First collisions at the LHC with unprecedented Energy! (Ask a particle physisicist)

[Pyrrho]

That sounds lovely.  The only way it could be much better would be to have an entire bottle of wine, and someone to share it with and...

From The Rubáiyát of Omar Khayyám, as translated by Edward FitzGerald, fifth edition:

XII.


 A Book of Verses underneath the Bough,
 A Jug of Wine, a Loaf of Bread--and Thou
   Beside me singing in the Wilderness--
 Oh, Wilderness were Paradise enow!

https://en.wikisource.org/wiki/The_Rubai...h_edition)

Lovely - I'd only heard of the Rubaiyat in connection with the mysterious dead spy chiffre case, but never read any of it...

I highly recommend it.  For English, I like Edward FitzGerald, and I think I like his 5th (his final) edition best, though all of his editions are good.  For German, I have no clue what translation would be good, if any.

Of course, since we are talking about poetry, translations do not keep to the exact meaning of the original, and in this case, typically only some of the quatrains are translated; I do not know if anyone has translated them all.

But, it would be nice, relaxing beneath a tree on a warm day, with your head in your wife's lap while she reads The Rubáiyát  to you, with her fingers gently running through your hair, drinking wine and having some good bread and other food.

Anyway, your description of your time in a garden in the shade of a tree, drinking wine, made me think of such kinds of things.

So again, you wonder whether or how we can talk about particles without knowing what particles actually are. As I have alluded to earlier, I don't think this is necessarily in the realm of science - but - I also believe that we regularly leave the realm of science when we talk about nature. This is a deep philosophy of science question and I am no philosopher of science, so I can only offer you a half baked cake of my own making. I think the question what particles really are, might possibly not be a valid question. My impression is that we can't help but talk about the objects and goings on in the world in terms of our theories about these objects, and that only in the framework of a theory a multitude of phenomena can be unified into a single object. What is a cup of coffee really? Is it still the same cup if you rotate it 180° and why? In order to talk about *the cup*, we have to relate a multitude of phenomena in different channels, touch, sight, and its reaction to touch, and a theory of rigid  rotations in space and how they form equivalence classes between objects, all have to relate these things in a theoretical construct you call *the cup*. I don't think particle physics is all that different, except that quantum weirdness makes it harder to express the state of an object in everyday language.

Concerning the second question, I have wondered that myself. The interpretation of forces as particle exchange is an intuition that comes out of the mathematical construction of Feynman diagrams. It is real work to try and map this question (how do the particles that are exchanged decide to get flying, do they see their goal?) to the maths of the derivation of feynman diagrams. My preliminary answer is thusly: Particles send off virtual particles all the time in this picture. If another is in sight, it gets caught. But this does not explain why particles don't "lose " energy via virtual particles all the time.

I have noticed this distinction in your earlier posts.  I seem to recall you alluding to the distinction between metaphysics and science in the distant past, but I can give an example from yesterday (which is why I gave the post kudos):

Brilliant questions, will try to address later. But yes, I talk of theory objects as if they are objects in nature. I don't know what is *really* going on, and that's possibly not a phtsics question

It is recognizing and keeping clear on this distinction that shows really good sense, which is one of the reasons I like and respect you.

Lest anyone suppose I am denigrating philosophy, I will make a slight digression before getting to what I want to say.  In the history of philosophy, among the ancients, Plato and Aristotle are the biggest names in philosophy.   Among modern philosophers, David Hume and Immanuel Kant are generally regarded as the most important.  I mention this so that everyone will see I am not quoting a fringe philosopher, but one of the most respected philosophers of all time.

Here is something Hume had to say on this subject:


When we run over libraries, persuaded of these principles, what havoc must we make? If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity or number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: for it can contain nothing but sophistry and illusion.

http://oll.libertyfund.org/titles/341#Hume_0222_328


Usually, though, I am content to quote Oscar Wilde in connection with this topic:


Ah! that is clearly a metaphysical speculation, and like most metaphysical speculations has very little reference at all to the actual facts of real life, as we know them.

— Gwendolen, in The Importance of Being Earnest by Oscar Wilde
http://www.gutenberg.org/files/844/844-h/844-h.htm


Anyway, I appreciate the fact that you are a scientist, and not a metaphysician.  It has not gone unnoticed.

[JuliaL]

So again, you wonder whether or how we can talk about particles without knowing what particles actually are.

---

As I have alluded to earlier, I don't think this is necessarily in the realm of science - but - I also believe that we regularly leave the realm of science when we talk about nature. This is a deep philosophy of science question and I am no philosopher of science, so I can only offer you a half baked cake of my own making. I think the question what particles really are, might possibly not be a valid question. My impression is that we can't help but talk about the objects and goings on in the world in terms of our theories about these objects, and that only in the framework of a theory a multitude of phenomena can be unified into a single object. What is a cup of coffee really? Is it still the same cup if you rotate it 180° and why? In order to talk about *the cup*, we have to relate a multitude of phenomena in different channels, touch, sight, and its reaction to touch, and a theory of rigid  rotations in space and how they form equivalence classes between objects, all have to relate these things in a theoretical construct you call *the cup*. I don't think particle physics is all that different, except that quantum weirdness makes it harder to express the state of an object in everyday language.

---

I see us chasing finer and finer structure at higher and higher energies without ever seeing an end.
It used to be that a mustard seed was the smallest thing.  
Now it's some colored, flavored, charmed thing with a made-up name you tell me actually exists.
I think you know what ultimate particle reality is and are keeping the rest of us ignorant to scam more grant money.

Concerning the second question, I have wondered that myself. The interpretation of forces as particle exchange is an intuition that comes out of the mathematical construction of Feynman diagrams. It is real work to try and map this question (how do the particles that are exchanged decide to get flying, do they see their goal?) to the maths of the derivation of feynman diagrams. My preliminary answer is thusly: Particles send off virtual particles all the time in this picture. If another is in sight, it gets caught. But this does not explain why particles don't "lose " energy via virtual particles all the time.

I thought (you said in post #127) that virtual particles didn't carry enough energy to exist.  Are you saying they could still take a little away from the real ones?  
Less than a quantum?  Can they do that?
What means "in sight?"  Is it strictly location, location, location?  It can't be what's normally thought of as sight by us big folks.

But thanks again for translating the math model to more everyday concepts.
When things get really really small they get really really weird.
https://en.wikipedia.org/wiki/Let%27s_Get_Small

I guess that at that scale, what happens in the transitions might be unknowable.
I just can't shake the idea that there has to be a process whereby something is emitted for there to be an emission.

Reality, what a concept.
BTW, do the philosophers of science actually understand what you do? Or are they just faking it?

[Pyrrho]

...
BTW, do the philosophers of science actually understand what you do? Or are they just faking it?

The answer to that is going to depend on which ones you have in mind.  For the most part, I think they don't understand what people like Alex do, and are just faking it, writing and speaking a good deal of nonsense.  Fortunately, scientists basically ignore them and just go about their business as usual.  So it is pretty harmless, except that it is the sort of thing that pretentious pseudo-intellectuals pontificate about to make themselves seem important. One can hear them in person if one has the misfortune to be subjected to them, or one can read their posts online.

It will be interesting to see if Alex K agrees or not.  I am pretty sure he would not word it as brutally as I have.

[Alex K]

Of course as a big disclaimer, I have not been a very important figure in the grand scheme of particle theory, but I would say that I have done some good work and a very decent grasp of the physics and a pretty broad range of expertise. I say that to emphasize that I am not necessarily the gold standard by which to judge expertise in theoretical physics, and to establish that I am not suffering from delusions of grandeur. That being said, I have, just recently, read articles in a respectable journal by professional philosophers concerning my field of study, and have been less than impressed. One guy who is a chair of philosophy of physics, was going on and on about how physicists are misled because how can we possibly advance the field if we don't really know what particles really are and so on. To me it read like someone who doesn't understand the maths desperately trying to tell us that we do not know what we are doing or talking about, because we don't rigidly formulate our theories in a language he understands (because it is arguably impossible). What makes me angry about this is, in his desperate attempt to stay relevant despite not fully understanding the theory, the guy besmirches the reputation of the field. This is not the first time I encountered this kind of lameness. I signed up for the philosophy working group of the german physical society and went to the first meeting, and that was the last one I went to.

There are fortunate examples to the contrary. I know a former colleague of my phd advisor who changed carreers and does intriguing philosophy of physics, addressing questions such as in which sense successive scientific theories improve, and whether they might converge to something that can be called Truth. This guy is good enough to be able to talk about such topics without inducing fatal eyeroll in experts of the field. Not everyone is. You have to have training in some variety of quantum physics, or be really good, not to make a complete ass of yourself when attempting this kind of discussion.

I'd say that people doing philosophy of science professionally without having in depth training in at least one field they address, or better yet research experience, run a high risk of producing work that working scientists perceive as highly embarassing, and there are plenty examples.

Generally,

[JuliaL]

Of course as a big disclaimer, I have not been a very important figure in the grand scheme of particle theory,

---

but I would say that I have done some good work and a very decent grasp of the physics and a pretty broad range of expertise. I say that to emphasize that I am not necessarily the gold standard by which to judge expertise in theoretical physics, and to establish that I am not suffering from delusions of grandeur. That being said, I have, just recently, read articles in a respectable journal by professional philosophers concerning my field of study, and have been less than impressed. He was going on and on about how physicists are misled because how can we possibly advance the field if we don't really know what particles really are and so on. To me it read like someone who doesn't understand the maths desperately trying to tell us that we do not know what we are doing or talking about, because we don't rigidly formulate our theories in a language he understands (because it is arguably impossible). What makes me angry about this is, in his desperate attempt to stay relevant despite not fully understanding the theory, the guy besmirches the reputation of the field. This is not the first time I encountered this kind of lameness. I signed up for the philosophy working group of the german physical society and went to the first meeting, and that was the last one

---

Vell, ve can't all be der virst violinists in der orkestra.
Some ov us gots to push der vind tru der tuba!

After 6 years of medical practice, I thought it might be amusing to take a course in ethics as distribution credits towards an engineering degree.
It was fun, but I wasn't impressed with the rigor.
Math isn't as flexible.  But when it's right it's right.

BTW, is there a 'Particle physics math for dummies?"
I did well in the engineering math courses, though it's been a while.

[Whateverist]

OK, I'm lost already.
But I'll take a shot at demonstrating my ignorance.
Particles trade particles to other particles to make particles or to change particles or to hold particles together against other trades of particles.
But we don't know what a particle is, just how it acts, what it does.
Its sort of particle economics with trades of derivative products which are composite things that don't really exist except for the purpose of trading things to other things on the NYSE to eventually make real things like cash or land ownership.
Sorry, I can't do the math so I have to talk in metaphors.

So in these exchanges, do the 'real' particles know about each other in order to trade 'unreal' particles?
Do they find out about each other by 'fields' (other things whose only evidence of existence is what they do to other things.)
If all these interactions are by exchange of particles, how do the 'real' particles pick which virtual particles to exchange?

[DISCLAIMER=whateverist]Just have to interject to kudos Julia here for a nice piece of lay-quality particle physics theorizing. I'm sure Alex is impressed and more than a little concerned for his job security.][/DISCLAIMER]

So again, you wonder whether or how we can talk about particles without knowing what particles actually are. As I have alluded to earlier, I don't think this is necessarily in the realm of science - but - I also believe that we regularly leave the realm of science when we talk about nature. This is a deep philosophy of science question and I am no philosopher of science, so I can only offer you a half baked cake of my own making. I think the question what particles really are, might possibly not be a valid question. My impression is that we can't help but talk about the objects and goings on in the world in terms of our theories about these objects, and that only in the framework of a theory a multitude of phenomena can be unified into a single object.

So are you saying that even if tables are extremely porous that a case can be made for the existence of dinette sets?

[Alex K]

Of course as a big disclaimer, I have not been a very important figure in the grand scheme of particle theory,

---

but I would say that I have done some good work and a very decent grasp of the physics and a pretty broad range of expertise. I say that to emphasize that I am not necessarily the gold standard by which to judge expertise in theoretical physics, and to establish that I am not suffering from delusions of grandeur. That being said, I have, just recently, read articles in a respectable journal by professional philosophers concerning my field of study, and have been less than impressed. He was going on and on about how physicists are misled because how can we possibly advance the field if we don't really know what particles really are and so on. To me it read like someone who doesn't understand the maths desperately trying to tell us that we do not know what we are doing or talking about, because we don't rigidly formulate our theories in a language he understands (because it is arguably impossible). What makes me angry about this is, in his desperate attempt to stay relevant despite not fully understanding the theory, the guy besmirches the reputation of the field. This is not the first time I encountered this kind of lameness. I signed up for the philosophy working group of the german physical society and went to the first meeting, and that was the last one

---

Vell, ve can't all be der virst violinists in der orkestra.
Some ov us gots to push der vind tru der tuba!

After 6 years of medical practice, I thought it might be amusing to take a course in ethics as distribution credits towards an engineering degree.
It was fun, but I wasn't impressed with the rigor.
Math isn't as poetic.  But when it's right it's right.

BTW, is there a 'Particle physics math for dummies?"
I did well in the engineering math courses, though it's been a while.

I strongly disagree with the idea that math isn't poetic. I find the crystalline elegance with which it describes many things, to be among the most poetic things I know.


Concerning particle maths for dummies, when my field theory text book comes out this fall (which is aimed at advanced undergrad and beginning grad students) I have actually considered doing something like that - kind of a popular science book with extra maths sections.

[Whateverist]

I strongly disagree with the idea that math isn't poetic. I find the crystalline elegance with which it describes many things, to be among the most poetic things I know.

I have always said math a very creative endeavor. If my own maths were up to the task I might have realized "poetic" was the better word. I like that.

[JuliaL]

---

Of course as a big disclaimer, I have not been a very important figure in the grand scheme of particle theory, but I would say that I have done some good work and a very decent grasp of the physics and a pretty broad range of expertise. I say that to emphasize that I am not necessarily the gold standard by which to judge expertise in theoretical physics, and to establish that I am not suffering from delusions of grandeur. That being said, I have, just recently, read articles in a respectable journal by professional philosophers concerning my field of study, and have been less than impressed. He was going on and on about how physicists are misled because how can we possibly advance the field if we don't really know what particles really are and so on. To me it read like someone who doesn't understand the maths desperately trying to tell us that we do not know what we are doing or talking about, because we don't rigidly formulate our theories in a language he understands (because it is arguably impossible). What makes me angry about this is, in his desperate attempt to stay relevant despite not fully understanding the theory, the guy besmirches the reputation of the field. This is not the first time I encountered this kind of lameness. I signed up for the philosophy working group of the german physical society and went to the first meeting, and that was the last one I went to.

---

There are fortunate examples to the contrary. I know a former colleague of my phd advisor who changed carreers and does intriguing philosophy of physics, addressing questions such as in which sense successive scientific theories improve, and whether they might converge to something that can be called Truth.

I'm very keen on the idea that Truth is the property of our knowledge that gives the power to make predictions which turn out.
If your model, mathematical or otherwise, gives accurate predictions, it can be said to be True.
AFAIK, the standard model is the best, most accurate, predictor in existence.  In that sense I'd call it the Truest, unlike the wild guesses about reality as written down by desert nomads.
Now, you just have to overcome chaos when you apply it to larger systems.
Have you gotten past 2 bodies?

I'd say that people doing philosophy of science without having in depth training in at least one field they address, or better yet research experience, run a high risk of producing work that I perceive as highly embarassing.

Yes, embarassing to them.  An empathic response, while honorable, is not necessary.

[Alex K]

Higher number body systems can sometimes be treated in perturbation theory, i.e. a systematic approximation. Newton did not understand this, but Laplace and colleagues did, and this is how they finally were able to fully describe the solar system including the effects planets have on each other.

It is very easy to find scenarios where all analytic description fails and all we can do is try and run a computer simulation, which is also always an approximation.

The equations of motion of the standard model have not been solved exactly analytically either, and need to be treated e.g. with such a perturbation theory.
In fact, Feynman diagrams are exactly that - a graphic representation of a systematic approximation taking more and morr virtual particle effects into account.

But Julia, here's a follow up question to your idea, how do you measure the accuracy of a theory? How accurate is newtonian physics? I can contemplate situations where it fails with arbitrary severity - just go close enough to the speed of light.