Me and a few friends started to argue about magnets. Of course we know there are the laws of thermodynamics that basically say you cannot generate energy from nothing.
But what of magnets? If i stick a magnet to the fridge it must be generating at least enough energy to not fall down due to gravity.
Where is this energy coming from? Should it not like run out of energy sometime?
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> it must be generating at least enough energy to not fall down
This is incorrect, in the same way that a stone doesn’t need to expend energy to stay put on the floor, or a picture doesn’t need to use energy to stay hanging on a wall.
Generally, energy is expended to *move* against a force. Though of course that principle gets difficult when thinking of eg flying objects (there is lots of air being moved around even for something hovering) or electricity (electric charges and fields are moving), but static magnetism, once it has reached a steady state, doesn’t use energy up. It’s a bit difficult to ELI5 why, but essentially all the atoms in the magnet want to point the same direction, and as a result make a magnetic field that also influences atoms in the fridge to point in the same direction, which in turn creates its own magnetic field in the magnet. This interaction pulls the magnet and the fridge together, such that the friction between them is higher than the weight of the magnet and it stays in place. The “atoms lining up one way” is an elastic process, kind of like they’re all little springs being stretched or twisted a little bit, so they can stay stretched quite happily and spring back together after the magnet and fridge are separated.
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