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##### Flat Earth Debate / A quick note on perspective
« on: August 15, 2008, 06:13:16 PM »
Quote

A: It's a perspective effect.  Really, the sun is just getting farther away; it looks like it disappears because everything gets smaller and eventually disappears as it gets farther away.
In one of the odder premises of Zetetic astronomy, there is an odd argument that the appearance of sunrise and sunset is a function of a trick of perspective.

It's such an odd argument, contrary to human experience and so easily debunked, that it seems to me to be worth debunking it in a separate thread.

The premise is that the sun (as well as the north star, constellations et al) only seem to precede over the horizon because of the longer angle of view lowering the star until it 'appears' to drop below the horizon.

Unfortunately, this contradicts basic math and the rules of perspective on two separate issues.

First of all - there is no 'illusion of perspective' that causes an item to 'disappear' over the horizon of a flat surface despite being there within line of sigth - neither halfway, partway, or completely.

The second is that the sun and the moon have nearly identical angular sizes - both approximately 30 minutes, or 1/2 degree, a consistent value because their orbits are sufficiently distant that the irregularities in the orbital distance have virtually no effect on their size from *our* perspective.

Unfortunately - neither of these apply to a 32 mile in diameter object a mere 3,000 miles away when overhead.

As you can see, basic trigonometric calculations show that the sun will look just like we would expect *any* large body that approaches, passes, and then retreats from our point of view to look - it will get large slowly from the distance, doubling in size as it halves it's range - reach it's maximum size of ~30 arcminutes (1/2 degree) at noon, then *rapidly* decrease in size as it retreats into the distance, rather like being passed by a rude driver in a corvette 32 miles wide. It will never have any portion of itself fall 'under' the horizon unless that horizon actually rise up to meet it - which, at 14.04 degrees inclination even half way across the earth's radius in the northern hemisphere mean only in deep valleys would this ever happen.

Nor will it get 'that' small - although it will seem to shrink to some 10-20% of it's maximum size, that is still three to seven arcminutes of size, or three to six times the size of Venus at it's brightest (at 1.1 arcminutes) - so even at midnight in the middle of winter - it would be virtually impossible to miss, racing across the sky at such speeds.

Atmospheric interference perhaps? Unlikely - remember that we *can* see the stars at night, certainly well under the 7 to 14 degrees inclination that will be the furthest the sun will 'fall' before coming back up - I just watched the perseid showers last week, and can say that even here, 15 miles outside of Indianapolis, I can see stars quite clearly  as the come over the horizon, so atmospheric interference that can't block starlight will certainly not block the stray light emitted from a 32 mile diameter bright object when scattered across an atmosphere 80 miles high.

Sadly, the perspective theory is easily debunked.

Cognitive Dissonance

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