Saturday, March 13, 2010

Fire from the Eyes

We take for granted that our experience of vision results from the interaction of light with objects. It’s obvious, isn’t it? Light shines on objects, bounces off them, and then it stimulates our eyes.

But for thousands of years, that basic concept was not understood. People only knew was that there was some sort of connection between the eyes and the objects seen. During the time of Aristotle in the fourth century BC, one school of thought held that the eyes emitted a visual fire that traveled to the object and somehow massaged it. Others believed that objects gave off a substance that flew toward the eye.

These notions persisted until the time of Leonardo, who objected to the idea of fire from the eyes. He said there wouldn’t be time, after opening the eyes, for the fire to leave the eyes and travel all the way to a distant object and return. Others reasoned that if the objects gave off a flaming substance, why can’t we see at night?

The breakthrough came from an Arab physicist Alhazen around 1000 AD, who noticed that light traveled into the eye and caused it pain. He also noticed that we experience afterimages after looking at bright light. Light—not just our eyes, and not the objects themselves—was the agent of vision.

What I wonder as I reflect on these ideas is what was the ancient conception of light? It's mentioned often in the Hebrew bible, of course. Surely the ancients were sensitive of the action of light around them. How they regard it differently if they didn't understand its role in vision?
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Based on material from Vision and Art: The Biology of Seeing, by Margaret Livingstone.
Image from Discover.

14 comments:

Erik Bongers said...

Alhazen's story is quite an interesting one. Worth reading about.

Cacodaemonia said...

I understand that there are still a few small tribal societies in isolated parts of the Amazon that have had little contact with the outside world. I wonder what their perception of the properties of light is?

Jeff said...

Interesting post Jim - thanks! My Dad is an optometrist and as an artist I've been pretty interested in the physiology of sight. As I recall there are even differences between male and female eye physiology; men have more rods and see movement better while women have more cones and see color better (hope I got my rods and cones right). Looking forward to reading the article!

Justin M. said...

I love reading about classical scientific thought! Helps shed light on our own process of conceptualization and should humble us all. It's a curious thing to read old accounts and speculations yet even curious-er when their speculations are completely wrong yet their ideas still worked for all practical purposes (how many things do we take for granted today, for simplicity, yet are way off track)!

Sadly, the "fire from the eyes" idea was bound to break down. Even the best scientific minds came up with ideas like flogiston, practical cold fusion, and dark matter.

Murat Kayi said...

There's also a simple physical observation which should have ruled out the eye-fire theory: the angle of incidence is the same as the angle of reflection for example when you bounce items off a wall.

Things would turn invisible when watched at any other than a 0° angle!

Don Cox said...

Radar, on the other hand, does work by sending out rays which bounce off objects. And you could argue that a man carrying a torch does do what they thought the eyes did.

One could imagine an alien with light-emitting organs next to its eyes. The ones on deep sea fishes are probably not bright enough to serve as lamps.

James Gurney said...

Don, good point--reminds me of the way we draw monsters and T.rex with glowing red eyes--which of course wouldn't be able to see anything in the conventional way.

Murat--you're right. I wonder what it would be like if we could go back like Twain's 'Connecticut Yankee' and describe our understanding of physics, physiology, and geology to the ancients. They would think we are crazy!

Courtney Autumn Martin said...

Hi James,
I just wanted to say how much my husband Adam & I enjoyed your presentation at the Rockwell Museum on Saturday--thanks again for signing our books!

I've been a fan of Gurney Journey for some time now and your posts are always invaluably insightful.

Your dedication to research and understanding art is truly inspiring and I appreciate the time you take to share your vast wealth of knowledge with us artists out there.

To put it simply: Thanks for being awesome. :)

Best,
-Courtney
www.c-a-martin.com

Michael said...

It's so amazing to read about the ancient perceptions of light and nature. It gives a new depth to all of the paintings and sculpture's we've seen before.

My Pen Name said...

"which of course wouldn't be able to see anything in the conventional way."
I don't know, sometimes cat's and other preditors eyes appear to glow' in the dark. rarely but light eyed people do appear to have 'glowing' eyes.


Art STudent's league lecturer Frank Porcu mentions that up until the rennaissance they percieved the body in ...four ( i think parts) the base animalistic part was around the loins (for obvious reasons ) the organs lower organs base emotions, the heart and upper body the higher emotions until the pure spirtual ones were in the head.. or something like that.. will have to dig up my notes.

Melissa Dow said...

Plato seemed to have a pretty good idea that light is necessary for vision, even though light itself is not the object of sight. He says in The Republic that "Unless there be a third nature [i.e. light] specially adapted to the purpose [of seeing], the owner of the eyes will see nothing and the colours will be invisible. . . . Light makes the eye to see perfectly and the visible to appear . . . The eyes, when a person directs them towards objects on which the light of day is no longer shining, but the moon and stars only, see dimly, and are nearly blind; ... but when they are directed towards objects on which the sun shines, they see clearly and there is sight in them."

Justin M. said...

@ My Pen Name Is:
The effect you are referring to is called eyeshine yet the phenomenon behind it is caused by light amplification within the eye of an organism with a tapetum lucidium layer. This layer of tissue increases light availability to photoreceptors allowing what we refer to as night vision!

Look either one up on Wikipedia or if you're feeling particularly masochistic, Pubmed.

So your comment is, in fact, correct! Many organisms eyes do glow with a sort of fire that allows them to see... in a round about way.

James Gurney said...

Justin--you're right, and it reminds me of seeing a cat or a raccoon from a car at night. Maybe that's where the "eye fire" idea came from.

James Gurney said...

Melissa, thank you. That's a very helpful reference. And Plato's Allegory of the Cave, after all, is all about the blinding effect of outdoor light on the eyes, compared to the illumination of caves. So maybe the notion I've presented in the post is oversimplified.