Re: World's noise

[John Clement <clement@HAL-PC.ORG>]

This is an excellent teaching opportunity.  I think the student has observed
objects that rotate and notice that there is a noise associated with the
rotation.  Perhaps you could bring in several objects that rotate and ask
when they make noise, and when they make none.  Bring in a rotary grater,
toy cars with wheels, and something that has very little friction, so the
noise is extremely small.  Get the students to see if they can come up with
an idea of when they make noise.  Try to guide them, and not tell them.
Once they realize that friction or resistance to rotating is small when the
noise is small, you can ask why you can not hear the noise of the Earth
turning.  They should be able to say the friction (or some such words) is
small.

Once they come to this realization, show them an electric fan, and ask why
it makes the shhhh ing noise.  They should realize that it is the air being
pushed.  You might also have to use a simple Chinese fan also.  At that
point they might be able to say, that the Earth is turning in space where
there is no air.  The fact that space has no (or essentially no) air is an
idea that many students do not understand.  Similarly they will tell you
there is air on the Moon and/or there is no gravity on the moon.

John M. Clement
Houston, TX

> -----Original Message-----
> From: phys-l@lists.nau.edu: Forum for Physics Educators
> [mailto:PHYS-L@lists.nau.edu]On Behalf Of Muhsin Ogretme
> Sent: Saturday, September 08, 2001 9:20 AM
> To: PHYS-L@lists.nau.edu
> Subject: Re: World's noise
>
>
> > Well, there are several ideas in there;  let's take them separately.
> >
> > A1) If we take the word "while" literally, then the answer is that the
> > world does make a big noise !while! rotating, and we most certainly can
> > hear it.  I can hear waves crashing on the seashore.  I can hear wind
> > whistling through the trees.  I can hear animal activity and human
> > activity.  Et cetera.  All this goes on !while! the world is rotating.
>
> Yes, :-) . My student meant did the earth create noise just because of
> its rotation, as you guessed in A2. It was a cause-effect relation.
> Cause: The earth rotates, effect: noise? He actually was looking for if
> there was such a cause and effect relation. Do you think that all the
> sounds (except the ones created by human activities such as speaking,
> concerts etc.) like the crashing waves on the earth has a symetrical
> relation with the rotation?