Quantum physics: Logical example?

Question

Is this an example of quantum physics?

"If a tree falls in the forest and no one is around to hear it, does it make a sound?"

I believe that this is an example of the rule that states "an object only collapses to a definate state when it is measured".

Any ideas?

Answer 1

Although I ABHOR science today (it is quite arrogant and thus "plateaued"), this philosophical question is similar to Schrodinger's Cat.

Let |1> represent the tree making a sound, and |2> represent the tree not making a sound, then X, the function describing the state of the [sound of the] tree is

X = a|1> + b|2>, with a^2 + b^2 = 1 (basic quantum).

So, while it is true that quantum mechanically the sound the tree makes "is" when the state is measured, one can say that we already know (based on physics) that trees hitting the ground will give off some thermal and radio energy (i.e. will make a sound). We can do these calculations based on mass, velocity, etc...

Philosophy is just what it is, philosophy. One could easily say that our perception of "sound" is based on the fact that we have cochlear sensors that "pick up" sound, and thus we can observe it. Trees could philosophically give off "ANKWAR" radiation, which only, say, lifeforms from the planet "Quantmar" can detect... does that mean trees dont make an... "ANKWAR"?

Philosophy is a great introduction and doorway into hard natural sciences. This question is a great one posed by many scientists and philosophers alike.

Answer 2

It's taking an analogy too far.  In quantum physics, a physcial variable doesn't have a definite value until it's actually measured.  But that only applies to object in a quantum superposition state---which a tree falling in a forest is not.  Yes, in theory a tree could be in a quantum superposition state also, but in practice it's almost impossible to prepare a whole tree to be in such a quantum state for any length of time.  Decoherence theory explains why.  So, when a tree falls in a forest, it makes a loud crashing noise, regardless if there is anything around to "hear" it.

Answer 3

At first glance it might appear as though this is an example of quantum physics, of the same type thought experiment as Schroedinger's cat, but it's not, for one very simple reason. In Scroedinger's cat the cat can be either alive or dead, and we don't know which until we open the box and look. But in the example of the tree falling in the forest there is no such ambiguity, because the statement begins by stating unequivicably that the tree fell. The tree is not stuck in some nether world between standing and falling. It has definitely fallen. Therefore, it made a sound.

Answer 4

Everyone so far is right.  Let me add that the length of time a superpositions exists is directly related to how well the system is coupled to the environment.  A tree in a forest is extremely well coupled to its environment (energy passes freely between tree and the rest of the universe) so any superposition involving a tree would decohere extremely fast (there would be no words for describing how fast it would decohere, it would be so fast).  So a tree superposition would not last long enough for a tree to fall (it would not last long enough for anything to happen).  So quantum mechanics tells us that that is specifically not quantum physics.