8 ms·

Aether has a specific definition and it still does not exist. It was not rediscovered. QFT is not aether-like. Aether was a substance filling all space, while

by emrah 2y ago

Aether has a specific definition and it still does not exist. It was not rediscovered. QFT is not aether-like. Aether was a substance filling all space, while QFT fields like higgs are not physical at all (but rather give rise to physical properties)

calf 2y ago
How does something not physical give rise to physical properties? Saying that way makes it sounds like a logical conceit is being used.
- TheOtherHobbes 2y ago
  It organises stuff instead of being stuff. Which is less of a logical conceit, and more metaphysics. No one knows what quantum fields are made of. There are various ideas (loop quantum gravity, causal dynamical triangulation, others...) but QFT defines what quantum fields do, not what their component parts are at a more fundamental level.
wyager 2y ago
> QFT fields like higgs are not physical at all (but rather give rise to physical properties) I think this is a nonsense cop-out and bad ontology. What does it mean to "be physical" if not to be causally downstream of other physical effects?
Maxatar 2y ago
What was the "specific" definition of the aether? It looks from reviewing the history that there was no consensus on what the aether was or what its properties were. Interestingly enough what I did manage to find is a lecture given by Einstein in 1920 where he argues that the ether is in fact essential towards the understanding of general relativity, and that it could be through the ether that gravity and electromagnetism are unified: https://www.researchgate.net/publication/358617464_Ether_and_the_Theory_of_Relativity https://www.researchgate.net/publication/358617464_Ether_and...
- eigenket 2y ago
  > What was the "specific" definition of the aether? TL:DR the aether has a reference frame. This is exactly what it's inventors wanted and exactly what modern things don't have. Here is the long version: When you put together a couple of the constants of classical electromagnetic theory (specifically the quantities called the permitivity and permeability of free space) you get out a quantity which has the units of a speed. You get this thing which is measured in metres per second. Now if you're a Victorian era scientist, and you have fully internalised Gallilean relativity and Newtonian mechanics then this is absolutely, completely, insane. There is no way in their worldview for a speed to exist in isolation, without a reference frame for it to be measured with respect to. If I measure a guy on a bike going at 10 miles per hour, and a guy in a car going at 30 miles per hour past him then the guy on the bike sees the car going at 20 miles per hour relative to him. If I sit opposite you on a train I measure your speed to be 0, even though we're both moving at 100+ km/hour. Speeds are (for Victorian scientists) completely relative. So they have the theory of electromagnetism, which seems to be giving amazingly accurate predictions, except that it also gives you this apparently absolute speed, which makes no sense. Someone realises pretty fast that it's about the speed that light goes. So what do they do? They propose the existence of this "aether" stuff which is everywhere at all times and critically which has a reference frame. The aether provides a reference frame for the speed of light and the crazy meaningless absolute speed they didn't know what to do with now makes sense, it's relative like any other speed, but the magic quantity they got is the speed in the aether's reference frame. Of course a few decades later Michelson and Morley show that this idea doesn't work, in an incredibly beautiful experiment, and the aether theory starts to look shaky. A few years after that Einstein (with input from people like Lorentz) cooks up special relativity which is almost like Gallilean relativity in that almost all speeds are relative, except specifically the speed of light is not. The speed of light is absolute, just as it has to be because of the way it pops out of electromagnetism.
- simpaticoder 2y ago
  The aether (or just ether) was assumed to be the substance in which light waves waved, just as air is the substance that sound waves. If this substance existed it was likely that the Earth was moving through it at some velocity, and the Michelson-Morley experiment famously showed that this is not so. There were also observations of Jupiter's moons. These null results led to Lorentz' quantification of what would become Einstein's definition of special relativity in 1905. Our confidence in SR is so strong now that c is defined and length unit defined as the distance light travels during a set time.
halyconWays 2y ago
> while QFT fields like higgs are not physical at all Phew, I feel better now. Non-physical scalar and tensor fields permeating all of expanding spacetime in a non-physical manner give rise to physical behavior via local nonphysical wavefunction collapse that we call excitations.
- criddell 2y ago
  That's why the mathematical universe hypothesis (everything is built from mathematical structures) seems likely to me.
  - halyconWays 2y ago
    It's sort of unsatisfying to say that math has the ability to experience itself, though
    - criddell 2y ago
      Is it? That’s basically what a conscious AI would be and I have a hard time coming up with reasons why a software brain couldn’t replace a biological brain.
  - TheOtherHobbes 2y ago
    It seems incredibly unlikely to me. It's more likely all physics is argument by analogy from limited human experiences, and math is just a culturally consistent subset of that. What look like genius predictions are mostly (Einstein aside...) generations of post docs throwing equations at their whiteboards to see what sticks. A few happen to be confirmed by experiment. Most are quietly forgotten. I strongly suspect we literally can't begin to imagine what's really going on.
    - criddell 2y ago
      > I strongly suspect we literally can’t begin to imagine what’s really going on. I also happen to believe that might be true. In the same way a dog will never understand single variable calculus, there probably are concepts that are out of reach for us.

by emrah 2y ago

calf 2y ago

How does something not physical give rise to physical properties? Saying that way makes it sounds like a logical conceit is being used.

TheOtherHobbes 2y ago
It organises stuff instead of being stuff. Which is less of a logical conceit, and more metaphysics. No one knows what quantum fields are made of. There are various ideas (loop quantum gravity, causal dynamical triangulation, others...) but QFT defines what quantum fields do, not what their component parts are at a more fundamental level.

wyager 2y ago

> QFT fields like higgs are not physical at all (but rather give rise to physical properties) I think this is a nonsense cop-out and bad ontology. What does it mean to "be physical" if not to be causally downstream of other physical effects?

Maxatar 2y ago

What was the "specific" definition of the aether? It looks from reviewing the history that there was no consensus on what the aether was or what its properties were. Interestingly enough what I did manage to find is a lecture given by Einstein in 1920 where he argues that the ether is in fact essential towards the understanding of general relativity, and that it could be through the ether that gravity and electromagnetism are unified: https://www.researchgate.net/publication/358617464_Ether_and_the_Theory_of_Relativity https://www.researchgate.net/publication/358617464_Ether_and...

eigenket 2y ago
> What was the "specific" definition of the aether? TL:DR the aether has a reference frame. This is exactly what it's inventors wanted and exactly what modern things don't have. Here is the long version: When you put together a couple of the constants of classical electromagnetic theory (specifically the quantities called the permitivity and permeability of free space) you get out a quantity which has the units of a speed. You get this thing which is measured in metres per second. Now if you're a Victorian era scientist, and you have fully internalised Gallilean relativity and Newtonian mechanics then this is absolutely, completely, insane. There is no way in their worldview for a speed to exist in isolation, without a reference frame for it to be measured with respect to. If I measure a guy on a bike going at 10 miles per hour, and a guy in a car going at 30 miles per hour past him then the guy on the bike sees the car going at 20 miles per hour relative to him. If I sit opposite you on a train I measure your speed to be 0, even though we're both moving at 100+ km/hour. Speeds are (for Victorian scientists) completely relative. So they have the theory of electromagnetism, which seems to be giving amazingly accurate predictions, except that it also gives you this apparently absolute speed, which makes no sense. Someone realises pretty fast that it's about the speed that light goes. So what do they do? They propose the existence of this "aether" stuff which is everywhere at all times and critically which has a reference frame. The aether provides a reference frame for the speed of light and the crazy meaningless absolute speed they didn't know what to do with now makes sense, it's relative like any other speed, but the magic quantity they got is the speed in the aether's reference frame. Of course a few decades later Michelson and Morley show that this idea doesn't work, in an incredibly beautiful experiment, and the aether theory starts to look shaky. A few years after that Einstein (with input from people like Lorentz) cooks up special relativity which is almost like Gallilean relativity in that almost all speeds are relative, except specifically the speed of light is not. The speed of light is absolute, just as it has to be because of the way it pops out of electromagnetism.
simpaticoder 2y ago
The aether (or just ether) was assumed to be the substance in which light waves waved, just as air is the substance that sound waves. If this substance existed it was likely that the Earth was moving through it at some velocity, and the Michelson-Morley experiment famously showed that this is not so. There were also observations of Jupiter's moons. These null results led to Lorentz' quantification of what would become Einstein's definition of special relativity in 1905. Our confidence in SR is so strong now that c is defined and length unit defined as the distance light travels during a set time.

halyconWays 2y ago

> while QFT fields like higgs are not physical at all Phew, I feel better now. Non-physical scalar and tensor fields permeating all of expanding spacetime in a non-physical manner give rise to physical behavior via local nonphysical wavefunction collapse that we call excitations.

criddell 2y ago
That's why the mathematical universe hypothesis (everything is built from mathematical structures) seems likely to me.
- halyconWays 2y ago
  It's sort of unsatisfying to say that math has the ability to experience itself, though
  - criddell 2y ago
    Is it? That’s basically what a conscious AI would be and I have a hard time coming up with reasons why a software brain couldn’t replace a biological brain.
- TheOtherHobbes 2y ago
  It seems incredibly unlikely to me. It's more likely all physics is argument by analogy from limited human experiences, and math is just a culturally consistent subset of that. What look like genius predictions are mostly (Einstein aside...) generations of post docs throwing equations at their whiteboards to see what sticks. A few happen to be confirmed by experiment. Most are quietly forgotten. I strongly suspect we literally can't begin to imagine what's really going on.
  - criddell 2y ago
    > I strongly suspect we literally can’t begin to imagine what’s really going on. I also happen to believe that might be true. In the same way a dog will never understand single variable calculus, there probably are concepts that are out of reach for us.