Ask Blue_Nose

Another question pulled from the AskBN vault:

I do have a question, a real bastard of one. If a tree falls in the woods, does it make a sound?

I'm going to assume by this you're referring to the tree that falls in the forest when nobody is present to witness it.

Philosophy types like to haggle over this issue as it relates to reality vs perception, or just claim the whole thing is "unanswerable", but luckily for my readers, metaphysics is an area in which I'm particularly an expert.

To start off, we'll attack this from a purely scientific/logical viewpoint, and then we can get into some of the more abstract ideas.

Logically, the question is flawed - it makes the assumption that trees make sound at all. What's really going on when the tree falls?

The sudden failure of the wood creates a change in pressure in the air around it, just like ripples on the surface of a pond, except in three dimensions. These pressure waves spread out through the air, bouncing off any solid objects in their path, including any eardrums that happen to be in the area. Without concerning ourselves with the detailed biology crap, the eardrum vibrates due to the pressure waves and converts this to a signal which is sent to our brain.

Note that in that entire paragraph, I didn't mention the word "sound", yet it's a fairly detailed and accurate description of the event. So where does "sound" fit in? Some like to think it's at the tree breaking, others think it's at the eardrum, and others still believe it's at the brain. Since "sound" doesn't have any inherent characteristics that aren't explained by other processes, our concept of what "sound" means is vague and arbitrary.

Let's start narrowing our options down - first, the idea that the tree produces a sound: since we know that the tree snapping is creating pressure waves, and we know that pressure waves don't necessarily create sound (I can wave my hand in the air without making a sound), we can eliminate that option.

Next, the argument that sound "happens" in the eardrum - since all the eardrum is doing is vibrating from the waves that hit it, we can't really call that sound, either. A boat rocking in choppy water isn't "hearing" the waves, and the rock sitting next to the tree that fell didn't "hear" it fall, even though the pressure waves undoubtedly hit it and caused it to vibrate.

So we've narrowed it down to inside an observer's brain - not bad. We're not done yet, though, and this is where it gets a little more sketchy.

I just stopped typing for a few seconds to listen to what was going on around me - other than the stereo ("1000 Umbrellas" by The Format), I heard a bird chirping outside, and a truck starting up. I hadn't notice the bird until then, but it's safe to say that it's probably been chirping away and I was just focused on typing. Let's ignore the fact that the bird obviously heard itself - even though my eardrums vibrated and the signal was sent to my brain, was there actually any "sound" if I didn't notice it? If I hadn't stopped and listened for it, and someone asked me tomorrow if I'd heard any birds chirping today, I'd have said no, even though it was right outside my window.

So, can we logically say that something occured that we didn't notice? Considering these questions would lead one to accept that in order for a "sound" to exist, it has to be not only observed, but acknowledged. Some people are uncomfortable with this idea, because they think it implies that reality exists only in our minds, but that's not the case - all it says is that our perception of the world is limited to our observations. We have no idea if any tree falls down unless we see or hear them, but that doesn't stop them from falling when our backs are turned.

That's another discussion, though, and I think we have enough to answer the original question - let's end with something a little less cerebral: