Elementary particles and randomness

[Brunolem33]

From the elementary particles that science has been able to identify until now, are there any that appear to be useless, at least as far as we know?
Or do all the identified particles play a role in the grand scheme of the universe?

 

[Orodruin]

What do you mean by "useless"? Particles do not have an underlying "purpose" in physical theories. They are introduced because they are needed to provide a good description of how nature works. Asking if there is a "grand scheme" is a religious and philosophical question rather than a physics question.

 

[Brunolem33]

What do you mean by "useless"? Particles do not have an underlying "purpose" in physical theories. They are introduced because they are needed to provide a good description of how nature works. Asking if there is a "grand scheme" is a religious and philosophical question rather than a physics question.

What do you mean by "they are introduced"?
I thought that these particles were actually tangible and had been discovered by means of scientific research, not that they were a theorerical creation for practical purposes.
"Grand scheme" may not be the right term.
What I mean, for example, is that we have the quarks and the electron, and that together these particles form atoms.
Or there is the photon which carries the electromagnetic force.
Now, are there other particles that science has been able to identify, but to which it was not able to assign a role?
In other words and as far as we know, the universe would remain the same if these "unassigned" particles didn't exist.

 

[Orodruin]

Physics (and science in general) is about creating a model which describes observations, nothing else. We introduce concepts such as energy, particles, and waves because it gives a good description of what we can observe. If you want to say that these concepts are "real" in any sense of the word, you are leaning more to the philosophical than to the physical side of things.

What I mean, for example, is that we have the quarks and the electron, and that together these particles form atoms.

This is not true. There is no deeper meaning in quarks and electrons forming atoms and it is not their "purpose" to do so. They have properties which make them do that, which in turn makes them a good description of observations.

Or there is the photon which carries the electromagnetic force.

And here you are ore-supposing that there is an electromagnetic force. The implication is in the other direction, photons are introduced because they give a good description of observations, among them the emergence of the electromagnetic forces. There is no deep purpose in the existence of the EM force, it is just a good description of observations.

Now, are there other particles that science has been able to identify, but to which it was not able to assign a role?

Again, this is the wrong question to ask. Any concept in physics simply would not be there if it was not to describe observations, if nothing else the observation of the particles themselves. Physics is not about assigning meaning.

In other words and as far as we know, the universe would remain the same if these "unassigned" particles didn't exist.

By definition no. A universe where they did not exist would be intrinsically different simply by the fact that it does not have the same particle content.

 

[Brunolem33]

Physics (and science in general) is about creating a model which describes observations, nothing else. We introduce concepts such as energy, particles, and waves because it gives a good description of what we can observe. If you want to say that these concepts are "real" in any sense of the word, you are leaning more to the philosophical than to the physical side of things.This is not true. There is no deeper meaning in quarks and electrons forming atoms and it is not their "purpose" to do so. They have properties which make them do that, which in turn makes them a good description of observations.And here you are ore-supposing that there is an electromagnetic force. The implication is in the other direction, photons are introduced because they give a good description of observations, among them the emergence of the electromagnetic forces. There is no deep purpose in the existence of the EM force, it is just a good description of observations.Again, this is the wrong question to ask. Any concept in physics simply would not be there if it was not to describe observations, if nothing else the observation of the particles themselves. Physics is not about assigning meaning.By definition no. A universe where they did not exist would be intrinsically different simply by the fact that it does not have the same particle content.

I am not sure I understand all this.
How can particles be only some kind of concept if we can actually manipulate them and get something out of these manipulations?
For example, scientists use photons, or at least a particle they call photon, in order to perform the double slit experiment.
For example, we use electrons to produce electricity, which in turn produces something else, and so on.
These are not observations, but actions based on the results of former observations.

 

[mfb]

How can particles be only some kind of concept if we can actually manipulate them and get something out of these manipulations?

We can manipulate things and we call some of those things particles. For other things, we say "they are made out of particles". That is our description. It is possible to find different descriptions for the same observations.

The description of the regular double-slit experiment is much easier with a model without photons - with waves.

 

[rootone]

From the elementary particles that science has been able to identify until now, are there any that appear to be useless, at least as far as we know?
Or do all the identified particles play a role in the grand scheme of the universe?

A particle which does not interact at all with anything else in any way would be completely unobservable.
A description of such a particle can't be a part of physics, since physically such a particle is a non-entity.

 

[newjerseyrunner]

A particle which does not interact at all with anything else in any way would be completely unobservable.

Not totally true, you can observe them indirectly in particle accelerators. A stable particle that does not interact with anything well be detectable as a collision of two protons that produce seemingly nothing as a result, or a slew of particles who's energy doesn't add up to the original amount of energy. An unstable particle would also be detectable after it decays, you'd see a a spray of particles seemingly coming out of nothing.

 

[rootone]

Not totally true, you can observe them indirectly in particle accelerators. A stable particle that does not interact with anything well be detectable as a collision of two protons that produce seemingly nothing as a result, or a slew of particles who's energy doesn't add up to the original amount of energy. An unstable particle would also be detectable after it decays, you'd see a a spray of particles seemingly coming out of nothing.

I agree with that, what I meant was that proposing a particle which has no effect on anything, not even indirectly, is meaningless,
since as far as physics is concerned it makes no difference whether it exist or not.
(A bit like adding the term '+0' to the end of a math formula)

 

[newjerseyrunner]

I agree with that, what I meant was that proposing a particle which has no effect on anything, not even indirectly, is meaningless,
since as far as physics is concerned it makes no difference whether it exist or not.
(A bit like adding the term '+0' to the end of a math formula)

Sometimes "particles" come out of math that aren't real things. Spinon for example, I tend to think of the most elementary particles more of abstract concepts than actual things. Yes, a particle with absolutely no interactions, no structure, or energy, is perfectly valid as far as I know. You can always add zero or multiply by one.

 

[Orodruin]

Not totally true, you can observe them indirectly in particle accelerators.

How are you planning to produce a particle which does not interact at all in a particle accelerator?

A stable particle that does not interact with anything well be detectable as a collision of two protons that produce seemingly nothing as a result

No it will not, because it will never be produced in a proton-proton collision. If it does not have any interactions at all, in particular it does not have any interactions with the proton constituents. There is a difference between "very weak" and "non-existent".

 

[newjerseyrunner]

How are you planning to produce a particle which does not interact at all in a particle accelerator?No it will not, because it will never be produced in a proton-proton collision. If it does not have any interactions at all, in particular it does not have any interactions with the proton constituents. There is a difference between "very weak" and "non-existent".

Agreed, I retract my posts.

 

[Brunolem33]

I agree with that, what I meant was that proposing a particle which has no effect on anything, not even indirectly, is meaningless,
since as far as physics is concerned it makes no difference whether it exist or not.
(A bit like adding the term '+0' to the end of a math formula)

Backing my initial question was something else.
As far as I understand, elementary particles appeared sometime after the BB, from the cooling plasma that was there.
If these particles were created randomly, which was supposedly the case, there must have been millions upon millions of different kinds of particles created, out of which only a tiny number interact and have thus revealed themselves to us.
It seems to be the way things work in the universe, whatever the scale: random creation of a very large number of something, out of which only a very small number happens to be useful.

 

[mfb]

If these particles were created randomly, which was supposedly the case, there must have been millions upon millions of different kinds of particles created

Why should there be millions of different kinds of particles?

 

[Brunolem33]

Why should there be millions of different kinds of particles?

Because if that was not the case, one could wonder about randomness when it comes to the creation of the universe.
If only the particles that interact and that we have been able to observe existed, that would be an extraordinary coincidence.
To make a comparison, imagine that instead of the initial plasma, there was a sea of molten plastic which, after cooling, formed blocks of Lego.
Wouldn't it be incredible if all these randomly created blocks could be used to build, say, a toy car, without any block left on the side because unable to fit in the car?
In fact, we might expect that only a tiny number of blocks could be used to build the car and that millions of others, with different shapes and sizes would be of no use for this purpose.
The same could be true for particles.
Out of a very large number of available particles, only a few would fit in the building of the universe.

 

[Vanadium 50]

I think this is somewhere between "philosophy" and "wrong". Can we maybe restrict the discussion to what can be addressed by the scientific method?

 

[rootone]

... would be of no use for this purpose ...

Purpose implies intention ... by whom? ...

 

[Brunolem33]

I think this is somewhere between "philosophy" and "wrong". Can we maybe restrict the discussion to what can be addressed by the scientific method?

I don't see the philosophical aspects in suggesting that there could be much more kinds of particles than those already observed?
Having said that, could you explain why this suggestion is wrong?
It certainly could be wrong but I'd like to know the arguments.

 

[Brunolem33]

Purpose implies intention ... by whom? ...

Maybe I used the wrong word...what about replacing it with creation?

 

[rootone]

Ah, well there are some reasonable theories of the existence of particles beyond those which are known and are part of the standard model.
However these predict the possibility of particles, or objects, which DO interact one way or another with the known ones, or are components of them.
String theory, Supersymmetry.

 

[Brunolem33]

Ah, well there do exist reasonable theories of the existence of particles beyond those which are known and are part of the standard model.
However these predict the possibility of particles, or objects, which DO interact one way or another with the known ones, or are components of them.
String theory, Supersymmetry.

What about dark matter?
Could it be made from non yet observed particles?
Does it interact with other known objects?

 

[rootone]

https://en.wikipedia.org/wiki/Weakly_interacting_massive_particles

 

[Vanadium 50]

I don't see the philosophical aspects in suggesting that there could be much more kinds of particles than those already observed?

1. You are ascribing purpose.
   
2. You are claiming millions of kinds of unobserved particles with no evidence. Why not one or two?

 

[Brunolem33]

https://en.wikipedia.org/wiki/Weakly_interacting_massive_particles

Thanks.

 

[Brunolem33]

1. You are ascribing purpose.
   
2. You are claiming millions of kinds of unobserved particles with no evidence. Why not one or two?

I already answered the question about purpose previously, and offered to replace this word with creation.
Why so many kinds of particles?
Because of randomness.
What would be the odds of a cooling plasma randomly giving birth to a small number of kinds of particles, all of them fitting in the creation of our universe?
To make a comparison, what would be the odds of having a universe limited to the solar system, conveniently harboring the Earth and life?.
Since solar systems and their planets are created randomly, it seems much more likely to get an Earth like planet out of billions of planets rather than out of a handful.
Thus, in the same way that countless planets have been created for nothing, as far as life is concerned, countless kinds of particles could have been created for nothing, as far as building the universe is concerned.

 

[rootone]

What would be the odds of a cooling plasma randomly giving birth to a small number of kinds of particles, all of them fitting in the creation of our universe?

Well the odds are better than zero, since 'our' Universe exists.
In some interpretations of QM there *could be* other universes, 'our' Universe being part of a bigger picture.
I am not personally a fan of that idea.

 

[Orodruin]

Because of randomness.

You cannot just quote randomness. It is not a valid reference. The randomness that appears in for example quantum mechanics still has rules to it. So does the creation of particles in the early Universe. When physicist propose particle candidates for dark matter they must in fact be very careful in providing a mechanism through which it can be created in the early Universe. What you seem to be talking about is not randomness but complete and utter chaos.

 

[rootone]

I think it could be that you are looking for 'Intelligent design', another meme for 'God/Allah' .. etc.
That isn't science, it's mysticism, and it explains nothing (except irrational behaviour of some people)

 

[Brunolem33]

I think it could be that you are looking for 'Intelligent design', another meme for 'God/Allah' .. etc.
That isn't science, it's mysticism, and it explains nothing (except irrational behaviour of some people)

Actually randomness, or rather chance (see reply above), is quite the opposite of design, intelligent or not.
If there is intelligent design, why bother with infinity, with countless galaxies and planets, why not have our solar system only and be done with it?
What bothers me regarding particles is that all those that have been discovered play a role, or fit, in building the universe.
This seems too good to be true, too "creationist" if you prefer.
Chance should have led to the creation of countless kinds of particles, out of which many would have end up having no use in the building the universe.

 

[Brunolem33]

You cannot just quote randomness. It is not a valid reference. The randomness that appears in for example quantum mechanics still has rules to it. So does the creation of particles in the early Universe. When physicist propose particle candidates for dark matter they must in fact be very careful in providing a mechanism through which it can be created in the early Universe. What you seem to be talking about is not randomness but complete and utter chaos.

Thank you for correcting my vocabulary (being French and not a physicist doesn't help, but is no excuse for not paying attention).
Maybe the word chance would be more appropriate.

 

[Orodruin]

Thank you for correcting my vocabulary (being French and not a physicist doesn't help, but is no excuse for not paying attention).
Maybe the word chance would be more appropriate.

No, it would not be. The aim of physics and other natural sciences is to describe observations and make predictions based on the models. What you are describing is simply not scientific. You simply cannot make blanket statements without a proper description to back it up.

 

[Brunolem33]

No, it would not be. The aim of physics and other natural sciences is to describe observations and make predictions based on the models. What you are describing is simply not scientific. You simply cannot make blanket statements without a proper description to back it up.

I am not making any statement.
I am not saying that there are countless kinds of particles.
I am merely saying that, if particles were created by chance, maybe more, or even much more, than those already observed were created
More generally, after the few days I have spent since I joined this forum, I am a bit surprised by how restrictive it is.
Science appears to be used as a straitjacket in order to limit the exchange of ideas.
I understand that discussions must be kept within boundaries, but if the forum repels, willingly or not, those who don't talk the talk and walk the walk, it becomes only a vast congress for physicists, out of which innovation and new ideas are unlikely to pop up.

 

[ChrisVer]

Simply put: the particles we have might seem to fit in the scheme to you, but it's the other way around. As discussed a particle which doesn't interact at all will never be put in the particle content because it cannot affect what you're observing. Some particles were predicted by theory, but that's because the model we had at hand was the 'best' so far (or it survived because of it).
I don't get the randomness thing... If I close you in a room and give you 1000 m&m you can start shooting them inside the room but they will be randomly around you... or the same with the dice- what you bring is random but the final outcomes are fixed by the type of the die. If Nature has 40particles in total (if that makes sense), the final results would have been 40.

 

[Brunolem33]

U

Simply put: the particles we have might seem to fit in the scheme to you, but it's the other way around. As discussed a particle which doesn't interact at all will never be put in the particle content because it cannot affect what you're observing. Some particles were predicted by theory, but that's because the model we had at hand was the 'best' so far (or it survived because of it).
I don't get the randomness thing... If I close you in a room and give you 1000 m&m you can start shooting them inside the room but they will be randomly around you... or the same with the dice- what you bring is random but the final outcomes are fixed by the type of the die. If Nature has 40particles in total (if that makes sense), the final results would have been 40.[/QUOT
Refering to your m n' m exemple, let's imagine that there is a vast expanse of very hot melted chocolate which is cooling.
While cooling the chocolate forms little blobs of different shapes and sizes.
What are the odds that, at the end of the cooling process, all the chocolate blobs (= particles) created can be used to make an Easter egg (= universe)?
Isn't it more likely that a great number of these blobs will remain on the side, useless for the Easter egg, as leftovers from the creation process?

 

[Orodruin]

I am merely saying that, if particles were created by chance, maybe more, or even much more, than those already observed were created

I think you need to understand what "elementary" in "elementary particle" means. It means that it is the smallest type of building block available in our models and there is most likely not an infinite set of different types of those.

More generally, after the few days I have spent since I joined this forum, I am a bit surprised by how restrictive it is.

It may appear restrictive to you because we are actually being scientific and we are not open to personal speculation. Many personal theories are easily shot down simply by the fact that they contradict observations already made. People at this forum do not have the time nor the will to spend their time here shooting down personal theories and Physics Forums is not intended for that reason. It is intended for the teaching and discussion of mainstream science as it is currently understood. There are several channels through which actual science is being done and communicated and it is not the aim of Physics Forums to be one of those.
Many of the restrictions you will encounter are simply based on this. Physics, and science is general, is very restrictive because it is an empirical science which has to describe experiments properly.

There is also one thing which is strictly worse than being wrong in science, and it is being right regardless of the experimental outcome. A theory which would be fine regardless of what observations you make is not falsifiable and therefore a bad theory. Saying that everything is random and happens by chance is essentially such a statement.

Science appears to be used as a straitjacket in order to limit the exchange of ideas.

There are several ways that professional scientists exchange ideas. Physics Forums is not and does not strive to be one of those. And as I also just said, ideas which are simply wrong or vacuous are naturally disregarded. Statements which cannot be falsified are not the domain of science, but pure philosophy.

I understand that discussions must be kept within boundaries, but if the forum repels, willingly or not, those who don't talk the talk and walk the walk, it becomes only a vast congress for physicians, out of which innovation and new ideas are unlikely to pop up.

Good, that is how it is supposed to be. Physics Forum is not intended for the development of science.

Also, a physician is a medical doctor.

 

[ChrisVer]

U

The thing is then that you say that the particle content should be randomly chosen (why would that make any sense?). However I am saying that you had a fixed number of particles: the ones we know and Dark Matter, and those were produced at some point... Now the total number of different particles is unknown I guess, and it depends on the model you choose as a higher energy than the standard model theory. For example in SUSY you have at least double particle types... for an SU(2)xSU(2) breaking to the SM one you have additional gauge bosons: Wprimes and Zprime etc...

 

[mfb]

@Brunolem33: You got the time ordering wrong. Those particles are not created by a plasma, the are making up the plasma.
In the molten lego analogy: all that molten lego is made out of protons, neutrons and electrons. Cooling it can give various pieces of different shape, but those pieces are all not elementary particles.

In more physical terms, our universe is described as spacetime with various fields in it. The electromagnetic field is one, but there is also an "electron/positron field", a "muon/antimuon field" and so on. One field for one particle type (ignoring some technical details here). The number of fields is fixed, we live in a universe with a specific set of those. We found some of them. We probably did not find all (because dark matter is still a mystery and a few other questions are still open), but there is no indication that we would have missed millions of them.