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What is the speed of two magnets during the congruent moment of their attraction?

Theoretically, could a large enough magnet attract a significantly smaller magnet at near the speed of light? In other words, suppose you had a magnet the size of a planet and another the size of a football, how fast would they attract?

Would the speed increase given the colossal size difference?

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  • $\begingroup$ Making one of the magnets larger doesn't give you more attraction. It merely gives you more torque. What attracts magnets to each other are the gradients of the magnetic fields, i.e. one has to make the field as inhomogeneous as possible. But even with the most advanced materials and the most advanced shapes the resulting forces will be disappointingly small. The best designs to accelerate masses with magnets are the electromagnetic guns aka rail guns. For ion acceleration induction accelerators can be used to get close to the speed of light with large beam current. $\endgroup$
    – CuriousOne
    Dec 19, 2014 at 6:38
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    $\begingroup$ I'm not sure what you mean by "congruent." However, there's more to magnetism than permanent dipoles; look up "railgun." $\endgroup$
    – rob
    Dec 19, 2014 at 6:38
  • $\begingroup$ @CuriousOne Essentially, what I am asking is how much of a speed boost are we talking here? If magnet A were the size of a planet and B were the size of a football, would standing in between the trajectory of these two entities be a bad idea? Would the attraction obliterate anything caught within the path of entity B?(Which is smaller and thusly, going to be the one who shoots across space to meet the larger entity A) $\endgroup$
    – Krythic
    Dec 19, 2014 at 6:59
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    $\begingroup$ If one magnet were the size of the Earth, the other magnet would hardly move, at all. Like I said, the force is proportional to the gradient of the field, not the size of the field. Since the gradient of a large magnet is much smaller than that of a small magnet, the result would be extremely disappointing. $\endgroup$
    – CuriousOne
    Dec 19, 2014 at 7:03
  • $\begingroup$ Related...physics.stackexchange.com/questions/67826/… $\endgroup$
    – Paul
    Dec 19, 2014 at 12:43

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