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What Is a Particle? (2020)

quantamagazine.org

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Re: What Is a Particle? (2020)

#51

Post by akira2501 »

tambourine_man wrote: post #49
akira2501 wrote: post #42

Earlier quoted context omitted.

I think the distinction is more "we understand it" and "we can explain it." Understanding doesn't generally imply totality of comprehension. Going the other way, you most likely cannot explain why your body or your brain works, yet, here we are, using and understanding them just fine. Which leads to what I was trying to get at. Perhaps our tentative understandings and our means of receiving them are what gets in the…

> yet, here we are, using and understanding them just fine. I think we’re failing miserably precisely because we don’t.

I personally don't think perfection is actually achievable, so I'm completely unwilling to accept your definition of our present state as "failing miserably." That's a rather miserable point of view and I prefer to have and encourage hope.

Re: What Is a Particle? (2020)

#52

Post by woopsn »

prng2021 wrote: post #10
kayo_20211030 wrote: post #3

A particle is a thing you can "look" at, and say "that's a particle". It is whatever one says it is. They're not exactly discovered, they're invented. Fundamental in this context is not so much a word as it is an analogy. And, don't get me wrong, that doesn't mean particles don't exist. They do. But, a particle is whatever we say it is.

We're not asking questions about human constructs like what is moral or what is the ideal form of government. We're trying to understand what the most fundamental building block of reality is, which is something objective. Something independent of whether of not people ever existed. So no, countless people around the world aren't wasting their lives researching particles when the answer is simply, it's whatever we sa…

What can we see? Vapor trails, patterns burned into a plate, etc. The evidence of some "thing" slowing down, perhaps, but really the environment that slowed it down necessarily changing irreversibly. Irreversible effects cannot be arbitrarily small (apparently). We never see a particle, only effects such as these -- if we did see anything else, well, we couldn't possibly remember. Particles are an attempt to explain/theorize evidence that is fundamentally observational.

Re: What Is a Particle? (2020)

#53

Post by divs1210 »

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…

Particle spin explained:

Imagine a ball that’s rotating,

Except it’s not a ball, and

It’s not rotating.

(popular particle physics meme)

From what I understand of QFT, the Universe is made of fields of different types, and a “fundamental particle” is just an excitation (wave) in the corresponding field.

For example, a photon is a wave in the universal electromagnetic field, A charm quark is a wave in the universal charm quark field, etc.

I’m not a trained physicist, so I might be wildly wrong.

Re: What Is a Particle? (2020)

#54

Post by sfink »

kayo_20211030 wrote: post #23
khazhoux wrote: post #13

Earlier quoted context omitted.

I'll go even further and point out that in 2003, it was proven that particles are not , in fact, the friends we made along the way.

Do expand. What happened in 2023?

Yeah, I don't get that, because it seems to me that the friends you make along the way are mathematically indistinguishable from particles being real and having properties. It's a distinction without a difference.

Or at least, I'm interpreting "the friends you make along the way" as the sum total of the effects of a particle on the surrounding world. Saying "the particle doesn't exist, but it has effects X, Y, and Z" is the same as "the particle exists and has effects X, Y, and Z". If a distinction is not observable, then it's meaningless to quibble over whether it's "real" or not.

(Which all just proves that my interpretation isn't the one you were using....)

Re: What Is a Particle? (2020)

#55

Post by danbruc »

criddell wrote: post #26
danbruc wrote: post #22

Earlier quoted context omitted.

I mean I can not speak for you, but I do not think that the problem necessarily is that people think of them as made from some stuff, I think what causes the most trouble is the desire to visualize particles. The trouble is that an electron is an electron and it is nothing like anything you have ever seen in your macroscopic classical world. It shares some aspects with billiard balls and some with water waves but it…

> And electrons being electrons also means that they are not excitations in quantum fields You’re going against the dominant interpretation of QFT here, aren’t you?

I have no idea whether or not most physicist think that there are actually quantum fields in the universe. The Navier–Stokes equations provide a good description of milk mixing into my coffee, but should I therefore conclude that my coffee mug is filled with density and velocity fields and that what coffee really is, is a region in spacetime with a nonzero value of the coffee density field?

Quantum fields have gauge symmetries which means that they are a redundant description, i.e. any given physical situation is represented by an entire equivalence class of field configurations which makes me highly suspicious of there being real quantum fields. Quantum fields are a nice mathematical tool but I do not think we have any good reasons to think they are real, but I am not a physicist and I am certainly in dangerous half-knowledge territory here.

I have been wondering for years whether this might actually be a non-issue, could the universe secretly have fixed a gauge and just ran with it? Or would this somehow be inconsistent?

Re: What Is a Particle? (2020)

#56

Post by mensetmanusman »

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…

https://youtu.be/j2oSyAfPzWg?si=bwM2NAsORzkqLQLk

Fun fields discussion on what particles are…

Re: What Is a Particle? (2020)

#57

Post by mensetmanusman »

akira2501 wrote: post #37
Biologist123 wrote: post #29

I feel a curious mix of excitement and disconcerted to discover humans don’t really understand what matter is. Reading the article, I understood so little of it. And I guess it’s because so much of the language is just words chosen through some sort of consensus to represent an abstract idea itself composed of such words-idea-representations which I’ve never encountered before.

We understand matter perfectly well. Look at the size and scope of the engineering marvels that have been constructed on the surface of this planet and in our low orbit. It's astonishing. What we don't understand is the fundamental structure of that matter or of our Universe. I personally feel that the people ostensibly "in charge" of this effort are a little chagrined at their decades of inability to produce not onl…

We understand _low_ resolution matter.

Re: What Is a Particle? (2020)

#58

Post by geye1234 »

kayo_20211030 wrote: post #41
fragmede wrote: post #35

Earlier quoted context omitted.

discovery vs invention is a question in mathematics as well. trying to say they're invented isn't clever, it's just a trick of language, like how gravity is merely a theory. particles are theorized to exist via theoretical physics and math, and then tested for experimentally. or as the saying goes, all models are wrong, some are useful.

I can't find the reference at the moment. But, I think it was about the "creation" of the quark. (I'll find it eventually). Either way, a search for reality, no matter how far we've progressed thus far, is either a search for a platonic reality, or an experimental reality. The former is "discovery" and the latter is "invention". It really doesn't matter. I don't think, right now, we're quite smart enough to pry into…

It's both discovery and experiment (but not invention). Forms are real, but not in the way Plato thought. He thought they existed in some empyrean realm. In reality, they exist in objects themselves. We discover what a thing's form is by experimenting with (or on) it. Aristotle was largely right.

The big philosophical problem with much of this is that people assume that the smallest things are the most fundamental. So people think that stuff, whatever that stuff is, is fundamentally made up of much smaller stuff, and that stuff is fundamentally made of yet smaller stuff, and so the smaller you get, the more fundamental you get. And so (they think) if you want to work out what is really going on at any layer of reality, you need to figure out what the smallest possible things are.

Yet this is ultimately a philosophical posit -- it's not empirically-informed. There's no good reason for thinking it.

To be clear, none of this is about physicists doing physics. It's about the philosophy that many people bring into, and therefore take away from, these kinds of discussions.

Re: What Is a Particle? (2020)

#59

Post by lisper »

aaa_aaa wrote: post #50
lisper wrote: post #45

Earlier quoted context omitted.

Richard Feynman gave what I consider to be the best possible answer to questions like this: https://www.youtube.com/watch?v=Q1lL-hXO27Q

At first I was impressed with that video. Then I felt he does not have an answer and unnecessarily gets edgy with it, because question is valid.

> he does not have an answer

Well, yeah. That's the whole point.

Re: What Is a Particle? (2020)

#60

Post by graycat »

Issues:

(1) With Itself:

Consider Young's double slit experiment: So, have plane with two slits and some distance away a parallel plane with detectors. (A) Several times, shoot a photon at the slit. Observe that the detection locations form parallel lines, i.e., fringes. (B) Cover one slit, repeat, and observe that the detection locations from a smooth hill without fringes.

So, from (A) we conclude that the something about the photon went through both slits and interacted with itself to form the fringes, the ones we didn't see from (B).

Q. Between the two planes, where was the energy?

(2) Mass and Charge

Set aside (1) with its photons and two planes.

Now one at a time shoot electrons, i.e., with not just energy but also mass and charge. And shoot the electrons at a beam splitter, i.e., a plane, partially transparent to the electrons, and at 45 degrees to the path of the electrons.

Some electrons pass through the plane with no change in direction and some get deflected 90 degrees.

On the paths after the plane, have some very sensitive detectors for mass and charge. These detectors are distant enough that what they do cannot affect the electron, i.e., the electron does not know about the detectors.

Q. What do the detectors read? For each of the two paths, whole mass and charge, half, or something else?

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