The Moon Tilt & Terminator Illusions

[Abishua]

Flat earthers NEED to show that the moonlight isn't reflected sunlight, because if it IS, the moon phases show it is a sphere, and the lunar eclipses show that the Earth's shadow is always circular, which means that the Earth must be a sphere as well.

I ran into some cases when the lit moon does not match position of the sun.. I think if the sun is 93 million miles away seeing moon during day would be tricky.. because moon is much closer.. so would the sun not light up the same backside of the moon that is facing away from us?

here is an example where the lighted part of the moon does not match sun position so you can check it out if you want

Source: https://youtu.be/K-ZU3jTReco

[UPDATE] The odd tilt angle of the moon described in the video is an optical illusion caused by the wide viewing angle, illustrated here:
Source: https://www.youtube.com/watch?v=AI4b_TAkcoM

 

[Mick West]

https://en.wikipedia.org/wiki/Lunar_terminator#Lunar_terminator_illusion

The lunar terminator (or tilt) illusion is an optical illusion arising from the erroneous expectation of an observer on Earth that the direction of light illuminating the moon (i.e. a line perpendicular to the terminator) should correspond with the position of the sun in the sky or a sun which has set, when it does not appear to do so. The cause of the illusion is simply the observer is not taking into account that the observed slope of a light ray will change across the sky because of the lack of visual clues to establish 3D perspective.[3][4]

Content from External Source

http://chrisjones.id.au/MoonIllusion/

When the moon and the sun are both visible in the sky, but not close together, the sunlight often appears to illuminate the moon from a high angle, even when the sun is closer to the horizon than the moon.

As seen in an orthogonal projection, the lunar terminator (the boundary of the illuminated hemisphere of the moon) appears from Earth as a half-ellipse. The major axis of the ellipse is perpendicular to the sun's direction from the moon: the sun lies on an extension of the minor axis.



The illusion occurs when the moon and sun are separated by a wide angle, so that they are perceived relative to the horizon, as if in a panorama. A panoramic photograph is a cylindrical projection. In this projection, most straight lines project as sinusoidal curves. The moon-sun line is curved, unless the moon and sun are on the horizon or directly above one another.

Content from External Source

http://www.seas.upenn.edu/~amyers/MoonPaper20June.pdf

Abstract. The moon tilt illusion is the startling discrepancy between the direction of the light beam illuminating the moon and the direction of the sun. The illusion arises because the observer erroneously expects a light ray between sun and moon to appear as a line of constant slope according to the positions of the sun and the moon in the sky. This expectation does not correspond to the reality that observation by direct vision or a camera is according to perspective projection, for which the observed slope of a straight line in three-dimensional object space changes according to the direction of observation. Comparing the observed and expected directions of incoming light at the moon, we derive an equation for the magnitude of the moon tilt illusion that can be applied to all configurations of sun and moon in the sky.

Content from External Source

 

[Mick West]

You can do an experiment to illustrate this. You need two balls for the Earth and the Moon, and a relatively powerful flashlight (preferably where you can focus the beam to increase the brightness on the targets). I recommend the Duracell Durabeam Ultra, which is very bright and has great focus.

Then in a dark room (or at night outside) place the balls so they are illuminated by the flashlight at a distance (at least 10 feet). You'll see the terminators (the line between light and dark). You can then picture yourself on the surface of the Earth ball, and see what the moon looks like from that position. Remember your viewpoint will be tilted, but the key point is that you can be in daylight, and see the sun and the moon in the sky together with the sun partially illuminating the moon.

You can can them move the moon around to various positions, and observe the terminator. It's not going to be quite right because of scale, but you get the general idea. Here, I'll do it now.

 

[Mick West]

Here's that experiment in practice:
Source: https://www.youtube.com/watch?v=s5EXHJ6zeag

 

[Z.W. Wolf]

There are two flavors to this FE problem with the moon terminator.

1. The terminator is supposed (by science) to be caused by the moon being half lit by the sun.

2. The terminator is supposed (by science) to be caused by the earth's shadow on the moon.

Number two is the majority position. It took me a long time to figure that out. I'd never dreamed that anyone thought that. But it turns out that this is a common misconception among the general population.

 

[Mick West]

There are two flavors to this FE problem with the moon terminator.

1. The terminator is supposed (by science) to be caused by the moon being half lit by the sun.

2. The terminator is supposed (by science) to be caused by the earth's shadow on the moon.

Number two is the majority position. It took me a long time to figure that out. I'd never dreamed that anyone thought that. But it turns out that this is a common misconception among the general population.

I doubt the "general population" gives it much thought. I think the idea might be more prevalent in the FE community simply because a very commonly offered proof of the globe earth is "The shadow of the Earth on the moon is curved". So the FE folk think a lot about the claims of the shadow of the Earth on the moon, and that ends up with them thinking the shadow on the moon is supposed to be the Earth's shadow.

 

[Z.W. Wolf]

Those who are having trouble with number one:

When they look up at the sky they "see" a close sun. They actually make fun of ball earthers for not immediately seeing this reality.

So they are seeing the earth-moon-sun system as an equilateral triangle. In other words the moon and sun are at an equal distance from the earth. If that were true than the terminator position would not make sense. They are relying on their own perception, which is the heart of the idea.

In an intuitive manner these FE believers feel that the terminator they see not making sense in an earth-moon-sun equilateral triangle is support for the sun being close. I know that sounds confusing, but it's difficult to express this intuitive feeling in words.

 

[Z.W. Wolf]

I agree that the general public doesn't think about these things much. But when people are asked the question, for instance - "what causes the seasons?" - a large number will say that the sun is closer in summer.

According to this: http://www.npr.org/sections/thetwo-...ink-the-sun-goes-around-the-earth-survey-says

To the question "Does the Earth go around the Sun, or does the Sun go around the Earth," 26 percent of those surveyed answered incorrectly.

Content from External Source

Whether these are long standing beliefs about something they seldom think about (or have little interest in), or whether these are an ad hoc answer to a question they had never considered is an interesting question. Certainly 26 percent of the population are not dedicated geocentrists.

My source for the statement that the earth shadow terminator misconception is widespread is this single video:

It has nothing to do with the earth casting its shadow on to the moon, as is a common misconception among students.

Content from External Source

So perhaps I'm over reaching.

In YT comments sections I've also seen a couple of well meaning globe earthers saying things that show they also believe in the earth shadow terminator.

 

[Mick West]

My source for the statement that the earth shadow terminator misconception is widespread is this single video:

Right, but that's amongst students who have been asked about it. Most people have not given it any thought.

And pretty much all Flat Earthers have given it some thought.

See we are not going to fix these misconceptions in the general population unless we do it at the root, in schools. We can only try to address it now on a case-by-case basis.

 

[Z.W. Wolf]

Right, but that's amongst students who have been asked about it. Most people have not given it any thought.

And pretty much all Flat Earthers have given it some thought.

See we are not going to fix these misconceptions in the general population unless we do it at the root, in schools. We can only try to address it now on a case-by-case basis.

Yes, that's my position exactly. This whole thing is an opportunity to show what people, as a whole, are having trouble with. For example, people seemingly have a tremendous problem with Newton's three laws of motion. More effort has to be made to explain these things on an intuitive level and not just assume that people are "getting it."

 

[Trailblazer]

I think it is quite a common misconception, even among those who know the Earth is not flat. For example see this post on a debunking forum:



"He shows the shadow of the Earth on the Moon"

 

[Z.W. Wolf]

This illustrates the problem the FE believers are having with the earth-moon-sun system model. They are assuming a sun and moon at an equal distance from the earth. If the sun were at a position just off the screen to the right, the moon terminator would not make sense as we see it in the sky. The moon would be full or nearly so.

Of course they are assuming their own conclusion: a close sun.

 

[Mick West]

I was thinking about WHY the misconception (of the terminator being the Earth's shadow) occurs. It struck me that we are used to seeing a dark shadow of one object on another,


but not so much a dark shadow on the back side of a ball in sunlight.

Note there's a dark shadow on the beach, but not on the back of the ball.

The reason, of course, is ambient light. The light reflected off everything else in the scene (like the sand here), and direct light from the atmosphere (the sky) and the clouds.

Then you compare that to the moon's terminator, in the blackness of space with practically zero light for other directions.


It's a stark black shadow. And to our simple human minds it looks more like the shadow cast on the sand than the slight darkening on the back of the ball.

Of course there is a little light even on the unlit portion of the moon, mostly from the Earthlight. You can see this in a really long exposure.

Source: https://commons.wikimedia.org/wiki/File:Earthshine_Moon.jpg

 

[Trailblazer]

Of course there is a little light even on the unlit portion of the moon, mostly from the Earthlight. You can see this in a really long exposure.

And sometimes with the naked eye. I wasn't sure why it is sometimes so much more obvious than at other times, so I just looked it up. It's to do with how reflective the Earth is (obviously), which is down to the amount of sunlit ice (less obviously).

http://earthobservatory.nasa.gov/IOTD/view.php?id=83782

Earthshine varies in strength throughout the year, since the light reflected from the Earth varies. Earth’s reflected light (albedo) is brightest in the Northern Hemisphere spring with a second, slightly smaller peak in the Southern Hemisphere spring.

Satellite measurements of energy reflected from the Arctic provide a picture of why earthshine peaks in the spring. During this period, the Northern Hemisphere is tilted towards the Sun and winter snow and ice are still on the ground in the higher latitudes. Because snow and ice reflect more light than vegetation or water, the spring is brighter than the summer or autumn, when there is much less snow and ice. During the winter, the Arctic receives very little sunlight and reflects less light. Clouds and sea ice contribute to the peak in the Southern Hemisphere.

Content from External Source

 

[Henk001]

There are two flavors to this FE problem with the moon terminator.

1. The terminator is supposed (by science) to be caused by the moon being half lit by the sun.

2. The terminator is supposed (by science) to be caused by the earth's shadow on the moon.

Number two is the majority position. It took me a long time to figure that out. I'd never dreamed that anyone thought that. But it turns out that this is a common misconception among the general population.

Only a few days ago I heard about a science teacher who told his pupils that. I couldn't believe my ears...

 

[Henk001]

I was thinking about WHY the misconception (of the terminator being the Earth's shadow) occurs.

It could also have something to do with the way the moon is often depicted in children's books, like this
This suggest that something is casting a shadow on the moon, I would say

 

[Henk001]

I had a night to sleep on it and i came up with this short lecture (I am a physics teacher so you will excuse me for being a bit excessive)
First, to put things in perpective, a scale drawing of the earth, moon and the moon's orbit

The pale grey dot in the upper part of the orbit represents the moon. Now we want to add the sun. Lets reduce this picture to this and show the sun right next to it:

Now the sun's distance is about 110 times its diameter so if you want to see that in one picture you'll get this

Always keep these dimensions in mind when looking at the following.
We now are trying to see the moon's orbit in perspective, putting it in a plane and let the sunlight come from the right. Also we blow up the size of the earth and the moon:
Now look at the two blue arrows, representing the viewing directions towards the moon and towards the sun, they make an angle of 90°. The dashed circle is an arbitrary circle on which we see both the moon and the sun. Now what does this circle look like when projected on the celestial sphere -- which is, for clarity, an imaginary "sphere of directions"? First lets look at it from the standpoint of an observer close to the north pole

The sunlit half of the moon almost faces the sun
Next from the standpoint of an observer living in the mid latitudes:

remember that these 2-dimensional pictures are projections of a 3-dimensional viewing sphere.
At the equator the moon will even look like this

So, on the celestial "sphere" you have to imagine a great circle, being the section of the earth-moon-sun-plane with that sphere. The circle is tilted more or less depending on your latitude (for the sake of simplicity again I also ignore the tilt of the earth's axis and the inclination of the moon's orbit), causing this illusion.

 

[Abishua]

Ok.. I see what you guys are saying.. but lets suppose here for a second that moon is a 3d object in the sky.. out of the information the lit portion of the moon gives us we can draw an axis through the moons very center of illumination..



So my question is.. how does this happen? the illuminated part of the moon does not lie.. since moon is lets say 3d.. it shows a specific direction in space where the light source is coming from.. so what are we seeing wrong here? is the sun not where we see it, or is the moon illuminated part not what we see it is? Disregard earth for a second.. just look at where moon shows the lightsource is.. look at it as independent 3d object.. and determine the position of lightsource only by that info.. and then look where the suns position actually is..

 

[Mick West]

So my question is.. how does this happen?

The path of light from the sun to the moon is a straight line, so you'd think if you draw the line out from the moon at right angles to the terminator,then it would hit the sun.

And it actually would, if you could get them both in the same photo, taken by a rectilinear lens.

A simpler way of putting it is that the path seems curved for the same reason any long straight line looks curved in panorama photos. Consider this setup (The "sun" here is the larger globe, chosen for size, not color). The sun and moon are the same apparent size, and the line connecting them is straight.


But when they are far apart (from my viewpoint) I can't get them all in one photo. I have to take three to cover the path.


Now the line between them is no longer visually straight.

We can also take a panorama photo:


In reality we are not half-way in between the sun and the moon, we are a lot closer to the moon, so it's more like


So there is a straight line going out at right angles to the terminator from the moon to the sun. There are other factors involved - the illusion of them being at the same distance - but most of the time the angle between the moon and the sun is just too large for the whole line to fit in one photo, so it appear curved when shoehorned into a panorama or fisheye.

 

[Henk001]

Ok, let me try again to explain. Consider the celestial sphere below:

You see the half-lit moon in one direction (like southeast) and the sun under an angle of 90° (southwest).
When you look at the moon you conclude that it recieves light from the direction indicated by the dashed black arrow. Now you argue that if the moon is sunlit it should point towards the sun like the thick blue arrow.
But that is only where the sun APPEARS to be on the celestial sphere. But neither of them is actually ON that sphere. It is a sphere of directions -- not positions. In reality the sun is 400x further away than the moon. If we zoom out and put the moon and sun on distances with the right proportions we get the following picture:

In fact the sun should be -- on this scale -- about 50 screenwidths to the right. So the dashed arrow and the line of sight towards the sun, the blue arrow, ARE in the same direction. Almost, that is. They make a small angle of 0,15°, intersecting in the sun.

 

[Z.W. Wolf]

Ok.. I see what you guys are saying.. but lets suppose here for a second that moon is a 3d object in the sky.. out of the information the lit portion of the moon gives us we can draw an axis through the moons very center of illumination..



So my question is.. how does this happen? the illuminated part of the moon does not lie.. since moon is lets say 3d.. it shows a specific direction in space where the light source is coming from.. so what are we seeing wrong here? is the sun not where we see it, or is the moon illuminated part not what we see it is? Disregard earth for a second.. just look at where moon shows the lightsource is.. look at it as independent 3d object.. and determine the position of lightsource only by that info.. and then look where the suns position actually is..

As I said before your eye is assuming a close sun. You are assuming that the orange line between the sun and moon is parallel to the earth's surface. But the sun is much more distant than the moon. The orange line is on a big slant.

I'll give you an example of what I mean. This is an "Ames room":



And another:


The illusion works because our eye assumes the black line of the baseboard is straight across our line of vision, like in a normal room. But it is actually slanting away from us to the left. The little guys are farther away than the big guys.

Same thing with the sun and moon. We are assuming the sun is the same distance away and that the orange line on that YT video is straight across our line of sight. But the sun is farther away than the moon and the orange line is slanted away from us to our left.


This is what a plan of an Ames room looks like from above, and why the illusion works.


We see the dark blue ball and assume that it's the same distance away as the red ball. It looks like the light blue ball and smaller than it should.


This is what our eye is assuming about the sun-moon-earth system and what the moon phase should look like:

The sun and the moon look like they are the same distance away and that the orange line (the same one in that YT video) is straight across our line of sight. This is the moon we expect to see.

But this is closer to what is really happening:



The sun is farther away than the moon, the orange line is slanted away from us to our left, and the moon looks like this.




That the moon looks like this is actually proof that it is farther away from us than the moon is. It also explains why the much bigger big sun looks like it's the same size as the much smaller moon.

 

[Mick West]

I think there's really two illusion here, and some confusion between them.

Firstly when the sun is very far from the the moon in the sky the panorama effect makes it look like the moon is tilted

Secondly when the sun is closer to the moon the tilting illusion vanishes, but now it looks like it's not illuminating enough of the moon (because it's so far behind it).

But this is closer to what is really happening:



The sun is farther away than the moon, the orange line is slanted away from us to our right, and the moon looks like this.

This explains the second illusion. But the illusion in the video is the first one.

 

[Z.W. Wolf]

A video about the Ames room illusion:

The brain has to resolve ambiguities and in doing so it uses all sorts of assumptions... about the world. And because it uses all these assumptions... you can also trick the visual system.

Content from External Source

If you train yourself to see the sun as much farther away than the moon, the moon phase actually looks right.

 

[Mick West]

I ran into some cases when the lit moon does not match position of the sun.. I think if the sun is 93 million miles away seeing moon during day would be tricky.. because moon is much closer.. so would the sun not light up the same backside of the moon that is facing away from us?

here is an example where the lighted part of the moon does not match sun position so you can check it out if you want

Source: https://youtu.be/K-ZU3jTReco

Going back to the OP, the video is describing the moon tilt illusion, but @Abishua seems to be describing the moon phase illusion.

This photo shows the moon tilt illusion, with the yellow line indicating where the sunlight seems to be coming from. This is what the video is demonstrating.

 

[Abishua]

yes.. I see what you are saying wolf, I am familiar with that kind of room illusion, but also, the sun in the daytime, at 93mil miles away should light up mostly the "dark side" of the moon.. but in the pictures like the one Mick put above we can see 70/80% of the moon lit up! In other words.. far less of the moon should be illuminated because of suns angle because of distance..

Mick how many degrees does this panoramic image cover?

 

[Mick West]

yes.. I see what you are saying wolf, I am familiar with that kind of room illusion, but also, the sun in the daytime, at 93mil miles away should light up mostly the "dark side" of the moon.. but in the pictures like the one Mick put above we can see 70/80% of the moon lit up! In other words.. far less of the moon should be illuminated because of suns angle because of distance..

Mick how many degrees does this panoramic image cover?

The original is a 360 degree image.
https://www.eso.org/public/images/potw1218a/




So that make them 6849/16726*360 = 147 degrees apart, which is consistent with the illumination we see.

 

[Trailblazer]

And it actually would, if you could get them both in the same photo, taken by a rectilinear lens.

But it's not purely a photographic effect, because you can see it with your own eyes too. The terminator doesn't line up with the sun when you look at the moon in the sky, without a camera. It is down to the misperceptions of a "straight line" in 3D space.

 

[Abishua]

Heliocentric model complicates it all.. in my opinion.. it all ends up beeing some illusions.. refractions.. terminators.. etc.. I think it's what you see is what you get

 

[Z.W. Wolf]

But here's why neither a spherical nor a flat disk moon could work on a flat earth:

https://www.metabunk.org/flat-earth...ng-by-the-moons-appearance.t7358/#post-181049

 

[Henk001]

So that make them 6849/16726*360 = 147 degrees apart, which is consistent with the illumination we see.

Apart from the fact that you should not take the azimuthal angular distance, but the angular distance along the great circle that forms the intersection of the celestial sphere with the earth-moon-sun plane -- roughly the ecliptic.

 

[Henk001]

Heliocentric model complicates it all.. in my opinion.. it all ends up beeing some illusions.. refractions.. terminators.. etc.. I think it's what you see is what you get

Historically speaking the Heliocentric model simplified a lot of things, like the planetary movements, which were quite complicated in the geocentric (Ptolemaic) model. There are a lot of enlightening sites with animations etc. explaining all this; just one example:
http://astro.unl.edu/naap/lps/animations/lps.swf

 

[Mick West]

But it's not purely a photographic effect, because you can see it with your own eyes too. The terminator doesn't line up with the sun when you look at the moon in the sky, without a camera. It is down to the misperceptions of a "straight line" in 3D space.

It is a straight line though.

When I'm standing in my garage I see this, looking in three directions from the same spot

The hinge line on my garage door looks straight to me, because it is. In each of the three photos it's also perfectly straight. My brain synthesizes the image so I know it's a straight line. But if I look at one end it does not line up with the other. If you just look at one end or the other it does not line up.

 

[Trailblazer]

It is a straight line though.

When I'm standing in my garage I see this, looking in three directions from the same spot

The hinge line on my garage door looks straight to me, because it is. In each of the three photos it's also perfectly straight. My brain synthesizes the image so I know it's a straight line. But if I look at one end it does not line up with the other. If you just look at one end or the other it does not line up.

Yes, right. I think we are saying the same thing, I just meant you don't only see it in photos.

If I look into the top left corner of the room, the line of the ceiling seems to be angled upwards from left to right. If I look at the top right corner, the line of the ceiling seems to be angled downwards left to right.





Clearly that is actually a straight line, and yet if you projected either end off in a "straight line" then it wouldn't meet the other end.

If you imagine the moon being placed in the top left corner with the terminator perpendicular to that line then you can see that it would not point at the sun in the top right corner.

 

[Mick West]

If you have a sufficiently wide angle rectilinear lens though, it will appear straight, you just can't go much beyond 90° without significant distortion.

 

[Mick West]

You get the same thing with contrails, this one was straight:


It even appeared straight, as you could see it was made of of straight line wherever you looked. But in wide angle it's curved.

 

[tinkertailor]

Historically speaking the Heliocentric model simplified a lot of things, like the planetary movements, which were quite complicated in the geocentric (Ptolemaic) model. There are a lot of enlightening sites with animations etc. explaining all this; just one example:
http://astro.unl.edu/naap/lps/animations/lps.swf

This specific webpage helped me out a lot in the online astronomy class I took a semester ago, when I couldn't quite figure out this problem for myself either. I didn't assume the earth was flat, though. I actually ended up using our space/sky simulator software, Starry Night, and "flew" to the moon to watch the sun and really get what was going on. If it wasn't super expensive because it's connected to the college textbook racket, I'd recommend it. It really helps a LOT.

 

[Henk001]

... when I couldn't quite figure out this problem for myself either. I didn't assume the earth was flat, though. ...

And that is essentially where flat earthers go wrong. Their INTERPRETATION of what they observe doesn't match the generally accepted model, "so the model must be wrong" -- instead of "so what am I overlooking?" (and ask an expert (site) to explain).

 

[Abishua]

You get the same thing with contrails, this one was straight:


It even appeared straight, as you could see it was made of of straight line wherever you looked. But in wide angle it's curved.

but in the video there was camera paning left and right.. you said that con/chem/trail looked straight.. I think if you paned non fisheye camera to the left and right of it it would still look straight.. just like when we see it.. is this effect due to fisheye lenses? or that effect when compositing panoramic images?

 

[Z.W. Wolf]

There's an experiment we can all try that will demonstrate that sunlight and both the moon phase and terminator angle really do go together.

Put a ball on a stick, use a zoom lens, back off from the ball/stick, get the ball and the moon reasonably close together in the frame. I promise that the light and shadow on the ball will match the light and shadow on the moon.

Be sure to back away from the ball and zoom in. You want to get a large image of the moon, and keep both the ball and the moon in focus at the same time. You might have to get pretty low to the ground. A standard cell phone camera won't do.

Any ball will do, but some will probably be better than others because we are trying to catch a shadow in full daylight. I'm going to try a golf ball. I like the dimples and the white color.

Take multiple frames in different exposures. Trying to get the right one to get the moon well exposed and to catch the elusive shadow on the ball.

Don't try to get the sun in the same frame. Not necessary or desirable. We're just trying to show that the sunlight here on earth is the same sunlight that shines on the moon. It's from a distant source with parallel rays.


The moon will be good from Saturday, December 3 to Saturday the 10th. (Up during the day and not too full or too thin.)

 

[Trailblazer]

Like this:



http://www.skyandtelescope.com/astronomy-resources/what-are-the-phases-of-the-moon/