Your eyes lie

Eyes are funny things. Squishy sloshy spherical-ish blobs of mostly muscle, tissue and a lot of liquid, that can somehow produce images of the world around us. They provide your sense of sight, but they’re not totally watertight. Your eyes can play tricks on you, and even make false images when they are tired.

Eyes / via Flickr

Faking water in a desert

Look, I’m no Indiana Jones, so I don’t know the next time when my lying eyes will cause me pain, but seeing water in a desert isn’t always a hallucination caused by dehydration or other mind altering events. Mirages, such as seeing a lake far away that doesn’t exist, are optical illusions that are the result of unusual temperatures and your eye’s default settings.

Normally, the light your eyes receive travels through the air from an object in a straight line. Your brain knows this, so the image it makes interprets the direction of the incoming light and uses that to make an image of what you are seeing. In a desert, where a lake mirage might pop up to foil your quest for The Lost Ark, the ground and the surrounding air is a lot warmer than normal. This extra heat means the air on the ground behaves differently – and in the case of mirages importantly it has different refractive (bending) properties. So, light travels from the sky to the ground and is bent up towards your eye. Your eyes interpret that light as originating from the ground, so it images a blue coloured object on the ground. Before you know it, there is a lake where there isn’t. Your lying eyes almost got you killed.

Seeing Beyoncé with tired eyes

Even though I stare at images of Beyoncé most days, this image of our One True Queen is a little off, don’t you think? Turns out, our Queen Bey has been converted into something called an afterimage. If you’d like to bathe in Her glory, stare at the dot on her nose for about 30 seconds, then look away onto a white surface.

BEYONCE/ Afterimage via Flickr

Beyoncé appearing before our eyes is not a magic spell that Jay-Z has cast so that we all have Her image before us at all times, it is actually caused by our eyes getting tired.

Images in our eyes are constructed by a series of receptors called rods and cones. Rods detect in greyscale, and give us shades of light and dark, and cones detect the three primary colours, red, blue, and green.  Sometimes, images are so bright and our eyes have seen them for so long that our eyes are saturated in that colour. Those receptors are so tired, that they can’t even function for a while, especially after staring at the above image of Bey for that long. So, when you look away onto a white object (which is white because white light is made of all colours of light) the tired receptors can’t do anything and at the same time the unused receptors are trying make the white image. The tired receptors lead to an absence when your brain tries to mix all the colours, so instead of making a white light background, your brain construct the inverse image.

Our eyes are liars, so next time I see Beyoncé’s image floating in the sky, I’ll blame hot and cold air, and tired eyes.

4 Responses to “Your eyes lie”

  1. Nastasia Bartlett says:

    Thanks Marie! Glad you liked it.

  2. Nastasia Bartlett says:

    Thanks Jennifer! One of my favourite wiki pages is the list of optical illusions! You begin to doubt your brain/eye connection after viewing some of them!

  3. Marie says:

    Great post.

  4. Jennifer Feinstein says:

    Woah! What a complex topic. LOVE that you brought in Bey and that illusion blew my mind…! So impressed that you managed to make your blog post interactive! Great work.