The Big Dipper is a bright asterism in the northern celestial sphere. It is always visible north of 41°N and hidden south of 41°S. Flat-Earthers noticed that the Big Dipper is visible all year and use the fact to ‘prove’ a flat Earth. In reality, the visibility of Big Dipper depends on the latitude of the observer.
Myth 1: “The Big Dipper is in the northern celestial sky, then we should not be able to see it from the southern hemisphere.”
Answer 1: It depends on the declination of the stars, or the distance from the north celestial pole. Polaris cannot be seen from the southern hemisphere because it is very close to the north celestial pole (it has the declination of above 89°). The stars in the Big Dipper are between 46°N and 62°N. Therefore, the Big Dipper can appear fully visible from north of 28°S, and partially visible from north of 41°S.
Myth 2: “Earth is moving around the Sun. Stars should not be visible all year because we are looking away from the Sun at night, to a different direction depending on the time of the year. The Big Dipper is visible all year, so the globe model is debunked.”
Answer 2: The world is three dimensional. So are the celestial world. First, the statement is valid only to observers from north of 28°N where at least a part of the Big Dipper is circumpolar, visible all year. And second, it is valid for observers from the entire world only for stars closer to the ecliptic (the path Sun appears to take in a year). The Big Dipper is far from the ecliptic. Relative to the orientation of the solar system, the Big Dipper is “up,” not in the same plane as Earth’s orbit around the Sun.
References
- Big Dipper – Wikipedia
- Determining the Visibility of a Star From Its Declination and the Observer’s Latitude – FlatEarth.ws