3 ms·

I've been bothering myself with the same question. This rabbit hole in the wikipedia has led me to a dead-end explanation: those iron filings are pulled by virt

by akomtu 5y ago

I've been bothering myself with the same question. This rabbit hole in the wikipedia has led me to a dead-end explanation: those iron filings are pulled by virtual photons created by the magnet, those virtual photons are completely virtual and cannot be observed, except for the fact that they somehow pull the filings despite being virtual (this must be a small incursion of the purely mathematical world into reality). I've concluded that magnetism is an unexplained phenomenon, just like gravity: we have accurate formulas, but nobody knows what those formulas describe. For intuitive understanding, I see a magnet as a well, except that this well can be moved around and has two poles. Just like a regular well, things fall into it at no expense to the well, because the well isn't really a "thing" that pulls other things by force.

hither_shores 5y ago
> This rabbit hole in the wikipedia has led me to a dead-end explanation Trying to teach yourself physics by reading wikipedia is like trying to learn how to program by reading the C++ standard. It's a fine resource, but not for that. You need an introductory physics textbook, not an encyclopedia. Griffith's Introduction to Electrodynamics is a classic choice. > those iron filings are pulled by virtual photons created by the magnet No. Virtual particles are part of a notational scheme for carrying out certain computations in quantum field theory. They're not particles, and they're definitely not involved in classical electromagnetism. > I've concluded that magnetism is an unexplained phenomenon, just like gravity: we have accurate formulas, but nobody knows what those formulas describe. The formulas, ultimately, describe the relationship between our observations. This is the only sense in which we ever explain anything, and a sense in which magnetism and gravity are both very well-explained. > For intuitive understanding, I see a magnet as a well, except that this well can be moved around and has two poles. You should not try to understand electromagnetism intuitively yet. You haven't built the right intuitions, and to do that you first need to tear down your wrong ones.
l33tman 5y ago
By that logic you can't observe anything or explain anything, though. All the force carrying bosons (like the photon) have to interact with fermions (the electrons and quarks that make up your equipment and your body). Some of the interactions happen due to on-shell photons ("light") but most happen due to completely off-shell photons (EM force). They are really the same interaction. Don't get hung up on the "virtual" in the lingo about particles. All particles are more or less "virtual" depending on how you analyze the problem. I'm sorry there is not a more intuitive explanation of this.. The underlying QFT building blocks are so far from classical physics. Even concepts like energy and momentum are in some sense emergent properties that lose most of their classical intuition "at the bottom", this is reflected by the Heisenberg uncertainty relationship for example.

by akomtu 5y ago

hither_shores 5y ago

> This rabbit hole in the wikipedia has led me to a dead-end explanation Trying to teach yourself physics by reading wikipedia is like trying to learn how to program by reading the C++ standard. It's a fine resource, but not for that. You need an introductory physics textbook, not an encyclopedia. Griffith's Introduction to Electrodynamics is a classic choice. > those iron filings are pulled by virtual photons created by the magnet No. Virtual particles are part of a notational scheme for carrying out certain computations in quantum field theory. They're not particles, and they're definitely not involved in classical electromagnetism. > I've concluded that magnetism is an unexplained phenomenon, just like gravity: we have accurate formulas, but nobody knows what those formulas describe. The formulas, ultimately, describe the relationship between our observations. This is the only sense in which we ever explain anything, and a sense in which magnetism and gravity are both very well-explained. > For intuitive understanding, I see a magnet as a well, except that this well can be moved around and has two poles. You should not try to understand electromagnetism intuitively yet. You haven't built the right intuitions, and to do that you first need to tear down your wrong ones.

l33tman 5y ago

By that logic you can't observe anything or explain anything, though. All the force carrying bosons (like the photon) have to interact with fermions (the electrons and quarks that make up your equipment and your body). Some of the interactions happen due to on-shell photons ("light") but most happen due to completely off-shell photons (EM force). They are really the same interaction. Don't get hung up on the "virtual" in the lingo about particles. All particles are more or less "virtual" depending on how you analyze the problem. I'm sorry there is not a more intuitive explanation of this.. The underlying QFT building blocks are so far from classical physics. Even concepts like energy and momentum are in some sense emergent properties that lose most of their classical intuition "at the bottom", this is reflected by the Heisenberg uncertainty relationship for example.