Search Results for: frame of reference

Frame of Reference

A frame of reference consists of an abstract coordinate system and physical reference points that uniquely fix the coordinate system and standardize measurements. Speed or velocity is relative to a specific 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 like to 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 land if the Earth is rotating. In reality, both the speeds are measured relative to a different frame of reference, and therefore, cannot be compared directly.

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Velocity is Measured From Specific Frame of Reference

A widespread misunderstanding within the flat-Earth victims is related to velocity/speed. They seem to think velocity is absolute, while in reality it is measured from a specific frame of reference. Example:

“If the Earth is in motion around the Sun at 30 km/s, and Apollo traveled at only 11 km/s, then how could Apollo astronauts possibly make it back to the Earth?”

We used to measure velocity/speed relative to the surface of the Earth. But it is not always like that.

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Weightlessness, Free Fall, and Microgravity

In orbit, objects are weightless because both the objects and the spacecraft have the same speed and direction, and both are affected by the same gravitational influence. We use the spacecraft as the frame of reference. Because the objects are not in motion relative to the spacecraft, they appear to float.

In Earth orbit, the objects are still affected by Earth’s gravity, but yet they float. Flat-Earthers use it to disprove spaceflight. In reality, the objects float because we are using the spacecraft as the frame of reference, which is also moving by the same amount and is affected by the same gravity as the objects themselves.

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Fictitious Force

A fictitious force is a force that appears to act on every object when the frame of reference is accelerating. The term “fictitious” does not mean the force does not exist, but it is not an actual force that arises from an interaction between objects.

Flat-Earthers noticed gravity is considered a fictitious force and use the fact to “prove” gravity does not exist. In reality, we can feel a fictitious force. It is merely a term we use for forces that arise due to an accelerating frame of reference.

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Coriolis Effect

The Coriolis force is a force that acts on objects that are in motion within a rotating frame of reference. Because the Earth is a rotating sphere, an object traveling unattached to Earth’s surface is affected by the Coriolis force, depending on its speed and direction, as well as its latitude on Earth’s surface.

The rotating motion of the Earth causes the different parts of Earth’s surface to have different linear speeds, depending on its distance from the Earth’s rotational axis. An object moving from a location to another with a different linear speed will be affected by the Coriolis force because the motion of the object is now being observed from another location with a different linear speed/direction relative to Earth’s rotational axis.

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Moving Vehicle Analogy and the Physical Barrier Excuse

We cannot feel the Earth rotating, and to explain the phenomenon, we usually use the moving vehicle analogy. If the vehicle is moving at a constant speed, we will not be able to sense the motion. We cannot feel the motion of Earth because of the same reason.

Flat-Earthers invented the excuse that we are standing on Earth, not inside it, to falsely reject the explanation.

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Human Perception of Speed and Acceleration

When aboard an airplane flying at cruising speed, we will not be able to feel that the plane is, in fact, moving at speed of more than 900 km/h. But if the plane changes its speed, turns or changes its altitude, we can easily feel it.

The same thing happens with the motion of the Earth. Due to Earth’s rotation, the surface of the Earth is moving at 1656 km/h near the equator. We never feel it because the speed is constant, or in other words, the acceleration is zero.

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Rebuttals to Eric Dubay’s “200 Proofs Earth is not a Spinning Ball”

Eric Dubay made the purported list of 200 “proofs” Earth is not a spinning ball. These are the list of his “proofs” and links to the rebuttals elsewhere on this website. Links open in a new tab.

This is a work in progress. New rebuttals are being added regularly.

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Apollo 8 vs Apollo 11 Earthrise Photos

A hoax in flat-Earth circles claims that Earth in the Earthrise photo taken by Apollo 8 is identical to a similar photo taken by Apollo 11. In reality, they are clearly not identical at all.

It might have been caused by an error by an online source or someone trolling flat-Earthers. However, it demonstrates flat-Earthers’ lack of critical thinking, as it can be easily shown the claim is false by finding the originals from NASA’s image archive.

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Changing Camera Zoom Changes the Exposure in Automatic Mode

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A camera in automatic mode will evaluate the entire scene and choose the exposure automatically. If the entire scene appears too dark, the camera will increase the exposure. If the entire scene is too bright, it will decrease the exposure.

If the intended object is small, bright, and on a dark background like a sunset, changing zoom will affect the overall brightness of the entire scene. The automatic mode might choose an incorrect exposure. It is the source of much flat-Earth misinformation & can be corrected using manual exposure.

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Ultra Wide-Angle Lens

An ultra wide-angle lens produces images with an extremely wide angle of view. A lens with a focal length shorter than 24 mm (full-frame equivalent) is considered an ultra wide-angle lens. Ultra wide-angle lenses come in two varieties: rectilinear lens and curvilinear, or fisheye lens.

Because of their wide field of view, Earth’s curvature is easier to observe using an ultra-wide lens. Flat-Earthers incorrectly assumed it means a fisheye lens that distorts straight lines. In reality, there are rectilinear ultra wide-angle lenses that preserve straight lines. With these lenses, if the horizon looks curved, then it must be due to Earth’s curvature itself.

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Zooming-In on the Setting Sun

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Camera zoom works by enlarging the center portion of the image, or in other words, by making its field-of-view narrower. Zooming in on the setting sun will not reveal more of the sun and will only enlarge the size of the sun in the resulting image.

Flat-Earthers claim that zooming in on a setting sun will reveal the full sun and somehow lift it out of the water. In reality, they used incorrect exposure settings, making the sun still above the horizon appear already half-obscured by Earth’s curvature.

Zooming on the setting sun will never reveal the sun already obstructed by Earth’s curvature.

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Bokeh

In photography, bokeh is the way a lens renders out-of-focus points of light. The shape of bokeh depends on the shape of the lens’s aperture more than the out-of-focus objects themselves.

Flat-Earthers fail to take properly-focused photos of stars and planets because of their lack of photography skills and because their cameras are not suitable for the purpose. They are just getting bokeh, which tells us more about their equipment (and lack of knowledge) than the actual intended objects.

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Image Noise and The “Transparent Moon” Misinformation

Image noise is a random variation of brightness or color information produced by a photo film or digital sensor. Image noise is an undesirable by-product of photography and does not come from the actual objects in the picture.

Image noise can be in the salt-and-pepper type, forming bright dots in the dark parts of the image. When appearing in the dark part of the Moon, flat-Earthers incorrectly claim they are stars, “proving” that the Moon is transparent. In reality, these are just image noise, not part of the actual objects.

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Salar de Uyuni and Other Salt Flats

Salt flats are flat expanses of ground covered with salt and other minerals. Salar de Uyuni in Bolivia is the world’s largest salt flat. Salt flats appear visibly flat, but they still follow the curvature of Earth.

Flat-Earthers claim the apparent flatness of Salar de Uyuni and other salt flats “proves” a flat Earth. In reality, while salt flats appear flat, they still follow Earth’s curvature. On a salt flat, the bottom part of a distant object will be obscured by Earth’s curvature, similar to at sea.

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Observing Earth’s Curvature From a Flight

At the cruising altitude of a jet airliner, Earth’s curvature is too slight for us to notice casually. But with planning and careful observation, it is not impossible to see the curvature. Continue reading “Observing Earth’s Curvature From a Flight”

Perspective of Earth Due to Different Observer Distance

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Because of a perspective effect, an observer in space can see more of Earth’s surface if they are farther from Earth.

Flat-Earthers noticed the different visible Earth’s surface in different Earth images and used it to “prove” they are fake. In reality, it is just a perspective effect caused by the fact that the Earth was seen from a different observer distance.

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Five Photos of Neil Armstrong on the Moon

Neil Armstrong was the lead photographer on the Apollo 11 mission, and he could not be in the photos he was taking. Out of 1266 photos from the Apollo 11 mission, only five good photos of Neil were taken while Apollo 11 operated on the surface of the Moon.

Some memes humorously compare the total of five photos of Neil on the Moon to the number of selfies some ladies take in the bathroom. Flat-Earthers took them too seriously, and these became a hoax claiming that Apollo 11 brought back only five photos.

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Uniform Circular Motion

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The motion of a specific location on Earth due to Earth’s rotation is a uniform circular motion. We can separate it into a uniform linear motion and a centripetal acceleration toward Earth’s center. From the reference frame of an observer on Earth, the latter results in a constant centrifugal acceleration, which is felt simultaneously with Earth’s gravitational acceleration.

We often use the uniform linear motion of everyday objects to explain the effect (or the lack of thereof) of uniform motion of Earth’s rotation. Flat-Earthers incorrectly reject it just because “it is not a circular motion unlike Earth’s rotation” In reality, a uniform linear motion is one component of a uniform circular motion. And these explanations are correct and still apply.

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Moving Vehicle Analogy: Inside vs Outside of the Vehicle

The moving vehicle analogy is often presented to explain how Earth’s rotation does not seem to affect an object’s motion. Similarly, a ball released inside a moving vehicle will not fall rearward because it retains its inertia.

Flat-Earthers offer the moving open-air vehicle as if it is the “correct ” analogy. In reality, with their analogy, the air moves relative to the vehicle, which exerts an additional force that does not exist in the fact being explained. Their analogy fails to represent the fact being explained.

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