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Yes, a magnet has both a peak magnetic field (which is what is usually quoted) and a magnetic dipole moment that is roughly proportional to diameter. The magnet
by kurthr 10y ago
Yes, a magnet has both a peak magnetic field (which is what is usually quoted) and a magnetic dipole moment that is roughly proportional to diameter. The magnetic field at a distance is proportional to the moments, but falls off proportional to the inverse cube of the distance.
So, yes if the magnet dipole were the size of Mars and it needed to be 5mT=500,000nT at 320 Mars diameters, then roughly (ignoring higher order effects) you would need an average 16kT around the surface poles, which isn't possible with current technology.
At 1 Tesla you would want to cover an area 50 times the diameter than Mars? That's pretty fanciful.
OK, either my simple calculations are bunk, or this is a truly crazy idea.
- eloff 10y agoIt's not located on/at Mars, it's located at the Lagrange point - which means much like your hand can cover entire mountains at a distance, a smaller magnetic field could shield an entire planet when positioned between mars and the sun.
- kurthr 10y agoBased on the drawing that they made the size is at least 1-2 diameters of mars (but there is no field there?). Since the diameter of Mars is ~4000mi that would >10,000km at 5mT. So with the mentioned 1-2 Tesla starting field, we end up and a cube law reducing the strength 200x at 6 times the distance, and a 1.5km moment. That would require at least 2-3km^2 of 1T magnets. Ignoring the support structure that would have a volume of ~10^10 cm^3 and weigh 100ktons, but only cost $100B on Earth at todays Samarium Cobalt pricing, if the market wasn't highly distorted. Sounds more reasonable...
- LeanderK 10y agosounds surprisingly realistic if you consider that this is a proposal to create an artificial magnetic shield for an entire planet.
- tankenmate 10y agoAlso, isn't there a shockwave effect?
- effie 10y agoYour hand does not cover entire mountains, only your eyes. The cross section of effective magnetic field has to cover the whole planet.