Posted in Science & Nature

Silence Of The Trees

A timeless philosophical question goes like this:

If a tree falls in a forest, does it make a sound?

This may sound absurd, but the question hangs on the definition of sound. Is sound the physical phenomenon of vibrating particles forming a soundwave, or is sound the sensory information that we perceive by converting said soundwave using our hearing system? If you accept the first definition, then yes, the falling of the tree will generate energy that pushes on the air particles around it, causing a soundwave that if someone were to hear it, would sound as a “thud”. But if you accept the second definition, then that tree would not have made a “sound” per se because no one was around to perceive the soundwave. Following this logic, a sound cannot exist without a recipient to hear it.

As simple as this may seem at face value, the riddle explores some deep philosophical and scientific issues.

The most obvious one has been discussed: the definition of sound. But then one must question what would happen if a tape recorder was running when the tree fell. Can a machine hear, even though it cannot “sense”? Is the sound we hear being played from the recorder the same as the sound that was originally made by the tree?

Following on from this thought, how do we know that the sound you hear is an accurate interpretation of the actual soundwave? It is common knowledge that the brain frequently modifies the senses to change what it sees and hears, as seen in various illusions. Furthermore, the brain can generate sensory information without any input, known as hallucinations. You assume that your hearing is flawless and accurate, but in your mind, it is almost impossible to know for sure that the sound you heard is “real”. Taking this further leads in to the massive debate of “what is real?” and “is reality real or is it a product of our mind?”.

A more fundamental question is this: if no one was around to hear the tree fall, does it matter if it made a sound? A pragmatic philosopher might say “no”, as whether the tree made a sound or not makes no difference to your life. However, a scientist may say “yes” as the tree did fall and a soundwave was generated. Whether a person was around to observe it is irrelevant as it does not change the fact that something real occurred. Then what effect does observation have on reality? How do we know that trees make the same sound when we are not around to hear it?

This is a crude dissection of the vast number of questions the riddle offers, but it shows how such a simple thought experiment can be an effective tool to engage your critical thinking. If you do not fully understand the philosophy discussed, at least you can take away the fact that you can use the excuse of “sound is only a perception, I did not hear you, therefore what you said did not happen” when someone tells you to do something.

Posted in Science & Nature


The power of vibration is incredible. Vibration allows a microwave to heat food and causes cities to be destroyed by earthquakes. The most interesting feature of vibrations is resonance, where a vibration of certain frequency greatly amplifies the vibration of another object. Every object has a natural oscillating frequency and when another wave of the same frequency hits the object, the oscillation suddenly amplifies and resonance occurs.

The best example for resonance is a swing. If you push a person on a swing at the same frequency as the swing’s natural frequency, you can achieve a much greater height than from pushing at any other frequency. Resonance can also be used to shatter a glass with only sound, by singing a sustained note at the same frequency as the glass’ natural frequency.

Resonance is how two things combine to create an even greater force.

1 + 1 = 3