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Thread: Focused magnetism?

  1. #1
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    Focused magnetism?

    Given that light and magnetism both arise from the same fundamental force, would it be possible to build a device that is to a magnet what a laser is to an ordinary lamp?
    I.e. where we could focus the repelling or attracting force in a thin beam rather than having it spread out in all directions.
    A repelling beam could be useful when launching a spacecraft.

  2. #2
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    Code:
    →   →
    ∇ ∙ B = 0
    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  3. #3
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    I'm afraid those arrows flew over my head...

    Do you mean "the resulting force would be zero because <something>" ?

  4. #4
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    Maybe this helps.

  5. #5
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    drhex,
    The previous answers are a bit unfair on a junior member of this site, who may be ajunior member of the human race for all we know. Do tell!

    I will be rapidly overtaken by those who know far more about this, but have you compared the different natures of light and its photons with that of a magnetic field?
    Photons travel across the Universe; a magnetic field is static, unless disturbed by something.

    Certainly magnetic fileds can be focussed, by confining the field into a smaller and smaller space to produce ever increasing strengths of field.
    For instance, in medicine, Magnetic Resonance Imaging may use a field measured in tens of Teslas, when the Earth's field in microT.
    Your old cathode ray tube TV set used a magnetic field to focus and scan an electron beam on the screen, and of course the LHC uses focussed magnetic fields to keep the Hadrons in the pipe.

    So experts, answer the guy, please, don't blind him with science.

    John

  6. #6
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    Quote Originally Posted by JohnD View Post
    So experts, answer the guy, please, don't blind him with science.

    John
    I agree with you. I´m not an expert, but the link I provided is pretty friendly.

  7. #7
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    My reply was intended to be ironic (ferrous?) humor. It is, to the
    best of my knowledge, a complete and correct answer to your
    question. But obviously it means nothing to a person who dosen't
    already know what it means! It is ironic because generally other
    people provide pithy, mathematical explanations that are mostly
    incomprehensible, while I provide explanations that are easily
    understood but not supported by documentation, and so are of
    questionable veracity. In this case, I saw a good opportunity to
    turn things around. I knew that my mathematical answer would
    be recognized by others here and explained.

    Although I'm not sure the article Argos linked does that, so I'll
    go back into my usual mode and try to explain that little formula
    which equals zero.

    The formula is a representation of the second of Maxwell's four
    equations which together describe the behavior of electromagnetism.
    In essence, it says that the flux lines of a magnetic field always
    form closed loops. As a result, there cannot be such a thing as a
    beam of magnetism. The zero in the equation means that every
    flux line that you might trace going out of a magnet eventually
    comes back into the magnet.

    Now you want to know what a "flux line" is. Oh dear.

    I'd say it is sort of like an elevation line on a topographic map,
    representing a location where the magnetic field has a particular
    quality. Like an elevation line, its location is purely the result of
    convention -- it isn't a physical thing. It is an arbitrarily-located
    curve along which the magnetic field could be measured and a
    particular quality of the field would be found to be constant along
    that curve.

    I hope this explanation prompts someone to provide a better one,
    just as I intended with my first reply.

    -- Jeff, in Minneapolis
    http://www.FreeMars.org/jeff/

    "I find astronomy very interesting, but I wouldn't if I thought we
    were just going to sit here and look." -- "Van Rijn"

    "The other planets? Well, they just happen to be there, but the
    point of rockets is to explore them!" -- Kai Yeves

  8. #8
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    A flux line, or field line, or force line, is just the way to visualize a line of measurement where a magnetic field has a certain energy level (see here for more). But the part you need to know is, no, it can't form a laser-like beam; You can only stretch the field so far.
    I'm a cynical optimist. I think the only way out is through, but once we get through it'll be better. Very different, but better. Howard Tayler

    It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change. Charles Darwin

    Any technology distinguishable from magic is insufficiently advanced. Gregory Benford

    Power, Lord Acton says, corrupts. Not always. What power always does is reveal. Robert A. Caro

  9. #9
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    Electromagnetism cannong be focused to a point distant from it's origen due to the way magnetism works.

    However, it can be tightly focused within the generating mechanism to achieve extraordinarily high magnetic fluxes, on the order of 10 to 20 Teslas. One such device is the Bitter electromagnet.

    The Bitter device is a constant field electromagnet. Pulsed devices can generate upwards of 90 T, and exploding electromagnetics, which use an explosive device to collapse (implode) a pulsed electromagnet as it's activated, which compresses the magnetic field to around 1,000 T.

  10. #10
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    Well, if it was possible to do a magnet-laser I suppose someone would have built it already.

  11. #11
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    drhex,
    Don't be down hearted!
    What no one has mentioned is the railgun, that uses focussed magnetic fields to push a packet along a rail until it reaches an enormous velocity, potentially escape velocity.
    Despite the many agressive applications you will find on the 'Net, it has definite non-warfare uses, in theory at least, as a means of launching packets of inert or possibly human cargo, especially from low gravity wells and in the abscence of atmosphere. The Moon has been seriously studied.

    John

  12. #12
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    Quote Originally Posted by drhex View Post
    Well, if it was possible to do a magnet-laser I suppose someone would have built it already.
    That's not a good thing to assume. Often developments and inventions in one area will enable things not previously feasible in another. I doubt if there's a closed book in any area of invention.
    "There are powers in this universe beyond anything you know. There is much you have to learn. Go to your homes. Go and give thought to the mysteries of the universe. I will leave you now, in peace." --Galaxy Being

  13. #13
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    well, the earth produces a magnetic tail that is shaped by the solar winds.
    this "magnetotail" can extend great distances away from the originating planet. Earth's magnetic tail extends at least 200 Earth radii away from the sun.
    this "tail's" structure is dynamic and changes all of the time. sometimes it can actually break apart and parts of the magnetic tail will bubble off in the form of something called a "plasmoid" which is a coherent structure made of plasma and magnetic field lines.


    so in theory, one could form a directed magnetic field utulizing a plasma..

    here is an outline of the work in the field (lame pun intended)..

    "Magnetic guide field generation in collisionless current sheets"

    W. Baumjohann1, R. Nakamura1, and R. A. Treumann2,*
    1Space Research Institute, Austrian Academy of Sciences, Graz, Austria
    2Department of Geophysics and Environmental Sciences, Munich University, Munich, Germany
    *present address: International Space Science Institute, Bern, Switzerland
    Received: 30 December 2009 – Revised: 19 February 2010 – Accepted: 9 March 2010 – Published: 16 March 2010

    http://www.ann-geophys.net/28/789/20...8-789-2010.pdf

  14. #14
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    Quote Originally Posted by drhex View Post
    Well, if it was possible to do a magnet-laser I suppose someone would have built it already.

    did someone say that about the cell phone 30 years ago?
    or the laser 100 years ago?
    or landing a man on the moon 50 years ago?

  15. #15
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    Quote Originally Posted by JohnD View Post
    drhex,
    Don't be down hearted!
    What no one has mentioned is the railgun, that uses focussed magnetic fields to push a packet along a rail until it reaches an enormous velocity, potentially escape velocity.
    Despite the many agressive applications you will find on the 'Net, it has definite non-warfare uses, in theory at least, as a means of launching packets of inert or possibly human cargo, especially from low gravity wells and in the abscence of atmosphere. The Moon has been seriously studied.

    John
    A railgun would not be too feasible for human launches-- unless you like being flattened into a smear of jelly. The acceleration would be immediate, immense and all at once. But a long coilgun could do the job with relatively little G strain on our fragile bods, building up speed relatively slowly until launch.
    I'm a cynical optimist. I think the only way out is through, but once we get through it'll be better. Very different, but better. Howard Tayler

    It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change. Charles Darwin

    Any technology distinguishable from magic is insufficiently advanced. Gregory Benford

    Power, Lord Acton says, corrupts. Not always. What power always does is reveal. Robert A. Caro

  16. #16
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    Quote Originally Posted by JohnD View Post
    What no one has mentioned is the railgun, that uses focussed magnetic fields to push a packet along a rail until it reaches an enormous velocity, potentially escape velocity.
    Railguns don't use "focused" magnetic fields any more than any other electromechanical device does. They don't have much relevance to the topic, which would be why nobody else has mentioned them. And other types of electromagnetic mass drivers have characteristics better suited to the applications you mention, being far more scalable to larger payloads and lower, more controlled accelerations over longer distances...similar systems being under current development to replace steam catapults on aircraft carriers. (look up EMALS)

    Materials with high magnetic permeability can be used to "focus" magnetic fields in the sense of concentrating them into a smaller volume and changing their shape. A steel paperclip stuck to a magnet will temporarily magnetize, carrying enough magnetism to attract other paperclips with enough force to lift them against gravity at a distance where the actual magnet would not be able to do so. There's no beams of magnetism, no analogy to refraction...it has more similarities to conduction of electrical current than to focusing of light.

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