Re: Inertial-dampening systems

From: Timo Nieminen (timo_at_physics.uq.edu.au)
Date: 02/16/05 

Date: Thu, 17 Feb 2005 09:20:58 +1000

On Thu, 16 Feb 2005 msadkins04@yahoo.com wrote:

> Timo Nieminen wrote:
> > On Thu, 16 Feb 2005 msadkins04@yahoo.com wrote:
> > > Timo Nieminen wrote:
> > > > On Wed, 15 Feb 2005 msadkins04@yahoo.com wrote:
> > > > >
> > > > > How fast the magnetic fields change is a matter of the
> > > > > technical design employed.
> > > >
> > > > No. If the change is too rapid, the gradient force on
> > > > different parts of the passenger(s) will be different,
> > > > and the field, rather than protecting them, will rip them
> > > > apart.
> > >
> > > Wouldn't the existence and degree of gradient force depend upon the
> > > technical design employed?
> >
> > Of course. And, also of course, the existence of gradient forces is
> why
> > the system works. The magnetic force accelerating the passenger IS
> the
> > gradient force.
> >
> > So, what limits does that place on the rate of change of acceleration
> that
> > can be compensated for?
>
> If you're talking about tidal forces, and you seem to be with reference
> to the magnetic field "tearing apart" a body if switched too fast, I
> don't see that one needs a gradient force to do work: one only needs
> the frog or other body to be repelled by the magnetic field.

Read Berry & Geim. The gradient force is what repels the frog or other
body. In a spatially uniform field, there is no repulsion force.

All I'm saying is the gradient force had better not vary too quickly
across the body of the passenger. Do you really disagree with that?

> Also, I'd like to amplify something that I wrote earlier. It bears
> upon the question of induced currents, but also may be relevant to the
> gradient question:
>
> Adkins:
> "The time for the frog to be crossed at c, and the time for the wave
> front to wash over it, are the same, since the wave travels at c. The
> wavefront can be idealized as a geometric line or curve, since the
> vector bosons of the magnetic field are already idealized as
> point-particles anyway. You seem terribly confused, Nieminen. Look:
> let us say that the field strength is increased at some source at a
> distance from the frog. The entire ambient field will change but the
> first line of higher-energy vector bosons to reach the frog constitutes
>
> what I have here called the "wavefront". How long does it takes these
> particles to move, at c, over the distance of the frog's body, if it
> is, say, 2cm in length?"
>
> Now, that is one heck of a fast change in magnetic field strength where
> the frog is. So, either the theory that says that very fast changes
> should induce very large currents is wrong, or else the current is so
> brief that even a large one doesn't cause biological damage.

The example - complete with numbers - I posted earlier is a sufficient
reply to this. Go back and actually read it.

I'll stick to using the Maxwell equations, you can continue to make up
your own if you want.

> That's
> all the *more* reason why changes in static magnetic field strength
> should be made faster. Hence, there is no problem with respect to
> making fast changes in response to sudden, high-magnitude
> accelerations. And any problem with tidal forces (and I'd like to see
> that quantified -- I don't think it's relevant anyway) can be dealt
> with per above.

If, by tidal forces, you mean change in gradient force, go ahead and read
the last page of Berry & Geim. 

-- 
Timo

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