Frame of Reference

A frame of reference consists of an abstract coordinate system and the set of physical reference points that uniquely fix the coordinate system and standardize measurements. Speed or velocity is relative to a frame of reference. It is possible that two speeds/velocities are measured relative to a different frame of reference and thus cannot be directly compared.

Flat-Earthers would often compare two different speed measurements like an airplane moving at 900 km/h (560 mph) and Earth’s surface near the equator at 1674 km/h (1040 mph). They would conclude the airplane should not be able to catch up with Earth’s surface and would not be able to land if the Earth is rotating. They are wrong. The speeds are measured relative to the different frame of reference, and therefore, cannot be compared directly.

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Determining the Visibility of a Star From Its Declination and the Observer’s Latitude

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.

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Earth’s Atmosphere Rotation

Earth’s atmosphere is part of the Earth. It practically follows Earth’s rotating motion like the rest of the Earth. Due to various factors, Earth’s atmosphere has relatively small and uneven movement relative to the surface. We call it ‘wind.’ The fastest wind ever recorded is about 408 km/h, relative to Earth’s surface.

Many misconceptions about Earth arise from the wrong idea that only Earth’s solid body is rotating, but the atmosphere is not. If it is true, then we should always feel the wind with the speed of 1674 km/h near the equator, or more than 4× the fastest wind ever recorded. We don’t feel such a wind, and thus we know our atmosphere is moving at practically at the same speed as Earth’s surface.

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Geostationary Satellites

If a satellite has the orbit of 35786 km above Earth’s surface, the satellite will be in motion at the same speed as the Earth’s rotational rate. As a result, the satellite will appear practically motionless when observed from the surface. Many communication satellites reside in this orbit, and a satellite dish receiving signals from the satellite does not have to track the satellite.

Flat-Earthers often take the fact that satellites are in motion and most satellite dishes have a fixed direction as ‘proof’ the dishes cannot be pointing to satellites. They are wrong.

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The Length of Daytime and Nights in the Flat Earth Model

The majority of the flat Earth models place the Arctic Ocean in the middle of the flat Earth, and Antarctica at the edge of it. The Sun is pictured floating and moving in a circle above it. The Sun’s area of light is limited to a circular area below it, like a spotlight.

A problem: a simple observation of day and night cycles in a different area of the world cannot be explained in this flat Earth model.

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