Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?




--
On the free trade agreement between Australia and the US there is a big
difference between the heading of the agreement and what the body
states.

Observations of Bernard - No 47

Dear Bernardz:

"Bernardz" wrote in message
news:MPG.1aa5d9133162c2f0989931@news...
Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?

Remember, nothing is ever seen to pass the event horizon. So your
"detector" would point closer and closer to the event horizon. Also, since
magnets are motion-of-charge based, the field strength of the magnet would
appear to decrease as it got closer to the horizon.

David A. Smith

Bernardz wrote:
Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?


Consider the tidal forces outside the event horizon. You need
first to understand all that's happening outside.

Bernardz:
Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?


That's a good question assuming you meant why _couldn't_ you follow the
path of the magnet. Better yet, why couldn't you determine its orientation
as it fell toward the sigularity. That doesn't get ruled out so easily,
since the magnet does have a dipole moment and there's no reason to assume
that there is anything special about the horizon that would destroy the
alignment of the dipoles in the magnet.

Intuitively, I would say that you will measure the dipole moment
corresponding to the orientation of the magnet as it crossed the horizon
with the dipole moment becoming smaller and smaller until it vanished.
I would draw it schematically like this:

A magnet has a current which is just the loop around the dipole moment.
Assume the magnetic field points into the page,

J -
+------ + Now, as the magnet crosses the horizon, the field
| xxxxxx | due to the dipoles in the magnet will become
| xxxxxx | smaller and smaller as the horizon "truncates"
| xxxxxx | the "current loop". You get the same result with
+ ------+ any orientation, just in a different way.

-------- horizon ----

If a black hole behaves like a superconductor, then the meissner
effect would presumably result in the field appearing over the surface,
independent of what happens to the magnet. This seems somewhat reasonable,
since the field of the magnet can never reach the horizon. Whether the
hole retains any magnetization, I don't know.

This isn't totally satisfactory though. The dipole could be a single
electron, which means the hole picks up a charge and a spin of 1/2,
which should give the black hole a real dipole moment (extremely small
by comparison, to any other effects, to be sure, but this is a
hypothetical question).

That might be argued away by "statistical fluctuations" somehow, but I
don't know how to do that and justify it. One might, for instance, argue
that the magnet would be heated well beyond the curie temperature, but
that seems a bit of a stretch. So, I really can't give you a definitive
answer. Perhaps someone else can.

Bill Vajk:


Bernardz wrote:
Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?


Consider the tidal forces outside the event horizon. You need
first to understand all that's happening outside.

The tidal forces can be as small as one wishes to connsider by
assuming a large enough black hole mass. In principle, the gravitational
field at the horizon could be 1 g (or less).

Bernardz wrote:

Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?



Since you would never observe the magnet to cross the event horizonin the
first place, what is the point of your question?

John Anderson

Bernardz wrote:

Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?

--
On the free trade agreement between Australia and the US there is a big
difference between the heading of the agreement and what the body
states.

Observations of Bernard - No 47

In article ,
says...
Bernardz:
Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?


That's a good question assuming you meant why _couldn't_ you follow the
path of the magnet.

Yes I did.

Better yet, why couldn't you determine its orientation
as it fell toward the sigularity. That doesn't get ruled out so easily,
since the magnet does have a dipole moment and there's no reason to assume
that there is anything special about the horizon that would destroy the
alignment of the dipoles in the magnet.

Intuitively, I would say that you will measure the dipole moment
corresponding to the orientation of the magnet as it crossed the horizon
with the dipole moment becoming smaller and smaller until it vanished.
I would draw it schematically like this:

A magnet has a current which is just the loop around the dipole moment.
Assume the magnetic field points into the page,

J -
+------ + Now, as the magnet crosses the horizon, the field
| xxxxxx | due to the dipoles in the magnet will become
| xxxxxx | smaller and smaller as the horizon "truncates"
| xxxxxx | the "current loop". You get the same result with
+ ------+ any orientation, just in a different way.

-------- horizon ----

If a black hole behaves like a superconductor, then the meissner
effect would presumably result in the field appearing over the surface,
independent of what happens to the magnet. This seems somewhat reasonable,
since the field of the magnet can never reach the horizon. Whether the
hole retains any magnetization, I don't know.

This isn't totally satisfactory though. The dipole could be a single
electron, which means the hole picks up a charge and a spin of 1/2,
which should give the black hole a real dipole moment (extremely small
by comparison, to any other effects, to be sure, but this is a
hypothetical question).

That might be argued away by "statistical fluctuations" somehow, but I
don't know how to do that and justify it. One might, for instance, argue
that the magnet would be heated well beyond the curie temperature, but
that seems a bit of a stretch. So, I really can't give you a definitive
answer. Perhaps someone else can.


Thanks for what you supplied.





--
On the free trade agreement between Australia and the US there is a big
difference between the heading of the agreement and what the body
states.

Observations of Bernard - No 47

In article Q7J_b.556$h23.53@fed1read06, "N:dlzc D:aol T:com \(dlzc\)"
N: dlzc1 D:cox says...
Dear Bernardz:

"Bernardz" wrote in message
news:MPG.1aa5d9133162c2f0989931@news...
Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?

Remember, nothing is ever seen to pass the event horizon. So your
"detector" would point closer and closer to the event horizon. Also, since
magnets are motion-of-charge based, the field strength of the magnet would
appear to decrease as it got closer to the horizon.

David A. Smith




I will make it easy for you. Say inside the black hole, a magnet went
close to the event horizon. Why could we not detect this?



--
On the free trade agreement between Australia and the US there is a big
difference between the heading of the agreement and what the body
states.

Observations of Bernard - No 47

In article ,
says...


Bernardz wrote:

Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?



Since you would never observe the magnet to cross the event horizonin the
first place, what is the point of your question?

Irrelevant. Say the magnet was already be in the black hole right up
close to the event horizon. We should not be able to detect this
movement but I cannot see why we could not.


.................(Detector)..................
++++++++++++++++++++++++++++++++++++++++++++++++++ ++++ event horizon
.................---(magnet)----........... magnet moving






John Anderson

Bernardz wrote:

Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?

--
On the free trade agreement between Australia and the US there is a big
difference between the heading of the agreement and what the body
states.

Observations of Bernard - No 47







--
On the free trade agreement between Australia and the US there is a big
difference between the heading of the agreement and what the body
states.

Observations of Bernard - No 47

"Bernardz" wrote in message
news:MPG.1aa5d9133162c2f0989931@news...
Assuming that near a black hole I had a very powerful magnetic position
detector.

If I dropped into a black hole a magnet. Why could I follow the path of
the magnet, once it passed the event horizon?

Once inside the black hole the magnetic fields would not be detectable. This
sounds something like the "no-hair conjecture" - Consider a star, which has
a magnetic field, which is imploding into a black hole. The gravitational
field "forces" the field lines down into the hole. When the hole is formed
the magnetic field lines are totally within the event horizon - Or so the
black hole gurus say! :-)

Pmb