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Asked by headboywin to Anne, Carolyn, Joe, Mariana, Nick on 20 Mar 2010 in Categories: General.
Question: I've talked about this with friends before, and i have my answer, i was wondering what you guys thought... "If a tree falls in the woods and no-one is around to hear it, does it make a sound?"
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Joseph Devlin answered on 20 Mar 2010:
I’m too practical for this to have any answer but: Yes, of course it makes a sound. Sound is just a vibration in the air and a falling tree produces many different types of vibrations. There doesn’t need to be anyone present detect the vibrations for them to be there. Any other answer is solipsistic nonsense IMHO.
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Carolyn McGettigan answered on 21 Mar 2010:
Yes, it makes a sound. When an action happens in the world, a sound is made. Sound is the vibration of molecules in any medium that can carry the vibrations from that object to our ears, for example air or water. The only place where there is no sound is in a vacuum, as there is nothing around the objects to carry the vibration. You’ve heard the tagline from the Alien movies: ‘In space, no one can hear you scream’. It’s true, as space is a vacuum. So, if your tree is on Earth and it falls, it will definitely make a sound – it’s just that no one might be close enough to hear it. If the tree happens to be in a vacuum? Silence.
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Nick Bradshaw answered on 21 Mar 2010:
If a tree fell in the woods and no-one was there to here it, then it would still cause vibrations in the air. However, if there were no ears present, then nothing would detect these vibrations and no brain would interpret it as sound.
Not sure if that is a yes or a no….
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Mariana Vargas answered on 22 Mar 2010:
That’s a good one! Well…as sound is the disturbance of air molecules, then yes, the tree falling would make a sound… but of course we can’t tell if we don’t have the evidence of sound at hand after the tree falls. And of course even recording it would be cheating. This is a great question, and this kind of problem applies to a lot of experimental science, that when you’re measuring some property of a system you are interferring with it.
Comments
headboywin commented on :
i agree with Nick, surely the vibrations do not become sound until an ear detects those vibrations and translates them into sound?
Carolyn commented on :
Yay, debate!
I see what you mean, in relation to differentiating between the physical properties of energy and our perception of them. I assume you view sound as a perceptual phenomenon. However, in this case I assumed that a falling tree still makes a sound, as my basic definition of sound is as a travelling wave of vibration.
Regarding whether it has to be detected by the ear or not: A deaf person in a noisy club cannot hear the music, but s/he can feel the beat vibrating the chest and the floor. It doesn’t *sound* like anything to their ears, but they are feeling the effects of the vibration of the air molecules. So, I don’t think the vibration necessarily has to be processed via our ears to be sound.
Re the amount of sound present: You could take the viewpoint that the vibrating wave has to be detectable, by hearing and/or touch, to be a sound. I think the vibrations in the air (and the floor) from a falling tree would most definitely do that for humans. Beyond this, there are some sounds that can be perceived by other species and not us – consider bats, dogs – and some that can be heard by young people but not older adults (e.g. high frequency sounds). I don’t think we should argue that these aren’t sound just because some or all humans can’t hear them.
I suppose, after all that, we could agree that a sound is a travelling wave of vibration that is *potentially* detectable by a sense organ in a living creature. How does that sound (snarf!) for a compromise?
Cheers for the comment, and a set of great questions over the week. I’m glad to see that people are reading our responses and coming up with some very challenging ideas. As for many aspects of its processing, sound is tricky, but that’s what makes it way more interesting than light ; )
lilmissjoy commented on :
hi do you no if you should be a good scereter if you and yr best mates have fallen out affter isall over should you telll that peoson wat you Said xx thatn you joy xx
Joe commented on :
I’m with Carolyn on this. Sound is a physical phenomena. Hearing is a perceptual phenomena and therefore requires an audience.
modshamini commented on :
You could also turn this into a philosophy of science question, like what Mariana said about not being able to tell something until you record it. Since no-one has ever heard or recorded a tree falling alone in the forest, we have no evidence to suggest it makes a sound.
In science is it difficult to balance philosophical ideas like these with what we might think of as common sense?
Carolyn commented on :
I can kind of see what you mean, but it would actually be very simple for humans to put a recording device in the middle of an unpopulated (by humans) forest, travel hundreds of miles away, come back and replay the sounds it recorded, or stream the recorded material from the device to another location. I’m sure this kind of thing happens all the time in the making of wildlife documentaries.
However, I think philosophical issues can become tricky when we think about the relation between mind and brain. I believe that everything about our mental experience is described by the behaviour of our neurons, but there is a whole field of philsophy devoted to arguing this point in much more depth than I’ve ever considered.
Nick commented on :
We can even get into the real nitty gritty quantum mechanics which says that a tree neither has made a sound or hasn’t make a sound until someone checks up on it. But that just makes my head hurt…