I just finished my ten thousandth watch if Moana with my son, and I do not understand how you can travel by holding your hand up to the starry sky. It would make sense if the stars were stationary relative to your position, but they’re not. A star you measure at 10pm is in a completely different position by 2am. I understand the Disney version is an oversimplification, but how does the real thing work?
In: Earth Science
>A star you measure at 10pm is in a completely different position by 2am.
Except for one. Since the stars *turn* in a circle there’s one spot in the sky that doesn’t move— the center of the circle. In the northern hemisphere, just by coincidence, there’s a star almost exactly at that spot. A fairly bright one, too, called Polaris, at the end of the handle of the Little Dipper (the tail of Ursa Minor).
If you can see and identify Polaris you know that that direction is north, which lets you keep the boat pointing in the right direction. But also, if you can measure how far it is above the horizon, *you’re that far north from the equator,* in terms of degrees latitude.
If you’re in the southern hemisphere, it’s harder. There’s still a stationary spot in the night sky, but there’s no star right on top of it. You can do the same trick by finding the spot where an imaginary star *would* be (by recognizing the stars nearby), but it’s harder to get good measurements.
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