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Why the Big Dipper rotate on North Star?

(2025-07-27 19:53:32) 下一個
Why does the Big Dipper rotate around the North Star?
ChatGPT said:THE BIG DIPPER NEVER SETS  Look up on ...Night Sky Guides: Big Dipper, North ...

The Big Dipper appears to rotate around the North Star (Polaris) due to Earth's rotation on its axis.

Here’s a breakdown of why this happens:


1. Earth Rotates

Earth spins once every 24 hours from west to east. This rotation causes the sky to appear as though it’s rotating in the opposite direction—east to west.


2. Polaris Is Almost Directly Above the North Pole

Polaris sits nearly in line with Earth’s rotational axis—specifically, the North Celestial Pole. Because of this, as Earth spins, Polaris stays nearly fixed in place in the sky.Distance Education APS 1110: Session 3


? 3. Other Stars Trace Circles Around Polaris

The Big Dipper is part of the constellation Ursa Major, which lies fairly close to Polaris in the sky. As Earth rotates, the stars in Ursa Major appear to circle around Polaris, much like the hour hand of a clock moving around a center point.Celestial Sphere | HomeofPhysics Wiki | Fandom big dipper supposed to be upside down ...


4. This Is Why the Big Dipper’s Orientation Changes

Over the course of a night—or over months—the Big Dipper seems to shift position: rising in the northeast, arcing high overhead, and setting in the northwest (in the Northern Hemisphere). But it’s always tracing a circle around the North Star.


So the rotation you observe is a direct result of Earth spinning, with Polaris acting as a relatively fixed anchor due to its alignment with our planet's axis.

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