Scientists have figured out a way to create and cancel magnetic fields from afar.
The method involves running electric current through a special arrangement of wires to create a magnetic field that looks as if it came from another source. This illusion has real applications: Imagine a cancer drug that could be delivered directly to a tumor deep in the body by capsules made of magnetic nanoparticles. It's not possible to stick a magnet in the tumor to guide the nanoparticles on their journey, but if you could create a magnetic field from outside the body that centered right on that tumor, you could deliver the drug without an invasive procedure.
The strength of a magnetic field decreases with distance from the magnet, and a theorem proven in 1842, Earnshaw's Theorem, says that it's not possible to create a spot of maximum magnetic field strength in empty space.
Another use might be improving transcranial magnetic stimulation, which uses magnets to stimulate neurons in the brain to treat depression. Being able to control magnetic fields at a distance could improve the targeting of transcranial magnetic stimulation, so that doctors could better focus on particular regions in the human brain.
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