (credited to Hipparchus in the 2nd century BC, but possibly an older discovery.) So they knew that north wouldn't be in exactly the same place centuries later. Differences of a few degrees were a pretty big deal to people who both navigated by, and gave religious significance to, the stars. I don't know the details of early Sumerian astronomical navigation schemes. From what I understand, our knowledge of their astronomy comes from Babylonian sources a couple thousand years later, and is not particularly detailed or reliable.