3 ms·

When you think about particles as excitations of a field, the indistinguishable nature of said particles stops being such a puzzle.

daxfohl 8y ago
But the concept of a field itself was troubling to 18-19th century physicists. "So you put this (mass/charge/entanglement/whatever) here and automagically there's this whole force that extends across the universe in zero time? How? Why?" Philosophically I don't know if this question has ever been answered satisfactorily. But over the last 100 years fields have become so mathematically convenient that they're too hard not to use.
- dbasedweeb 8y ago
  Well those 18th-19th century anything didn’t have a concept of entanglement or FTL, they were struggling with the notion that light, gravity, and other forces could propagate without a medium. They saw that waves could be transmitted through water, sound through air, and the idea that light or gravity could be transmitted through vacuum was baffling. Their resolution to the issue was to propose the existence of a substance which was invisible, intangible, but which permeated everything: the luminiferous ether. Light, in their understanding, wasn’t really moving through a vacuum, but this ever-present “stuff” instead. That started to fall out of favor long after the 18th century, and was finally conclusively shot down by Michelson and Morley with their interferometry. The problem Einstein and others grappled with was different, and concerned the fact that according to relativity nothing should exceed c. Entangled particles seemed to violate that principle, because the collapse to a given pair of states was instantaneous. The modern resolution to that is more practical than philosophical, and points out that information isn’t transmitted faster than light in entangled particles. Information propagates at or below c, even though at some scale entangled particles are statistically correlated. Relativity is only violated, and causality threatened if information is transmitted FTL, but entanglement doesn’t allow for that. You need a classical channel make entanglement work for communication, and that classical channel is going to be no faster than light. Without a classical channel, entanglement just gives you random noise.
  - goatlover 8y ago
    > Relativity is only violated, and causality threatened if information is transmitted FTL, but entanglement doesn’t allow for that. You need a classical channel make entanglement work for communication, and that classical channel is going to be no faster than light. Without a classical channel, entanglement just gives you random noise. But none of that answers the 18th-19th century Physicists question about how fields extend across the universe, or how light propagates in empty space. What the hell is a field anyway? Also, it doesn't explain how the expansion of space happens, what made inflation happen, and what dark energy is.
    - dbasedweeb 8y ago
      A very smart guy named Alfred Korzybski said, “The map is not the territory.” It’s important to not get too hung up on epistemological implications of our models of reality, because they are just models. On a practical level a field is something which has a value at every point, that value can be a scalar, vector, or tensor depending on the nature of the field. For some good discussion I think this could help: https://physics.stackexchange.com/questions/13157/what-is-a-field-really https://physics.stackexchange.com/questions/13157/what-is-a-... Now, it is very easy to get hung up on this "Is it real or not" thing, and most people do for at least a while, but please just put it aside. When you peer really hard into the depth of the theory, it turns out that it is hard to say for sure that stuff is "stuff". It is tempting to suggest that having a non-zero value of mass defines "stuffness", but then how do you deal with the photo-electric effect (which makes a pretty good argument that light comes in packets that have enough "stuffness" to bounce electrons around)? All the properties that you associate with stuff are actually explainable in terms of electro-magnetic fields and mass (which in GR is described by a component of a tensor field!). And round and round we go. Light doesn’t propagate in empty space, because space isn’t empty, it’s permeated with quantum fields in constant flux. What light doesn’t require is a medium, and a field is not a medium. The problem here is that these theories are really described in terms of a bunch of math, and when we use words to describe those theories, something is lost in translation. There are no words that fully capture what a field is in QFT, you must use math. Once you adopt that perspective, inflation would just be the result of another field with particular properties (esp. a given range of potential energy curves). Of course, inflation is an untested theory, and there are competing ones which try to explain the apparent homogeneity and isotropy of the universe. Inflation is probably the most popular, but it doesn’t rest on the kind of firm foundation that QED does.

daxfohl 8y ago

But the concept of a field itself was troubling to 18-19th century physicists. "So you put this (mass/charge/entanglement/whatever) here and automagically there's this whole force that extends across the universe in zero time? How? Why?" Philosophically I don't know if this question has ever been answered satisfactorily. But over the last 100 years fields have become so mathematically convenient that they're too hard not to use.

dbasedweeb 8y ago
Well those 18th-19th century anything didn’t have a concept of entanglement or FTL, they were struggling with the notion that light, gravity, and other forces could propagate without a medium. They saw that waves could be transmitted through water, sound through air, and the idea that light or gravity could be transmitted through vacuum was baffling. Their resolution to the issue was to propose the existence of a substance which was invisible, intangible, but which permeated everything: the luminiferous ether. Light, in their understanding, wasn’t really moving through a vacuum, but this ever-present “stuff” instead. That started to fall out of favor long after the 18th century, and was finally conclusively shot down by Michelson and Morley with their interferometry. The problem Einstein and others grappled with was different, and concerned the fact that according to relativity nothing should exceed c. Entangled particles seemed to violate that principle, because the collapse to a given pair of states was instantaneous. The modern resolution to that is more practical than philosophical, and points out that information isn’t transmitted faster than light in entangled particles. Information propagates at or below c, even though at some scale entangled particles are statistically correlated. Relativity is only violated, and causality threatened if information is transmitted FTL, but entanglement doesn’t allow for that. You need a classical channel make entanglement work for communication, and that classical channel is going to be no faster than light. Without a classical channel, entanglement just gives you random noise.
- goatlover 8y ago
  > Relativity is only violated, and causality threatened if information is transmitted FTL, but entanglement doesn’t allow for that. You need a classical channel make entanglement work for communication, and that classical channel is going to be no faster than light. Without a classical channel, entanglement just gives you random noise. But none of that answers the 18th-19th century Physicists question about how fields extend across the universe, or how light propagates in empty space. What the hell is a field anyway? Also, it doesn't explain how the expansion of space happens, what made inflation happen, and what dark energy is.
  - dbasedweeb 8y ago
    A very smart guy named Alfred Korzybski said, “The map is not the territory.” It’s important to not get too hung up on epistemological implications of our models of reality, because they are just models. On a practical level a field is something which has a value at every point, that value can be a scalar, vector, or tensor depending on the nature of the field. For some good discussion I think this could help: https://physics.stackexchange.com/questions/13157/what-is-a-field-really https://physics.stackexchange.com/questions/13157/what-is-a-... Now, it is very easy to get hung up on this "Is it real or not" thing, and most people do for at least a while, but please just put it aside. When you peer really hard into the depth of the theory, it turns out that it is hard to say for sure that stuff is "stuff". It is tempting to suggest that having a non-zero value of mass defines "stuffness", but then how do you deal with the photo-electric effect (which makes a pretty good argument that light comes in packets that have enough "stuffness" to bounce electrons around)? All the properties that you associate with stuff are actually explainable in terms of electro-magnetic fields and mass (which in GR is described by a component of a tensor field!). And round and round we go. Light doesn’t propagate in empty space, because space isn’t empty, it’s permeated with quantum fields in constant flux. What light doesn’t require is a medium, and a field is not a medium. The problem here is that these theories are really described in terms of a bunch of math, and when we use words to describe those theories, something is lost in translation. There are no words that fully capture what a field is in QFT, you must use math. Once you adopt that perspective, inflation would just be the result of another field with particular properties (esp. a given range of potential energy curves). Of course, inflation is an untested theory, and there are competing ones which try to explain the apparent homogeneity and isotropy of the universe. Inflation is probably the most popular, but it doesn’t rest on the kind of firm foundation that QED does.