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What Is a Particle? (2020)

quantamagazine.org

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Re: What Is a Particle? (2020)

#141

Post by fasa99 »

travisjungroth wrote: post #133
binary132 wrote: post #130

Earlier quoted context omitted.

One of the ultimately epistemological puzzles to me is the question of what math really is. Like, obviously, it is fundamentally descriptive. “Two and two makes four” is pretty straightforwardly talking about something “out there”. And when we’re talking about fields, we are clearly also describing something that is really happening, that is really “out there”; it’s not the math itself that is the real thing, but rat…

One way of viewing it is that math is games. Not in the winner sense, but in the activities with rules sense. Addition is a game. Some games make you better at other activities. Like, playing chess could make you better at logistics because you’re practicing planning and managing losses. Some games match some real world situations so tightly that we can go through them step by step and solve the real world situation…

The idea that it's an abstraction is 100% accurate. That physics is a discrete set of fields with field rules and interaction rules, and what we observe is a scaffold on top of that. It's like okay, let's say the math is right and we have a set of fields, what are they and where are they from, how do we manipulate them. Then the physicists, often driven by ego, is want for an explanation and points to vibrating strings and such, and finally they knock on the door of the empiric physicist and say "can you do an experiment to show that I'm right" "sure, build a machine the size of the universe and I could test that" and that's the state of physics the last gorillion years

https://www.youtube.com/watch?v=FYJ1dbyDcrI

Re: What Is a Particle? (2020)

#143

Post by jakey_bakey »

> "It has been thought of as many things"

This makes me remember the time I looked at a random book at my university library, and it happened to be a physics book from 1905.

Which was both fascinating and unintentionally hilarious due to it proudly asserting that we knew most of physics now because we knew about atoms, and assuring the plum pudding model as how atoms worked.

n.b. Plum Pudding was the old-school idea that atoms were a positively-charged blob with negative electrons embedded. It was refuted when you measure the radiation scattering patterns off gold foil and discover that, actually, there's an extremely dense nucleus.

Re: What Is a Particle? (2020)

#144

Post by jerf »

lottin wrote: post #125
binary132 wrote: post #61

Earlier quoted context omitted.

I get it but I still think these sorts of concepts are also just another level of mathematical abstraction that isn’t necessarily “really what it is” any more than a rotating ball or a math equation or any of the other ideas are “really what it is”

It's very frustrating. The idea that the universe is made of fields is nonsensical. I don't understand why so many physicists keep saying that.

The Universe May Do As It Damned Well Pleases.

Maybe it is "made of fields", maybe it isn't, but "I think that's nonsense", which is just a gussied up way of saying "my intuition rejects that", is not a valid judgment method. The universe does not check with our intuition before doing what it Damned Well Pleases.

Re: What Is a Particle? (2020)

#145

Post by lottin »

dgoodell wrote: post #131
lottin wrote: post #127

Earlier quoted context omitted.

No... a field is mathematical representation. The universe is most definitely NOT made of fields.

Are you saying that the universe cannot be represented by mathematics? I imagine you could use that argument to shoot down pretty much any explanation.

I'm saying that a mathematical representation of a physical phenomenon isn't the physical phenomenon.

Re: What Is a Particle? (2020)

#146

Post by agumonkey »

jakey_bakey wrote: post #143

> "It has been thought of as many things" This makes me remember the time I looked at a random book at my university library, and it happened to be a physics book from 1905. Which was both fascinating and unintentionally hilarious due to it proudly asserting that we knew most of physics now because we knew about atoms, and assuring the plum pudding model as how atoms worked. n.b. Plum Pudding was the old-school idea…

while I often wonder what part of today's knowledge will appear brutally obsolete for those born in the 2100s

Re: What Is a Particle? (2020)

#147

Post by lottin »

jerf wrote: post #144
lottin wrote: post #125

Earlier quoted context omitted.

It's very frustrating. The idea that the universe is made of fields is nonsensical. I don't understand why so many physicists keep saying that.

The Universe May Do As It Damned Well Pleases. Maybe it is "made of fields", maybe it isn't, but "I think that's nonsense", which is just a gussied up way of saying "my intuition rejects that", is not a valid judgment method. The universe does not check with our intuition before doing what it Damned Well Pleases.

So you think the universe might be made of, say, subordinate clauses?

Re: What Is a Particle? (2020)

#148

Post by evanb »

ziofill wrote: post #87
AlbertCory wrote: post #2

I'm reading "The Big Picture" (Sean Carroll) right now. I'd love to have a real physicist explain this, but: When we think of what a particle IS, we often think as though it were dirt, or a billiard ball, or something. As though there were some other substance of which it's made. At least I do. But the definition is as low as you can go. It's hard to wrap your head around that. Unless you're trained to do so, I guess…

Physicist here. You are right that the mental picture we get when we use the term “particle” is a little ball or something like that. It is unfortunately a confusing name… You need to begin with a field, like the electromagnetic field for instance. When you look at its properties like energy, polarization and so on, in order to write down a state of the field you need to specify all of them in a way or another. In qu…

Also a physicist.

It's not quite right to call basis vectors particles, even in a free field theory. The particles correspond better to the creation / ladder operators that take you from one Hamiltonian eigenstate to another.

In a perturbative interacting case, people still think of particles as these same ladder operators, but they don't connect eigenstates so simply (the interactions generically mix all the states with the same quantum numbers).

In a strongly interacting case the story is even more subtle, because composite operators may be closer to the ladder operators between the asymptotic states, even though they're built of other... particles? Language isn't great in this instance.

Re: What Is a Particle? (2020)

#149

Post by lottin »

bbor wrote: post #138
lottin wrote: post #127

Earlier quoted context omitted.

No... a field is mathematical representation. The universe is most definitely NOT made of fields.

Ok fair: they're things that right now are best understood using the term Field. I don't understand what kind of answer you're hoping for that would be better than this -- what kind of answer to "what is a particle" wouldn't be describable by mathematics? By saying "the universe is fields", I'm saying "it's distributions of energy across spacetime". That's seemingly a consensus. Why demand that that energy must also…

Let's say we describe a particle as being an excitation of a field. Can't we describe any physical phenomenon in the same way? For example, describe a football as an excitation of the football field. I think we all agree that this description does a terrible job of actually describing a football. In fact, I don't think it can be called a description at all. Likewise, I find describing a particle as an excitation of a field to be equally unsatisfactory.

Re: What Is a Particle? (2020)

#150

Post by scotty79 »

atemerev wrote: post #103
scotty79 wrote: post #100

Earlier quoted context omitted.

So basically a tree doesn't fall in the forest if there's no one around to see it? There's no forest and there are not trees. It's all spawned as needed when we go for a hike? Kinda arrogant don't you think?

A tree interacts with many things, not just human observers. We are not special in any way. This discreteness is only relevant and/or observable when we look at individual particles that rarely interact with anything else.

So we have no idea what's observable in this generic way and what's not.
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