|MadSci Network: Physics|
Dear Remo, Your question, as I understand it, seems to contain two parts: 1) Is it possible to generate such a field with a living organism (like a human being), and 2) Could this be used to approximate the effects of gravity in a zero g environment. To answer the first part, a number rather unusual items have been levitated using the method you mention (or one similar to it), including live frogs and grasshoppers in magnetic fields with a strength of ~10 Tesla at the High Field Magnetic Laboratory at the University of Nijmegen: http://www.hfml.ru.nl/levitate.h tml Fortunately, there are no known adverse health effects associated with living tissue in the presence of strong electromagnetic fields. To give you an idea, most MRI machines in use in U.S. hospitals operate at between 0 – 2.0 Tesla (5000 – 20000 Gauss), although there are examples of 4 Tesla machines, and an 8 Tesla machine was recently unveiled at the Ohio State University in Columbus. Compared to the Earth’s magnetic field, which has a field strength of only 0.5 Gauss, these magnets are quite powerful. http://medicine.osu.edu/radiology/Faculty/Professors/chakeres_donald.h tm This levitation occurs because all materials, including living organisms are diamagnetic. (Paramagnetism, the mild attraction to a magnetic field, is stronger in objects with unpaired electrons.) The electrons present in the diamagnetic object align themselves anti parallel relative to the external magnetic field, creating an induced magnetic field. In the case of our frog (or your strawberry), the electrons in every molecule of its body are aligned by the external magnetic field. This results in the levitating body exerting a very small force opposite in direction to the external magnetic field, resulting in a force about 1e-5 times the strength of this external field and opposite in direction. So, it is possible to generate such a force in a living organism and it would likely not have any adverse health effects. However, there are a couple of snags which would seem to preclude its use in a spaceship. The first is that the presence of such strong powerful magnetic fields throughout a spaceship will likely wreak havoc with all of a ship’s electrical systems. Not to mention the fact that metallic objects would likely have to be removed. (Click on the link below to see the effects of a fully loaded pallet jack sucked into the bore of an MRI.) http://health.howstuffworks .com/mri2.htm Another potential problem lies in the generation of the fields themselves. As discussed by Berry and Geim (Berry MV and Geim AK, “Of flying frogs and levitrons” Eur. J. Phys. 18 (1997) 307-313), the fields used to levitate diamagnetic objects operates by creating regions of equilibrium where the forces of gravity and the induced magnetic field cancel each other out. As the authors describe, there is a shape-induced dependency of the induced magnetic moment, and levitation occurs at a point which is an energy minimum inside the solenoid possessesing spherical symmetry. This suggests that if such a field were used to ‘suspend’ an individual on the floor of the spaceship, walking around would cause one to leave the field, thus leaving the energy minimum. So, a person on the spaceship would only experience this ‘artificial gravity’ at a single point. Sincerely, Anthony
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