'Spotlight' effect
« on: August 05, 2019, 07:35:26 PM »
Under this section of FW Wiki it states the following:

The apparent view of rising and setting are caused by perspective, just as a flock of birds overhead will descend into the horizon as they fly into the distance.

Same principle can be applied to an aircraft. Lets say it is flying level at 35,000ft. If seen passing through the observers zenith or overhead point, the distance between the observer and the aircraft will be as stated, 35,000ft will it not. To the pilot, situated 35,000 ft directly above the observer, the horizon is 229.3 miles away according to To the observer on the ground however, lets say they are 6ft tall, the visible horizon to them is only 3 miles away.

If RE is correct and the aircraft is flying level w.r.t the surface (constant height) then the aircraft will follow a curved path which remains parallel with the circumference of the Earth. That would mean I would have thought from the observers point of view as the angle between the aircraft and the observer changes, so it would appear to sink lower and lower in the sky until it meets the horizon. The higher the aircraft the longer it remains in the observers line of sight.

If the Earth is flat then I would suggest for a given height the aircraft would remain in view for a much longer time than it does in the real world because the path of the aircraft and the surface of the Earth would be straight, parallel lines and so in effect the aircraft would never actually reach the horizon let alone disappear below it. Only the limits of the transparency of the air would limit the visibility of the aircraft.

How long does the ISS remain visible from the same observation spot assuming it passes through the zenith?


Offline Zonk

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Re: 'Spotlight' effect
« Reply #1 on: August 05, 2019, 08:32:14 PM »
Only the limits of the transparency of the air would limit the visibility of the aircraft.

That of course seems to be their argument.  But it doesn't pass the small test.  They will claim that the observer on the ground can see only 3 miles is because that's as far as the light can travel parallel to the ground, and one can see tall objects, or those in the sky much further away because they are higher.  A light beam traveling 230 miles from 35,000 feet to the ground describes an angle of 1.6 degrees.  At 3 miles from the observer, that light beam is a mere 454 feet above the ground.  The transparency gradient of the atmosphere cannot be so steep as to totally block a light beam at the surface at 3 miles distant while allowing it to travel 230 miles if it is 450 feet above the ground at the same distance.  Especially given that those numbers hold no matter what elevation the ground is. 


Re: 'Spotlight' effect
« Reply #2 on: August 05, 2019, 08:44:31 PM »
I got my words a bit mixed up there.  What I meant to say was only the limit to the visibility of the aircraft would be the transparency of the atmosphere. 

My point essentially is that a visible and clearly defined horizon in itself provides evidence that the Earths surface is curved. A flat Earth would not have a horizon in the same way. The surface would gradually become more and more indistinct as the effect of the air quality gets greater and greater with increasing distance.  You wouldn't get a sudden cut off as you do in the real world. The higher the observer the further away the horizon. As you get higher the effect of atmosheric scattering also increases which is why you cease to get a clear and distinct horizon above a certain height. that effect will inevitably vary with air quality.

There is certainly a perspective effect in RE that makes aircraft (or indeed birds to use the example of the FE Wiki page) appear to get lower and lower in the sky as the angle between the object and the observer changes.  So that cannot be used to 'evidence' the case for FE.
« Last Edit: August 05, 2019, 09:19:09 PM by newhorizons »