Due to Earth’s axial precession, the positions of Earth’s celestial poles shift gradually in a cycle of approximately 26000 years. These days, Polaris is very close to the north celestial pole. However, 2000 years ago, Kochab is much closer to the celestial pole than Polaris. In the next 2000 years, Errai will replace Polaris as our pole star.
Flat-Earthers claim that the stars are always in the same position proves the Earth is stationary. They are wrong. By observing old star charts from a few centuries ago, the shift of celestial poles can be determined. It proves stars are not always in the same position as today, and that the Earth is rotating.
Continue reading “Old Star Charts and Earth’s Axial Precession”
Generally, sunlit objects are far brighter than any stars. It is the reason stars are not visible in a lot of photographs showing sunlit objects unless the objects are overexposed and made much brighter than the correct exposure.
Flat-Earthers take the lack of stars in photographs as evidence of misconduct. They are wrong. If the primary object in the picture is sunlit, then in most cases, stars will not be visible.
Continue reading “Sunlit Objects and Visibility of Stars”
We can determine if a star is visible from a specific location using the declination of the star and the latitude of the observer, subject to other conditions like observer’s topology, the magnitude of the star, weather conditions, etc. It is possible to do this because Earth is a rotating sphere.
If the Earth is flat, every star would have been visible all night from every location. We don’t see the same stars every night because some of them are below the horizon and obscured by the Earth.
Continue reading “Determining the Visibility of a Star From Its Declination and the Observer’s Latitude”
Some flat-Earthers like to observe celestial phenomena and the positions of celestial objects. Sometimes, they insist such events cannot possibly happen if the Earth is a sphere orbiting the Sun, and took the wrong conclusion that the Earth must be flat.
We can try asking them the time of the occurrence and the position of the observer, then use Stellarium or similar applications to simulate it. If the result matches the observation, then they have nothing to complain about. Their confusion was only the result of their ignorance.
Continue reading “Stellarium”
In astronomy, a celestial coordinate system is a system for specifying positions of celestial objects like satellites, planets, stars, etc. The origin of the coordinate can be anywhere, including Earth. If the coordinate system is Earth-centered, we call it a geocentric coordinate system.
Flat-Earthers are often triggered by the term ‘geocentric’. They would search inside astronomy books and scientific journals to find the word ‘geocentric’. If they can find it, they would use the fact as ‘evidence’ of geocentrism, or that the Earth is the center of the universe, and the Sun is revolving around the Earth.
They are wrong. In many cases, the term ‘geocentric’ refers to the origin of a coordinate system. And it has nothing to do with whether the Sun revolves around the Earth or the other way around.
Continue reading “Geocentric Coordinate System Does not Imply Geocentrism”
A circumpolar star is a star, as viewed from a given latitude on Earth, that never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars stay up there in the sky, even during the day.
Flat-Earthers claim the Earth is stationary because the same stars are always visible in the sky. They are wrong. Only circumpolar stars are always in the sky. There are others that are not circumpolar. Some are only visible during certain times in a year.
Continue reading “Circumpolar and Non-Circumpolar Stars”
Astrolabe is an astronomical instrument for measuring the altitude of the sun or stars, and to determine the solution of various problems in astronomy, time, and navigation. Astrolabe was used from classical antiquity, about 2nd century BC, until the age of discovery where it was superseded by the more accurate sextant, star charts, and time-keeping devices.
Flat-Earthers claim that astrolabes can only work because the Earth is flat. They are wrong. Astrolabes were designed using the spherical Earth model. To use an astrolabe, a good understanding of the spherical Earth model is required.
Continue reading “Astrolabe”
We can’t observe stars moving relative to each other, and the shape of constellations looks the same every night. The reason is not that stars are stationary, but their motions are very slow and cannot be observed over the timescale of human life.
Flat Earthers claim that the fact constellations don’t appear to change as proof the Earth is stationary. They are wrong. Stars have proper motion, but they can only be observed using precise instruments over a long time. Constellations do change, but the change is slow and cannot be perceived over the timescale of human life.
Continue reading “The Change of Constellations”
Polaris is a bright star that is close to the north celestial pole. Currently, Polaris is only 0.74° apart from the north celestial pole and the only star visible to the naked eye that is close to the celestial pole. This is why Polaris is popular as a navigational aid in the northern hemisphere.
Some flat-Earthers think that Polaris is stationary and that it is a ‘special star’ because other stars are in motion around it. They would take that as ‘evidence’ that the Earth is motionless. They are wrong. Polaris is merely a regular star, just like the others.
Continue reading “Polaris is not Stationary in the Sky”
If we look south in any location in the southern hemisphere, we are going to see the same set of stars. The stars are seen rotating around the south celestial pole, in the Octans constellation, nearby the star Sigma Octantis.
This phenomenon is unexplainable in the flat-Earth model. Looking at the so-called ‘flat-Earth map’, we should see the different set of stars on the different location in the southern hemisphere. The reason is that the so-called ‘flat-Earth map’ does not represent the real Earth.
Continue reading “Stars in the Southern Sky: Evidence That the Earth is a Rotating Sphere”
Diurnal motion is the apparent daily motion of stars around the two celestial poles due to Earth’s rotation. The stars move in a peculiar way that can only be explained in the spherical Earth model.
All the differences of diurnal motion that occur in the different latitudes on can never be explained in a flat Earth.
Continue reading “Diurnal Motion – Possibly the First Evidence of Spherical Earth”
Anyone who is in the northern hemisphere can observe the star Polaris, located very close to the north celestial pole. As a result, when observed casually, Polaris appears practically stationary in the same position.
Flat-Earthers claim that the fact Polaris appears stationary as ‘evidence’ that the Earth is stationary: if the Earth is in motion, then Polaris should appear in motion too. They are wrong. Polaris appears stationary because it is very far and its motion can’t be visually observed in the scale of a human life.
Continue reading “The Distance to Polaris”
Proper motion is the apparent motion of stars, caused by the movement of the stars themselves, relative to the solar system. Stars will appear to shift over time, relative to other, more distant stars.
Flat-Earthers assume stars are only in motion around Polaris, or the north celestial pole. They are wrong. Stars have other apparent movements, one of which is proper motion.
Continue reading “Proper Motion”
In many pictures taken from space, stars are not visible, even with a dark sky. The reason is that stars are very dim compared to the primary object in the pictures. If the camera is set to take a correctly exposed image of an object that is much brighter than the stars, then the stars would not be visible in the picture. The same thing would happen everywhere, in space, or on the surface of the Earth.
Flat-Earthers often take the lack of stars as fakery. They are wrong. This is simply a limitation of any camera.
Continue reading “The Lack of Stars in the Pictures of Space”
Long before GPS, navigators used a device called ‘sextant’ to determine the angle of a celestial body. From that data, the latitude of their current location can be determined.
This can only happen if the Earth is spherical.
Continue reading “Sextant: Determining Latitude from The Positions of the Stars”
A candle gets its flame from combustion, a chemical reaction. The hydrocarbon that formed the candle reacts with oxygen, and we get carbon dioxide, water, and heat energy as the results. The oxygen is obtained from the air. If the air supply is cut off —for example by covering the candle with a glass— then the reaction will stop, and the flame goes out.
We hear flat-Earthers often claimed that it is impossible for the Sun to be in space. They said the Sun burns, and therefore it requires oxygen. Space is empty, so it is impossible for the Sun to be there. They are wrong. The reaction that is occurring in the Sun is not combustion. It works differently from what happens with the candle.
Nuclear fusion powers the Sun. It fuses hydrogen atoms into helium atoms. All the necessary component for the reaction to happen is in the Sun, and the reaction doesn’t require matters from external sources.
Continue reading “How the Sun ‘Burns’ Without Air in Space”
In each day, we can observe stars drift about 1° in their movement around the celestial pole. In a month, they will appear to have moved about 30° when observed at the same time in the night. And in a year, stars are back to their original positions precisely a year before. This annual stellar motion is the basis for the calendar system we are using.
Some flat-Earthers think we see the same star constellations every night. From this assumption, they would conclude the Earth is stationary. But their claim is demonstrably wrong. Continue reading “Annual Stellar Motion: Evidence of Earth’s Orbit Around the Sun”
Stellar parallax is the apparent shift of the position of any nearby star against the background of distant stars. It is the result of Earth’s orbital motion around the Sun. It is so small and hard to observe. Successful measurement of stellar parallax was done only after the 19th century.
Some flat-Earthers presume as if stellar parallax has not been successfully observed, and use it is ‘evidence’ the Earth is stationary. They are wrong.
Continue reading “Stellar Parallax”
Flat-Earthers often claim that the fact Polaris not appearing to move is ‘evidence’ that the Earth is flat and stationary. If the Earth is a rotating sphere, then Polaris —as they say— should appear to be in motion.
In reality, Polaris is indeed moving across the sky. Though it is not something we can observe in a single night, or even in our entire lifetime.
Continue reading “Polaris: Our Current North Pole Star, But Not For Forever”
In the northern hemisphere, if we look at the sky to the north, we can observe stars rotate counter-clockwise around a point. This axis of rotation is not visible from observers in the southern hemisphere.
On the other hand, in the southern hemisphere, if we look at the sky to the south, we can observe stars rotate in the opposite direction. Conversely, this axis of rotation is not visible from observers in the northern hemisphere.
This motion of the stars cannot possibly happen in a flat-Earth. The motion of the stars is a proof that the Earth is round and rotates around its axis.
Continue reading “Star Trail: Evidence the Earth is a Sphere and Rotating Around Its Axis”