The bird who lived on the tree heard a smashing sound!

"If you're driving down the street in your motorboat and your wings fall off, how many pancakes does it take to cover a doghouse?"
Lets see:
area_of_doghouse / average_area_of_pancake
or:
area_of_doghouse / (average_area_of_pancake - pancake_overlap)
Am I getting close?
As to the checken/egg/road problem, I have the distinct impression that the chicken got left muttering "WTF???" to himself...

"No one to hear it" means bird was deaf or wasn't there.

Modern science could prove the sound waves and or pressure waves were there, just lack of a human ear to actually interpret the waves. But if that is what causes sound to get interpreted, if someone is there or not, the evidence is clear that it makes a sound of some kind.

But it exists in a near-vacuum. As you transition to a perfect vacuum, what happens to the equations?

Here's on article that plots the speed of sound on Earth up to 400,000 feet. The trend is to increase with altitude.
http://www.aerospaceweb.org/question...re/q0249.shtml

Sure it does. Acoustic (longitudinal) plasma waves.

OK, let's consider the color of light. Until we had humans--with eyes that respond from 400-700 nanometers--there was no definition of--eg--"yellow". Our definition of color is based on how our eye responds to specific wavelengths.

For example, with the right power settings, we cannot see the difference between monochromatic radiation at 550 nm and TWO sources on either side of 550. A spectrometer will see the difference easily.

The color is not "yellow" unless there is a human there to see it.

Color and sound are totally different. What does the color yellow have to do with sound?

Sound is the human perception of the properties of pressure waves
Color is the human perception of the properties of electromagnetic waves

In both cases, the waves have to fall within our range of perception.

In France there is no yellow, but we have something similar called "jaune". I hear the Italians can't see yellow either but have something called "giallo".

Now for the other bits:

Chicken vs. egg: Easy - dinosaurs had eggs and came long before the chicken, so the egg was first (unless you're a creationist, then the chicken was first because god created the animals, not the eggs).

A tree falling in the forest? The tree will definitely compress the air as it falls (and rarify the air behind it) so the vibrations that we'd interpret as a whooshing sound will be there. The wood must also splinter, producing what would be interpreted as a cracking sound, and the tree may hit other trees or hit the ground, producing more vibrations. So the answer is "yes, the tree will produce a sound" unless, of course, you claim you did not have sex with Monica Lewinsky in which case "I repeat: that tree did not make a sound when it fell".

I think that purpose of the question wasn't scientific, more like "how can you make sure that something happens, when there is no one to notice this?" so the answer about sound waves wasn't "right", I think. But, I think, the question was asking "for fun", so the answer isn't really important. Another questions like this include "what color is chameleon on the mirror" (you can easily find the answer to this one).

Chicken/egg question is a neither really - although dinosaurs had eggs, they weren't chickens. Alternatively, you could say the chicken evolved the egg on the grounds that it helped protect their young.

In response to the original topic (havent read the posts)

If anything falls and impacts something else it creates residual vibrations which are transmitted through the air assuming there is an atmosphere (this isnt a tree in space or on the moon). So according to physics than yes the tree does make a sound.

However there is another factor to consider which is Schrodingers cat. If no one can view the cat in the box then it may or may not be there. So therefore if no one can sense the sound of the tree it may or may not make a sound and unless you remove the box or enter earshot of the tree the truth is that you will never know!

But the question was about a chicken and an egg, not a chicken and a chicken egg. The chicken would probably have evolved from some other animal which also laid eggs. I'm no paleontologist though so I don't know anything about the evolution of the chicken; I haven't heard of any evidence of a chicken ancestor which gave birth to live chicks which did not develop via an egg. Many animals (including humans) reproduce via eggs (even if they don't 'lay' eggs like a chicken), but some animals (like many types of worms) can reproduce from segments.

Quick - someone ask me about the 'sound of one hand clapping' - I feel like slapping someone for fun.

I don't understand your point. Plasma is not a vacuum.