Seeing (Level 7)

The Remains of an Ancient and Departed Sequoia
"If a tree falls in a forest and no one is around to hear it, does it make a sound?" This is an interesting philosophical riddle that probably dates to the mid 1800s in its modern English-language form. Certainly similar riddles date back many centuries in other cultures, probably as long as recorded history. To me, the answer is simple. Since sound is a perception and no one was around to hear it, the tree did not make a sound. (That answer also assumes there were no other animals capable of perceiving sound around, which is highly unlikely.) Color is also a perception, so I like to ask students if the tree has a color. The answer is still "no". This image is of a fallen giant sequoia tree in California's Sequoia National Park. Giant sequoias are the world's largest trees in terms of total volume and grow to typical heights of 165-280 ft. (50-85 m). They are thought to essentially live forever with the oldest measured specimen being over 3500 years old. Their wood is very resistant to decay and fire and it is thought that the only way a sequoia dies is that it is knocked over. Since their wood and bark is brittle, they tend to shatter when they fall, as shown in the picture. Imagine the sound!

If No Light Falls On an Object Does It still Have a Color?

Like the philosophical question about the sound of a tree falling in a forest, this is a question of perception. Since color is a visual perception and light is the stimulus that produces visual perception of objects, then with no light there is also no color. At least there is no color that belongs to that object. We might still perceive color due to the dark noise in our visual system. For example, when we are in a completely darkened room for a long period of time (so that we completely adapt), the perception is not one of black (which only exists as a related color), but one of a noisy (or grainy) dark gray.

It is, of course, possible to perceive color without visual stimulation, but such colors would not be associated with specific objects in our environment since we couldn't see them. Dreams are one example. We can have clear color perceptions of imagined objects when we are dreaming. And, yes, people do perceive dreams in color. Although for some people it is difficult to recall dreams and some people do claim that their dreams are only in black and white. Another non-visual color perception comes from pressure on the eye. If you press gently at the corner of your eye you will see some bright flashes due to this pressure. These are known as pressure phosphenes. It is not very good for your eyes to press on them, so I don't recommend doing this experiment more than once and even then be very gentle. One could also consider afterimages as non-visual color perceptions since they result from the removal of the light stimulus rather than its presence. However, they are really still produced by visual stimulation.

These types of questions can never be answered definitively. That's what makes them philosophical in nature. It is fun to ponder them and discuss the possible answers with others. Such thoughts and discussions can lead us into greater insights about ourselves and the world around us. Another one to ponder from The Gateless Gate ... "The wind is flapping a temple flag, and two monks were having an argument about it. One said, 'The flag is moving.' The other said, 'The wind is moving.' They argued back and forth but could not reach the truth. The sixth patriarch said, 'It is not the wind that moves. It is not the flag that moves. It is your mind that moves.' The two monks were struck with awe."

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Ever wonder ... How does light affect how bright a color appears?


Updated: Aug. 9, 2010