Why Do Magnets Attract, at a Fundamental Level? Why? Why? Why?

Try the best online learning platform FREE for 30 days: http://brilliant.org/arvinash - Get a 20% discount on the annual premium subscription if you subscribe! FURTHER STUDY Quantum ElectroDynamics (QED)    • How QED Unites Relativity, Quantum Mechani...   Quantum Field Theory (QFT)    • Quantum Fields: The Most Beautiful Theory ...   TALK TO ARVIN ON PATREON   / arvinash   CHAPTERS 0:00 What's the magnetic force? 0:46 Going deep into a magnet 1:33 Quantum property of spin 2:35 How does a material become a magnet 3:28 Standard explanation for magnetism 4:27 Quantum ElectroDynamics - virtual photons 7:26 Down the Rabbit Hole of Quantum Mechanics 8:52 Pauli Exclusion Principle 10:08 Why do only SOME material become magnetic 11:23 Exchange interactions 12:40 Wavefunction interference at the heart of magnetism 15:00 Summarization of everything SUMMARY Why do magnets attract? What is the mechanism? What's actually happening behind the scenes at the atomic and quantum level? Magnets are made of atoms, and atoms are composed of a positively charged nucleus surrounded by negatively charged electrons. Electrons are tiny charged particles that orbit the nucleus, and have a quantum property called spin. it is a type of intrinsic angular momentum . The spin creates a tiny magnetic field. Most materials have electrons spinning randomly, so their magnetic fields cancel each other out, resulting in no overall magnetism. But in certain "ferromagnetic" materials, like iron, cobalt, or nickel, electrons align their spins with each other due to quantum mechanical interactions. When synchronized, their tiny magnetic fields combine, becoming stronger. Groups of aligned electrons create microscopic regions called 'magnetic domains.' where all electron spins point in the same direction, creating a strong local magnetic field. These domains themselves are randomly oriented, cancelling each other out, so the material overall is not magnetic. But when you magnetize a piece of iron by exposing it to another magnet or electric current, you force most of these domains to align in the same direction, turning the material now into a magnet. So that’s how a magnet is created! Why do magnets attract? The standard classical explanation is that Magnets interact through their magnetic fields. When opposite poles of two magnets get close, their field lines naturally flow from one magnet into the other, creating a a stable, lower-energy state. Nature loves to lower energy, so this configuration pulls the magnets together. Conversely, when two similar poles face each other, their field lines clash— creating tension or pressure that drives them apart. Magnetism is explained through quantum electrodynamics, or QED. QED is the theory that describes the electromagnetic force, and says this force results from the exchange of virtual photons. These act as messengers, constantly exchanged between charged particles and magnetic poles, communicating the electromagnetic force - attraction and repulsion happens due to this exchange. But magnetism comes down to electrons. Electrons obey the Pauli Exclusion Principle which says that two identical electrons can’t be at the same place at the same time. So since for a given orbital, electrons are identical to each other except for their spin orientations, you will only find oppositely spinning electrons together in any orbital of an atom. Quantum mechanically, unpaired electrons in any atom’s shell generally align their spins, that is, spin in the same direction. Why? The wavefunction of parallel spinning electrons interact in such a way that they move further apart, which lowers their repulsive interaction. Why do magnets sometimes attract, and sometimes repel? It boils down to the spin alignment and quantum symmetry of electron wavefunctions in the magnets. #magnetism When two similar poles approach, their electron spins are aligned in opposite ways relative to each other. This arrangement creates interference patterns in their electron wavefunctions, making it energetically unfavorable for electrons to occupy overlapping states. The materials want to avoid that space, and move to a lower energy space which is away from each other. The lower potential energy is away from each other. When opposite poles approach each other, electron spins from one magnet align nicely with spins in the other magnet. Their electron wavefunctions overlap constructively, lowering their combined quantum ener. So, the magnets spontaneously move to that space, that is they move closer together. Overall summary: 1. Electron spin creates tiny quantum magnets. 2. Exchange interactions align electron spins in the lattice structure of materials like iron. 3. Aligned spins produce large-scale magnetic fields. 4. Magnets interact through exchanges of virtual photons which are excitations in the quantum electromagnetic field. 5. Attraction and repulsion results from how electron spins and wavefunctions overlap and interfere quantum mechanically.