The Galileo Affair was Never About the Shape of the Earth

Flat-Earthers often bring Galileo into the discussion. They treat him as a ‘villain’ who supported the spherical Earth but unable to prove it as he failed to demonstrate the occurrence of stellar parallax.

They are wrong. The Galileo affair was in fact not about the shape of the Earth at all. It was about geocentrism vs. heliocentrism. Everyone involved already knew that the Earth is spherical.

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The Dip of the Horizon

There are two kinds of the horizon:

  • Astronomical horizon: the horizon at the eye level.
  • True horizon: the line that visually divides the Earth and the sky.

Because the Earth is a sphere, the true horizon always lies below the astronomical horizon, or the eye-level. The higher the observer, the larger the dip of the horizon.

Flat-Earthers claim there’s no dip of the horizon. They are wrong. It is not hard to observe the drop of the horizon and prove the curvature of the Earth.

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Common Sense: Not a Reliable Indication of Truth

Something would ‘make sense’ if it appears to be correct according to our personal experience. But common sense can be deceiving.  Common sense relies on our own experience which has a very limited scope. For a lot of things, our common sense is not a reliable indicator of truth.

Perpetrators of flat-Earth often exploit the shortcoming of our common sense. They would say something like “It looks flat, so it must be flat!” Some of us fell victim to this scheme and would make the conclusion from a mere hunch in place of more thorough and exhaustive observations.

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Galilean Moons: The First Objects Observed to Orbit Another Object

Jupiter possesses four large moons: Io, Europa, Ganymede, and Callisto. These are called the Galilean Moons. They are easy to observe and the first objects found to orbit a planet other than the Earth.

Flat-Earthers are often seen demanding proof that an object can orbit another object. All they have to do is to use a telescope to observe Jupiter and its Galilean moons.

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Fraunhofer Lines

Sunlight can be broken into its constituent colors using a prism. The colors are the optical spectrum of the Sun. They are the same colors on rainbows. On careful observation, the spectrum is not perfectly continuous, but it has dark lines scattered over the entire spectrum. It turned out that from the lines, we can tell the composition of the Sun without physically getting there.

Some flat-Earthers think that it is impossible for us to determine the composition of the Sun, as it is impossible for anyone to visit the Sun without getting roasted in the process. They are wrong. The composition of the Sun can be determined from the spectral lines, or more specifically for the Sun: the Fraunhofer lines.

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Crow’s Nest on Ships

A crow’s nest is a structure in the upper part of the ship, especially old-fashioned ones. It is used as a lookout point and positioned high above to increase visibility over the curvature of the Earth.

On the deck of a ship 4 m (13 ft) above the surface of the ocean, an observer can spot a 20 m (66 ft) high ship from at most ±25 km (16 mi). On the other hand, from a 35 m (115 ft) high crow’s nest, an observer will be able to spot the same ship from ±40 km (25 mi) away.

On modern ships, the role of a lookout is replaced by radars. And for the same reason, a radar is positioned in the upper part of a ship.

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Shadow on Clouds

Before sunrise or after sunset, the Sun is below the horizon and not directly visible. But the sky and clouds above are illuminated because they are high above, and sunlight can reach them.

If there’s a mountain between the Sun and the clouds, it can cast a shadow on the clouds. The flat-Earth model assumes the Sun is always high above, and thus, this phenomenon cannot possibly occur in a flat-Earth.

The fact that a mountain can cast its shadow on clouds far above it is evidence that the Earth is spherical.

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The December Solstice: When The Sun Illuminates An Impossible Shape in the Flat-Earth Model

The December solstice occurs between the 20th and 22nd in December, which is when the Sun reaches its most southerly excursion. Around this time, the northern hemisphere experiences winter, and conversely, the southern hemisphere experiences summer.

If we try to plot the areas that are having daytime and nighttime on the so-called ‘flat-Earth map’, the Sun would appear to illuminate an impossible area, similar to Batman’s bat-signal. This fact tells us that the ‘flat-Earth map’ does not conform with reality.

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