\nIf a tree falls in a forest and no one is around to hear it, does it make a sound? Philosopher George Berkeley asked this famous question in 1710, and people are still debating it. Where is the forest located. How is sound defined? What...\nIf a tree falls in a forest and no one is around to hear it, does it make a sound? Philosopher George Berkeley asked this famous question in 1710, and people are still debating it.
Where is the forest located. How is sound defined? What do the words “no one” mean? Three things are needed to make a sound. A vibration, a medium through which the vibration can propagate, and a receiver to measure that a sound was made.
Sounds are waves of high and low air pressure called compression and refraction. The amplitude of the wave determines how loud the sound is. And the frequency of the waves determines the pitch that we hear. These waves of pressure enter our ear canal, which vibrate our eardrum which transfers this vibration to 3 tiny bones in the middle of our ear, which in turn transfer the vibrations to the cochlea. These vibrations result in an electrical signal carried by the auditory nerve to the auditory complex of the temporal lobe of the brain. It is here that the electrical signals are processed, and allows us to hear things.
The frequency of sound that our brains can interpret however is limited to 20Hz to 20kHz. One hertz just means one cycle per second. IS sound only a sound when a person hears it? If no person is around, the sound can still be perceived by animals. Other animals hear sounds using the same mechanism as us. In many cases their hearing is actually more acute than ours. Dogs for instance, can hear sounds more than 45Khz.
What if we take all the animals out of the forest? There are still millions of insects in the forest that can definitely hear sounds. A fly for example, can hears sounds of 50Khz.
What if we take all the creatures from the animal kingdom out of the picture, including all the insects in the forest? But there are other trees. In a 2014 study published in the California Academy of sciences, It was shown that plants can detect and respond to sounds. It’s been theorized that sounds could trigger a response via mechanoreceptors, or fine hairlike structures.
There are also trillions of microscopic life forms like bacteria. In a 2016 study by Shaobin Gu et al, experimental results showed that E. Coli bacteria exposed to sound waves had a faster growth rate compared to the control group. Is this not evidence for a kind of “hearing” of sounds by bacteria?
Let’s take all living things out of the forest. Maybe it is lonely tree in the middle of a desert with no other life forms. When it falls, air is disturbed, and sand is disturbed. A large tree would likely create extremely low frequency sound waves, which can travel very large distances. In fact, sonic waves with a frequency below 20 hz are imperceptible to the human ear. But elephants can hear them over 15 miles away. If the tree was located in a forest in Africa or jungle in Asia, an elephant might hear the sound.
Let’s take all elephants away. Then the sand was disturbed, the air was disturbed. It turns out that if the air is disturbed, the micro disturbance of the air, particularly if there are no structures to absorb the sound, could travel far.
Let's eliminate all living things within a 100 mile radius of the tree. The leaves of the fallen tree will be disturbed. And given what I said above about plants being able to perceive sounds, the tree itself will “hear” its own fall. But let’s go even further and say that this was a dry dead tree in a desert with absolutely no living thing nearby for over a 100 miles radius.
The potential energy of an upright tree was converted to kinetic energy. And this kinetic energy was converted to disturbance in the air and ground, and the sound hitting the ground would propagate through the earth. If the question is interpreted as “did” the tree make a sound vs. “does” the tree make a sound. It definitely did make a sound. But nobody was there at the time to perceive the sound. However, if a scientist is allowed on to the scene and is asked whether the tree made a sound. He would be able to ascertain from examining the changes in the sand, and the tree, that indeed the tree must have fallen, and made a sound.
Let’s make the tree free floating in space with no air and no ground. Since there is no medium such as air or ground to carry the sound, the kind of sound that we humans or animals or living things on earth may recognize did not get made. So, it made no known sounds that we are aware of. #arvinash #ifatreefalls But did it make a different kind of sound? By moving the mass, we have made a change in the gravitational bending of space that surrounds this tree. And we have added kinetic energy to the tree, which also affects space time. If we had sensitive enough instruments, we could detect this difference in the gravitational disturbance made by the tree. This instrument would allow us to “hear” the tree even in space. \n
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