Hanon:

I don't know why they got those strange results when doing the probing with the Hall effect sensor.  However, the Hall sensor will have it's own measurement limits.  Was this discussed in the books?  Also, the Hall sensor needs DC current to function and this may disturb the ambient magnetic field that you are trying to measure when it is not very strong.  I never used a Hall sensor so I am just speculating.  The possibility I am looking at is the Hall sensor's measurements were unreliable were the magnetic field is weakest, along the center of the outside of the magnet.

Just to talk nasty for a second, there exists the possibility that the whole Howard Johnson/Davis and Rawls business is a con.

I tried to look up a magnetic field direction sensor consisting of a tiny magnet inside a set of tiny gimbals but I couldn't find one.  I bet you they exist though.

As long as the iron filings are lightly sprinkled they will not disturb the magnetic field of the magnet in any significant way.

Here is the explanation for the swirling bubbles:

http://www.youtube.com/watch?v=5Fnq8TGbTfE

The "Magnet Flipper" guy made that clip and claimed the "swirling bubbles" were a new discovery or something like that when in fact he had no clue what he was looking at.

MileHigh

QuoteI tried to look up a magnetic field direction sensor consisting of a tiny magnet
inside a set of tiny gimbals but I couldn't find one.  I bet you they exist
though.

Yep.

http://www.indigo.com/magnets/magnaprobes/

And they tell you about the same story as a flashlight tells you about photon packets.

QuoteThe iron dust becomes a magnet when exposed to a magnetic field. It is like
trying to measure the weight of an object with a scale whose internal parts
become more weighted when a object is put over it.

Hanon, well put. 

Our current understanding of this reality is rather like an infant's view of the world from inside it's mother's womb.  Man has spent so much time, so much effort, for such tentative steps toward greater understanding.....When so many 'shortcuts' have been designed all around, within and without us.

TS

Why is it that as long as the iron filings are lightly sprinkled they will not disturb the magnetic field of the magnet in any significant way?

QuoteWhy is it that as long as the iron filings are lightly sprinkled they will not
disturb the magnetic field of the magnet in any significant way?

Depends on one's subjective understanding of the relevance of the term, significant.

http://www.youtube.com/watch?v=EMLPJqeW78Q

So, when and if one is able to peer into the smallest of the small, perhaps we discover how irrelevant our observations of what 'big' and 'small' really are.

Your question is tantamount to asking, "Why is it that when small gravitic dipoles, such as satellites and micro-meteoroids are lightly sprinkled in earth orbit, they will not disturb earth's gravity field in any significant way?"

TS

TS:

Thanks for the link to the gimbal sensors.  Very cool, I think every experimenter should have one.  You could check out your field from your big Tesla coil if it was sensitive enough.  Of course you could always push extra current through your coil to make the measurement.  Also, very useful to check the coupling between magnets and generator coils.

The ones you linked to looked kind of cheap through, not lab grade.  I bet you there are old lab grade ones from the 1960s that are beautiful.

Not significant would be that the field lines, if they are disturbed, would be displaced by less than 0.5% of their normal distance from the center of the magnet.

QuoteWhy is it that when small gravitic dipoles, such as satellites and micro-meteoroids are lightly sprinkled in earth orbit, they will not disturb earth's gravity field in any significant way.

It is a good analogy.  Can someone answer the question though....

MileHigh