The Moon Terminator Illusion
The Moon Terminator Illusion

Hey, Vsauce. Michael here.
This is called the dolly zoom effect
and the optics that make it possible are also responsible for what’s called the moon terminator illusion. A terminator is the line between an illuminated and dark side.
Light arrives perpendicular to the terminator but it
doesn’t always appear to.
Maybe you’ve noticed this before. When the Moon and the Sun are up at the same time,
and a good distance apart in the sky, the direction the Moon is being lit from won’t always appear to line up with the position of the Sun.
What’s going on here? The answer lies in visual angles.
The further away from you something is, the smaller it will appear to be.
In psychophysical terms, its visual angle shrinks – the angle within your field of
view that it stretches across. Now, this means that everything
we look at is foreshortened, that is it diminishes incise towards the horizon line. A line infinitely far away.
Things that far away are foreshortened to the point at which
they have no height whatsoever.
This distortion affects everything that we look at.
But it doesn’t confuse us, because our brains know about it.
We can look at an object that is foreshortened and figure out what it probably actually looks like. For example, a door is a rectangle, but it’s wrecked by foreshortening when opened.
Closer distances appear larger. The whole shape is different, but your brain isn’t
freaked out every time a door opens, because it understands that different sensations don’t necessarily mean different actual things.
It’s called subjective constancy.
Our brains cleverly factor in previous experience and perspective clues from
the surrounding world to calculate in real time whether changes in what we sense are because of actual changes in the things we’re looking at or are
just merely products of their positions or the surroundings. For example, I, right now on this video screen, am vulnerable to foreshortening.
But I probably look okay to you.
However, if we frame in really closely and remove surrounding perspective clues,
I can be made to look weird, strange, a little scary, distended.
I’m foreshortened without the necessary tools around me for you to mentally adjust.
This is probably the crux of the Moon terminator illusion.
Take a look at this. The line where that wall meets the ceiling is a straight line.
Seriously, take a look. If you look to the left and right,
it continues to look straight and trust me, this building was built with level straight ceilings.
But that’s not what your eye senses.
A camera will help demonstrate this. It doesn’t add in the
post sensation processing that our brains do and we can also frame in to remove other
clues telling us what to think. Now, sure enough, right in front of us the line is level with the screen of the camera –
it’s a straight line – but if we move our eyes across the line,
look what happens. If I pan this way, the slope changes and now the line
appears to be going up and to the left.
And if I panned this way, the line appears to be moving
up and to the right. What’s going on here?
A straight line can’t have changing slope, that’s what a curved line does. Just like the curve we think we see
between the Sun and the Moon.
But wait. If the line between the Sun and the Moon is
curved because of foreshortening, why don’t we see lines like this one as curves?
Well, here’s a clue.
Clues. We know what rooms are supposed to look like.
We know how they’re built. We have experience with them and there are other
things in the environment helping us. But when you look at the sky,
there’s not much to help you. In the absence of clues about distance
and perspective, our brains assume that whatever we’re looking at is equidistant from us, making the sky a sort of dome surface, like a planetarium screen. The only clue we have then is the horizon,
but it’s a red herring, because the horizon doesn’t foreshorten.
It’s just a place where due to foreshortening everything becomes infinitely flat. Brian Rogers and Olga Naumenko
demonstrated that these things result in the terminator illusion by using a planetarium. They projected two dots onto its dome,
mimicking our perception of the Sun and the Moon. They’ve then asked
participants to place a third dot on the straight line connecting them. But just as in the Moon terminator illusion, people incorrectly placed the third dot.
They were influenced by a desire to stay parallel to the horizon, as if it was subject to the same foreshortening rules.
Our brains also often fail to factor in foreshortening
when it comes to crepuscular rays, light beams streaming through gaps in clouds. They appear to converge from a common point,
as if the Sun is only a few thousand meters above Earth, but, of
course, in fact, the Sun is extremely far away and these lines are actually pretty much exactly parallel. It’s true. They look like they converge
for the same reason railroad tracks appear to converge. The visual angle of the distance separating them shrinks the further down you look.
Sometimes our brains do the opposite.
They assume and consider foreshortening even when it isn’t really there, like in this illusion, where the cars seem to be different sizes but
in actuality on the page are all the same size. Everything else in
the image is affected by foreshortening, so our brains assume that the cars
are too and decide that in order for them all to have the same visual angle, which they do, the more distant ones must be literally larger in real life.
The rate at which the visual angle of something you are looking at changes as
you move toward it, or away from it, is not constant.
In order to cut the visual angle of an object in half, its distance from you must double.
That means objects really really far away require a lot
more movement to have their visual angle changed compared to nearer objects. This is called parallax and it’s a major reason moving allows us to learn so much about depth.
It’s why stuff on the side of the road whizzes is by you as you drive past,
while distant features of the landscape appear to only crawl past.
A really distant thing, like, say, the Moon, 384,000 kilometers away appears to move so little as you do, it can seem to be following you. It’s not, of course. It’s just geometry.
For the same reasons, moving a camera through space will
affect the visual angle of nearer things, like the Vsauce mug here much more dramatically than distant things,
like Jake Chudnow’s album against the wall. It is barely changing size as we move back and forth.
But unlike moving, zooming increases the visual angle of
everything equally, regardless of depth.
Notice that when zooming, the distant album grows and shrinks
right along with the mug. Now, if you move IN while zooming OUT, or vice versa, the zoom will be most apparent when looking at distant things, while the move more apparent on near things. The result can be trippy.
Here I’ve been placed where both effects cancel each other out,
so everything around me changes instead. Another great illusion that
takes advantage of parallax is the popular star field or hallway illusion. Cover the middle of the video
and you’ll appear to be moving much faster.
But you if cover the edges, you’ll appear to be moving much slower. All you’re doing is altering
the perspective clues your brain receives about movement.
The nearer stuff at the edge changes position faster
than the distance stuff way ahead. So if you cover the slow distance stuff your brain only has the faster moving stuff to
judge speed from. But cover the faster near stuff and the slower stuff becomes the new near.
Your brain assumes that you’ve slowed down. The optics and mathematics behind all of these effects were understood at least thousands of years ago. During the Renaissance, artists used that
knowledge to produce paintings that imitated reality really well.
I mean, the perspective is quite realistic. But… the renaissance? Why did it take so long for us get there? I mean, look at this pre-Renaissance painting. What the heck is going on here?
The perspective is all wrong. That’s not at all what such a scene would actually look like.
Artists and viewers contemporary to works like that saw the world just like we do, they saw foreshortening – they couldn’t help but
see it. Foreshortening is right there in plain sight. No, foreshortening is plain sight.
So, what gives? Were medieval artists all just a bunch of five year olds? No. No in the sense that the question is wrong. Realistic-looking perspective was used
way before the Renaissance. Now, it might not have always been
mathematically formal perspective, but foreshortening was understood.
Western art went from this to this, not because humans all of a
sudden became smarter, but because of a difference in desire. What to us today might look unrealistic and thus bad, was, in its time, deliberate and popular.
The shift to imitating the world mathematically,
as if seen through a window, was more about cultural interests and objectivity and the individual than it was about artists
all of a sudden becoming smarter.
Furthermore, perspective illusions shows that what we think we see isn’t always what we’re seeing. A child’s drawing may seem crude in terms of objective mathematical imitation, but there are other things about the world and our experience of it worth imitating.
Teasing out the less plainly obvious to show
something personal is sometimes even harder than following
perspective grids Picasso put it this way it: “It took me four years to learn to paint like Rafael,
but a lifetime to learn to paint like a child.” And as always, thanks for watching.

100 thoughts on “The Moon Terminator Illusion”

  1. A Kost says:

    im 7 and yesterday a kid that is in my class used this

  2. Jake Antriasian says:

    At 7:53 you said Vic’s versa. It’s pronounced vice. Not vica. I’m kind of a grammar snob

  3. Mike Myr says:

    that door illustration is so stupid idiot the door did shrink it was not an illusion. From your view point and if i measured it the door would be thinner untell it is shut that computer thing is stupid as well i can not get any closer or further away from the moon so it will always be as it is besides if that affect were true the moon would loose its sharp as your face did ,hey dumb ass take a straight ruler and put it close to your eyes then line it up with the ceiling wow no illusion there your camera trick is just a trick any camera will do. Put the ruler in-front of the camera and follow the ruler no curve there either,

  4. Littlewing6was9 says:

    So are you still buying this hypothesis? A lot has happened since this upload. Everything will come to light, be revealed. I read it in a good book somewhere…. Blessings

  5. sachin pallaw says:

    How can i get that software?

  6. Représente La nation says:

    That car illusion is a picture from my hometown

  7. hongchuan wang says:


  8. Gorzux says:

    ¿What is the name of the song at 7:20?

  9. Jesserockz says:

    0:49 is the best thing that made me laugh XD

  10. Preston Garvey says:

    Michael, Megamind's Albino Twin Brother

  11. SkippitySkoop925 says:


    ALL YOU FLAT EARTHERS (who probably think the sun is a planet) CAN GO SHOVE IT,,,

  12. Cameron C says:

    5:04 someone bumped into the right side of the mic or something lol

  13. Austine Ochieng says:

    So this came first, then sicko mode

  14. Tajpizza52 says:

    “We’re medieval artists really just a bunch of five-year-olds?”

    – Vsauce, 2015

  15. Awp Can says:

    2:41 why does he look like mega mind

  16. blue ras says:

    2:48 , vsauce is officially megamind

  17. DJ Tile Turnip says:

    What she sees

  18. IMovie Makers says:

    Like that shot from Jaws…

  19. 45 North says:

    It confuses flat earthers!

  20. SomeKid IgUess says:

    My mind physically hurts from watching this, I think I lost brain cells lol

  21. donkay productions says:

    2:35 megamind 53

  22. Cultured Individual says:

    Recessed hairline effect

  23. Abhishak says:

    My boy Travis Scott watches Vsauce

  24. raspy32official says:

    What's going on here? Really? Look, Michael either doesn't know or doesn't care about the real nature of the Moon. But this isn't the place for truth. That's not what this channel, this pop-sci community is about. It's its own culture. At this point, I'm more inclined to believe that the Moon is analogous to Eve in the sense that this 'lesser light' (Gen 1:16) has somehow been violated: And this is the trauma we still somehow sense today. The traumatized girl as depicted in Carrie, Firestarter, Stranger Things, X-Men: Dark Phoenix, etc. This recurrent theme of the manipulated violated feminine, damsel in distress, that in turn is turning those receptive to its dark lunar influence into lunatics. It's really sick stuff. Freud was right. It's all sexual.

  25. nowonmetube says:

    6:59 checkmate flat earthers

  26. kitty cat? says:

    Me: B O L D

  27. tripleur says:


  28. Haydn Anderson says:

    8:01 The final boss of YouTube

  29. burger cheese says:

    Michael looks like he plays his dreams in IMAX

  30. tehnoobwithahat says:

    Michael finna look like Megamind

  31. NASA FAILS says:

    This dude needs to stop lying. Is trying to hide the fact that sun and moon are closer to us and move above the plane. Sun doesn't go below horizon on sunset or sunrise, you can see when the is half moon and it doesn't match with the heliocentric model

  32. Doc Holliday says:

    The lord of the rings used the zoom and move trick for that really cool scene in fellowship where the road looks to stretch in front of frodo when the nazghul is about to ride down it

  33. oGrqpez says:

    2:36 , that's one big head Michael.

  34. MATT B says:

    Wow, I have the same shirt and watch…

  35. Alex's film-house says:

    when Vsauce was fun

  36. Robot Ninja says:

    That thumbnail looks like jackfilms

  37. Meska says:

    I like your G-SHOCK

  38. N Robo says:

    Mind blowing….when he gave us a clue, and the clue was CLUES. I knew this dude was special

  39. Makarov 9x18 says:

    Flat earth "rekt"

  40. deejayxcrypt says:

    …and that’s the deeper reason why industrial designer applications have view modes like orthographic , parallel , isometric or something of the kind.


  41. MutoreoCookie says:

    I can draw like a child. It's actually super easy for me

  42. ffggddss says:

    2:37 – Max Headroom is back!!


  43. Nadya Androssov says:

    Here's a clue

    C L U E S

  44. Atley Guilbeau says:

    When he was distorted, he became Megamind as a human… Michaelmind???

  45. Staying Up Late says:


  46. Megan McAllister says:

    Clicked for all the comments from my fellow geeks

  47. sûrement says:

    4:30 Flat earth confirmed

  48. Blake Wright says:

    I’ve seen like every video, including mind field and I just love you so much! But I’ve noticed you keep saying further, when I think you mean farther… I’m not that guy… but you seem like you either know the difference or would appreciate it.

  49. L TR says:

    When I was a kid I flew commercial a lot as an unattended minor. I remember looking out the window and wondering why the airplane seemed to be slowing down the higher we got, and at cruise seemed to just be hanging there, hardly moving. I knew there was an optical effect at play, but nobody was able to explain it (or even understand my question, often)…the epiphany came when I was staring out the window with the seat leaned back so that the rear of the window opening was cutting into my view. Then I realized that if I looked down, and spotted ground features I could identify and approximate the size of, I could watch them disappear right at the rear edge of the window, and imagine myself on the ground, moving that fast, like in a really fast car….finally I had the visual sensation of the speed involved. Distance from the ground plays hell with out perception of ground speed, even on a smaller scale. There is actually a formula that tells how many mph your perception is off according to how many feet above the ground you are. But I don't remember it. But if you ever get to ride in a big rig, it will be one of the first things you notice, when you get on the highway it will seem like you're going 40-45 mph but you're keeping up with traffic, and when you look you see you are doing 65-70 mph. Just being seated in a seat that's 6 feet off the ground so your eyes are 9 feet up or so knocks a good 20-25 mph off your normal car-based visual perception of speed, and you have to adjust to it. Then, when you DRIVE the truck for a month at a time, as I did, there's always a brief period of feeling like you're really flying at regular speeds when you go home and drive a regular vehicle again. Neat stuff.

  50. I be a DOCTOR says:

    1.5 thousand flat Earth retards watched this.

  51. Isimsiz says:

    Imagine your sight being delayed a second and living like that with all the humans for a day.

    To help you, I will type some things you can't do easily or disturb you with delayed sight.

    1) Typing
    2) Using computers
    3) Walking
    4) Blinking
    5) Talking
    6) Writing
    7) Driving a car/Riding a bike.
    8) Watching Vsauce
    9) Reading a book(Changing the page)

    Just imagine typing 0.1~ words per second 😀

  52. sky says:

    2:40 megamind

  53. Beanmachine91 says:

    science confirms my belief in god

  54. LamBearToe ManAndSalsa says:

    Funny, while watching this I remembered being 5 years old asking my mom why the moon follows us when we drive. She told me to shut the f*ck up and go to sleep.

  55. The Spy of the Tiger says:


  56. Ryan R says:

    I've been looking at the moons for years and never even noticed

  57. Overkill says:


    I see what you did there..

  58. Potato_Blubber says:

    im surprised that no one else has commented about megamind yet

  59. mumble says:


    Yeah, this is big brain time

  60. Brian Duong says:

    2:34 it’s big brain time

  61. Máximo Ernesti Vila Echagüe says:


    its biggest brain time

  62. Andrew KVK says:

    Presumptuous of you to assume I don't freak out every time a door is opened.

  63. eXonly 1090 says:

    I think im the first person to finally understand what vsauce said……

  64. Caden Koehl says:

    The moon Arnold Schwarzenegger Illusion.

  65. NBC PLAYZ says:

    The sun to moon line looks like a claw machine

  66. SkippitySkoop925 says:

    Moon Terminator Illusion
    Moon: I’LL BE BACK…

  67. L N says:

    0:00–0:22 sicko mode?

  68. Yeetus that fetus says:

    2:37 Oh yeah, this is big brain time.

  69. Getting Dropped says:

    2:44 big brain time

  70. Tell Me More About it says:

    Thanks for telling me I am dumb.

  71. kenivia says:

    brain.exe is not responding, if you wait, it might respond


  72. Demiglitch says:

    Up, and to the left.

    Up, and to the left.

  73. I dont know what to name myself says:

    Yeah, this is big bran time

  74. Voxel Music says:

    Michael just debunked every flat earther argument ever!! xD

  75. Just one Man says:

    At the 2:00 Mark, please don't bend your fingers like that. It's creepy, man

  76. Narcoleptic Axolotl says:

    A lot of times, these videos are intriguing, or mind-blowing. This one just annoys me.

  77. Pubert E. says:

    Pffft…He assumes that I don't freak out whenever a.door is opened

  78. Will Bill says:

    9:10 and on, probably my fav moment on Vsauce, maybe second to Michael stating that a balloon is made of matter

  79. Wolfy_677 says:

    The line between an illuminated and dark part of an object: ill be back

  80. Wolfy_677 says:

    5:19 aww man

  81. The Red Rabbit says:

    Recommended videos:

    Why Do We Dream? – Vsauce
    What's The Brightest Thing in The Universe? – Vsauce
    What is The Resolution of The Eye? – Vsauce

    What if The Moon was a Disco Ball? – Also Vsauce

  82. hollo dollo says:

    I just want to explain the reason the grass looks so distorted. The way the dolly zoom works is it is up close and then moved back and zoomed in.

    When it is up close it is basically above him so it has to look down there fore revealing pits because of that pits as well.

  83. Beeg Yoshi says:


  84. Beeg Yoshi says:

    0:53 aka being a 6’9” guy I can safely say when I look at my dick it is very small.

  85. the7thbananaking says:

    Just because the building was built with level and straight lines, doesn't mean it is currently level or straight.

  86. Ali Harman ANSARI says:

    2:43 michael's final form.

  87. Anonymous ? says:


    Not funny didn’t laugh

  88. Puff -_- says:

    Big Brain

  89. TerraStorm says:

    The moment Michael turns into megamind

  90. First Name says:

    2:37 big brain

  91. Darth Nihiluz says:

    My brain is so smart it can detect optical illusions.

  92. PTNLemay says:

    This one freaks me out. It disturbs me.

  93. Brandon Ortiz says:

    no one:
    Jacksfilms: 2:35

  94. Sean Earl says:

    How weird, a vsauce video I haven’t seen…

  95. lachie Bosman says:

    I wanna know, what happenes when light goes through my window, why are they little things floating in the light beam like wtf

  96. Gunguy says:

    the title of this video sounds like a horror-action movie combination

  97. Four is 4444 44 says:

    Você é incrível!

  98. MSM - AITEK says:

    2:34 Megamindchael

  99. Rny Estrada says:

    This is big brain

  100. J Brady says:

    I felt like I didn't fully grasp all that was being described, and I wanted to.

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