What are Illusions and Impossible Objects?


Illusions are everywhere. It’s just that we perceive them as real objects or things.

                  (upper image is used from vectorstock.com)


Everybody must have seen a mirage on a hot summer day while driving or sitting inside a car on a concrete highway road. Then, just minutes after it, looking after that water on the same place you have seen some seconds ago, you feel like a fool. You start questioning your own eye power. I just saw water here,right? Well this happens when we first time see that thing, and we ask a lots of questions. Then we come to know people call it a mirage. It’s just an optical illusion.Then we come to know that well, there is a whole physics behind it! It’s an example of total internal reflection. As you may know that it occurs due to the light being bent via refraction to produce a displaced image of the object.

Mirage By Brocken Inaglory, CC BY-SA 3.0


An illusion is something when we see, the pattern of the image is such that it gets deceptive or misleading for our brain. That means the information or image that our visual system(Brain and Eyes) perceives, creates a perception that, in reality doesn’t match the true image at all. Here the visual perspective is twisted and your brain gets tricked to see something that isn’t there at all in the first place. For instance,there is an illusion we call Zollner illusion, where the picture has parallel lines drawn in it, but our eyes see as if the two ends of the straight lines receed from each other. Here the long lines with the hatches on them don’t appear to be parallel to each other. But in reality, they are parallel.

Zollner illusion By Fibonacci – Own work, CC BY-SA 3.0


We may have heard a tons of times that nothing is impossible. But there are some objects which are actually impossible in reality. We call them impossible objects. We also call them impossible figures or undecidable figures. Because these are mere optical illusions. We represent them as 2D objects that our brain interprets instantaneously as 3D objects.

Penrose Triangle:

Penrose Triangle By Tomruen – Own work, CC BY-SA 4.0,

Physicist Roger Penrose and Swedish artist Oscar Reutersvard popularized Penrose triangle. It appears to be a 2D representation of a 3D triangle. It takes some square beams to build that. But we can’t realize properties of this 2D representation through any 3D object. That means we cannot create these types of objects in reality. Hence, we call it an impossible object. This illusion tricks the human brains and eyes. Because the visual perspective is here twisted. Therefore, it creates the deception of a 3D object that cannot possibly exist at all. Here the viewer sees that the sides of the triangle that are touching the 2D representation, are at the same distance from the viewer.

Motion aftereffect


impossible cube By 4C – Own work, based on PNG versioon, CC BY-SA 3.0,

    (image of impossible cube)

However, there are also other impossible objects such as necker cube, waterfall which are examples of multistable perception (having two valid interpretations). The waterfall illusions are illusions of movement. In this kind of illusion, when you see the waterfall image on the paper after looking at a moving object, the waterfall appears to be moving. Hence, these impossible objects are really fascinating objects that make the viewer fool as well as curious.


Spread the love