Re: [Phys-l] feeling gravity, or not

[Bernard Cleyet <bernardcleyet@redshift.com>]

I just received the below:  [including an attachment.]

The springs and blocks are an addition to Alph., M. E., et alia's 
description.

Why Do We Feel Weightless in Free Fall?

THE PHYSICS TEACHER ? Vol. 44, April 2006

[Being able to attach would be so useful!]



bc, who thinks one is unlikely to ever feel gravity and survive. 
[courtesy of JD]

John Gastineau wrote:

> Bernard--
>
> Not sure if this has come up in the discussion (I think i'm missing 
> some emails), but note the attached paper from TPT.
>
> There's a song lyric that runs "I've been falling so long, it feel 
> like gravity's gone" in a tune by a band called the Drive By Truckers, 
> which makes me think of this paper and discussion. Popular music gets 
> the physics right!
>
> JG
>
> John Gastineau
> Staff Scientist
> Vernier Software & Technology
>
> 888 837 6437 voice
> jgastineau@vernier.com
>
>
>
> Bernard Cleyet wrote:
>
> >    
cut

> > bc
> >
> > John Denker wrote:
> >
> >  
> >
> > > On 10/29/2006 07:46 AM, carmelo@pacific.net.sg wrote:
> > >
> > >
> > >
> > >    
> > >
> > > > In a sense, we can't tell whether we are feeling the gravity or the effect of acceleration, or a
> > > > mixture of both. We could not even feel the effect of acceleration due to the rapid expansion of
> > > > the universe, if there is any. 
> > > >   
> > > >
> > > >      
> > > Does that mean to say gravity, or uniform gravity?
> > > There's a big difference between uniform acceleration and
> > > acceleration in general.
> > >
> > >
> > >
> > >    
> > >
> > > > We can only deduce the feeling if we can look out of the so-called
> > > > "window"...
> > > >   
> > > >
> > > >      
> > > That depends.  We don't need a window in the wall if the
> > > wall is already far-enough away.
> > >
> > > Whether we can feel gravity depends on three things
> > > -- the degree of inhomogeneity
> > > -- the size-scale of our measurements
> > > -- the sensitivity of our measurements
> > >
> > > It's like a term in a Fourier series:  f' delta(x).
> > > Without the f', this term is zero.
> > > Without the delta(x), this term is zero.
> > > If this term is nonzero, we must ask whether it is big enough
> > > to be significant as determined by the sensitivity of our
> > > measurements.
> > >
> > > f' goes to zero in the /limit/ of a uniform field, but this
> > > limit is never really achieved in practice.
> > > delta(x) goes to zero in the /limit/ of a very very local
> > > measurement, but this limit is never really achieved in
> > > practice.
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> > >
> > >
> > >
> > >
> > >    
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