Still confused about matter not being solid !

[kevin1981]

Matter is either a solid, liquid or gas. But recently i got told on this board that Atomic "particles" are not solid, so what
are they ?

People say, matter is not solid, so an Electron is not solid. But an Electron exists, however small, so why is it not
solid ? And if it is not solid, what is it ?

[Delvo]

The words "solid", "liquid", and "gas" are descriptions of how large numbers of atoms behave as a group. If the group behaves one way, it's a solid; if the group behaves another way, it's a liquid; if the group behaves another way, it's a gas. Such words can't apply to individual particles because an individual particle can't do what groups of them do.

[cjameshuff]

Stated another way, a bulk material can be solid, liquid, or gas, depending on the strength of the forces between the molecules of the material, the temperature (the amount of energy in random vibrations of those molecules), and the pressure (which packs the molecules in tighter than they otherwise would be and changes the relationship between the first two. They aren't terms that apply to individual atoms or subatomic particles. A particle is a particle, a tiny excitation of quantum fields, and isn't a solid, liquid, or gas.

[Paul Beardsley]

Further to the two replies (which I thought were well put), consider an army, which is made up of soldiers, or a congregation, which is made up of worshippers. A single soldier is not an army; a single worshipper is not a congregation.

It is sometimes convenient, when teaching children, to describe atoms as like tiny billiard balls, or the insides of atoms as miniature solar systems. This is a useful fiction, because it gives people a working idea of what is going on, but it is a fiction. As Richard Feynman put it (heavily paraphrased), you begin with the solar system model of the inside of the atom, then you realise that it is actually more like a cloud, so you work with that idea for a while, then you realise that the cloud analogy isn't true either, and in fact the best analogy is... no analogy, because the inside of the atom does not resemble anything in our experience.

[kevin1981]

Okay thanks. So the solid, liquid and gas states are when there are billions of Atoms together, which make up a material, got it.

I think i know why everything looks solid to us, it is because of the EM forces between Electrons, this is correct yes ?

I know an Electron is described as a one dimensional point particle, with no inner structure. But i am finding it hard to understand why it is not
solid, what is it ?

I am trying to visualize it too, maybe this is a hindrance ?

[Noclevername]

Okay thanks. So the solid, liquid and gas states are when there are billions of Atoms together, which make up a material, got it.

I think i know why everything looks solid to us, it is because of the EM forces between Electrons, this is correct yes ?

I know an Electron is described as a one dimensional point particle, with no inner structure. But i am finding it hard to understand why it is not
solid, what is it ?

I am trying to visualize it too, maybe this is a hindrance ?

It's not a point but a cloud of probable locations. Not really something we can visualize; a lot of quantum physics is that way.

[kevin1981]

It's not a point but a cloud of probable locations

Is that the same with all Atomic particles. I am just trying to understand how matter is not solid at a fundamental level.

[AndreH]

Is that the same with all Atomic particles. I am just trying to understand how matter is not solid at a fundamental level.

I think it would be honest to say we do not know what particles really "are". Even though , as mentioned above it is helpful in some cases to visualize them as small har balls or as cloudes or other helpful analogies. These analogies, referred to as "models" help to understand the behaviour of the particles.
For example the "hard ball" model addinfg some forces between the balls helps to understand the behaviour of gases and there properties.But that does not mean atoms "are" really hard balls.
In fact there is a big part of the scientific community who will tell you we can never know what things really "are, we only can hope to find theories which describe the behaviour and make it possible to predict the outcome of interactions correctly. This is the point were the boundary between physics and phillosophy lies.

Feynman who was quaoted before also said: " I think I can safely say no one understands quantum mechanics"

[kevin1981]

In fact there is a big part of the scientific community who will tell you we can never know what things really "are"

Observer dependance, the only way to really tell would be to look at the universe objectively, but we can not do that. I am learning,
maybe slowly, but i am learning !

Still, anybody else ? How is fundamental matter not actually solid ?

[ravens_cry]

According to this (watch the video, it's fascinating), the reason why matter doesn't clip through each other like a buggy video game is because the electrons of the atoms of one surface repel the electrons in the atoms of the other surface.
Either that, or someone forgot to turn idclip back on.

[AndreH]

Observer dependance, the only way to really tell would be to look at the universe objectively, but we can not do that. I am learning,
maybe slowly, but i am learning !

Still, anybody else ? How is fundamental matter not actually solid ?

Ok, let's pretend for a moment we could know what a particle really "is". What we perceive as solid in normal live is the sum of all forces of one piece of bulk matter (e.g. a wall) when interacting with another piece of bulk matter (e.g. your forehead).
In the microscopic world we also only see the interaction of the forces which we attribute to the particles. So for an electron to "bounce off" from another electron it does not to be solid, it is enough that it interacts via the Coulomb force with the other particle.
As for the question how or by what this force is carried....we are back to the problem of "can we know it at all".

[cjameshuff]

Still, anybody else ? How is fundamental matter not actually solid ?

Solid matter consists of materials where the component molecules are held in fixed positions relative to the neighboring atoms by intermolecular forces, thermal vibrations being insufficient to pull them loose and allow free movement. There isn't anything analogous with individual atoms or subatomic particles, they don't have anything like a solid phase (or a liquid or gas one).

[kevin1981]

So an Electron is an individual piece of sub atomic matter that can be fired one at a time, but it is not solid. I find that unsatisfactory. (Only because if it is not solid, what is it?)

[AndreH]

So an Electron is an individual piece of sub atomic matter that can be fired one at a time, but it is not solid. I find that unsatisfactory. (Only because if it is not solid, what is it?)

Bold mine
so we are back to "we do not know". And yes it is unsatisfactory to me, too. I just learned to live with it

[kevin1981]

[cjameshuff]

So an Electron is an individual piece of sub atomic matter that can be fired one at a time, but it is not solid. I find that unsatisfactory. (Only because if it is not solid, what is it?)

A subatomic particle. That's what it is. "Solid", "liquid", and "gas" are characteristics of large collections of atoms, they are not applicable to individual atoms or subatomic particles. Particles don't have surfaces, yet don't flow like gases. You can't even pin them down to an exact location, and any definition of a specific size is an arbitrary choice for a given purpose, the best you can generally do is the scale of the internal structure, if any. They form interference patterns, they go into bound states with distinct energy levels instead of circling around in continuously variable orbits like planets. Some of them will go right through others, while other combinations interact strongly or annihilate to form more particles. Matter at that scale behaves quite differently, and it's a mistake to try to apply terms that only have meaning at more familiar scales.

Bold mine
so we are back to "we do not know". And yes it is unsatisfactory to me, too. I just learned to live with it

No, "we don't know" is not the answer. It implies that it could be solid, but that we don't know if it is. We do know, it's a particle. We lack common everyday experience with individual particles to give us a firm grasp on their nature, but that doesn't mean we don't know what they are like.

[Shaula]

In poker you can have a wide range of hands. Flush, Straight, Full house being examples of this. Each behaves differently in the game.

Now I take one card from the pack. Is it a flush? A straight? A full house? It is none because those are behaviours/properties of five-card hands. The terms are just not applicable to a single card.

Now swap out the hands for states of matter and card for particle. Do you see what we are saying? Solid, liquid, gas are all ways of describing the way collections of particles behave. They are simply not applicable terms to an individual particle.

[kevin1981]

Do you see what we are saying? Solid, liquid, gas are all ways of describing the way collections of particles behave. They are simply not applicable terms to an individual particle.

Yes, i understand that now and it is very helpful. But i still find it weird that particles are individual but are not solid. It seems there is
no straight forward answer to my question. (I know, quantum mechanics is weird!)

[Delvo]

I think you need to find another word or phrase to describe what you're asking. If you've got it down that a single particle can't literally be an object that's defined as a group of them, then you're apparently expressing an analogy; there's something you expect the two different things to have in common, some way in which you expect them to be similar/comparable, even though they are different in other ways.

In what way would you expect a particle to be at all like a solid? Is it that you picture them as having shapes that don't change? Is it that, when you picture particles colliding, you think of them bouncing off instead of splashing and mixing? Is it that you picture the volume inside them as completely filled, with no gaps? What is it about the traits of solid objects that you expect to find in particles?

[kevin1981]

What is it about the traits of solid objects that you expect to find in particles?

Actually, i think i have been thinking about it a little wrong. The particles themselves do not make up the solid world we see, it is the
electromagnetic forces between electrons. Is that correct?

Though coming back to individual particles, they are real physical entities. I see them as tiny points with no inner structure. If they are
real then they must have a size.

I just can not understand that if they are not solid then what state are they in :/

[kevin1981]

Or is it, simply, they are quantum particles. They are not solid, but we do not know how to describe them
using modern language ?

[Shaula]

We can describe them using modern language and describe them using maths - they are quantum particles. We can describe their properties in terms of probabilities and mathematics very well. What we cannot do is simply translate these properties to something easier to put into more colloquial English. Language just has too many traps and assumptions built in.

You are forgetting that particles are also waves. Something that behaves like a little billiard ball sometimes, like a water wave at other time and like a fuzzy cloud at other - it doesn't behave like any form of bulk matter (Bose Einstein Condensate maybe) we are familiar with.

The particles have the properties which generate the forces that interact to give us a feeling of 'solidity' when we bring two bulk collections of matter together (my hand and the table). You cannot point at one or the other and say "that is solid, that is what makes things solid". Sorry, it is a bit of a brain bender!

[Bobunf]

Humans do not have the brains to visualize atomic and sub-atomic particles. This is not surprising since such an ability would not have contributed to fending off tigers, finding edible fruit or reproducing. Humans also can't visualize four dimensional objects for similar reasons. Humans are able to describe both in mathematical terms, and we find such descriptions extremely useful. Analogues like clouds, waves, particles or hairy balls are not as useful.

Thus, rather than describe a four dimensional hypersphere as a hairy ball, it's more useful to say that the formula for a four dimensional hypersphere is x1^2+x2^2+x3^2+x4^2=r^2. I have no idea what a hypersphere would look like; perhaps no humans do. But from the formula, I can you what it's shadow would look like, what the 3 dimensional volume of its surface would be {(2*pi^2)*r^3}, and lots of other useful stuff. Thinking of it as a hairy ball won't get me very far in answering any questions about it, and a hypersphere is certainly not a hairy ball.

Same thing with electrons. The mathematics can tell us how it will behave. Thinking of it as a cloud, wave, or particle won't.

Give up on the analogues and use the math. Humans just do not have the tools to intuit at an atomic or sub-atomic level.

It would be easier for a blind person who never had sight to intuit about colors. He has the tools for that task, just not the experience.

[PraedSt]

Though coming back to individual particles, they are real physical entities. I see them as tiny points with no inner structure. If they are real then they must have a size.

If you really want to confuse yourself, ask yourself what a string is.

[Jens]

Actually, i think i have been thinking about it a little wrong. The particles themselves do not make up the solid world we see, it is the
electromagnetic forces between electrons. Is that correct?

In a way, yes, because although it's weird to think of this way, we can't really see electrons or protons or any of that stuff. We can only see photons. So our whole image of the world is just a pattern created by how photons strike our eyes.

Another thing, is that although this is not really a good analogy, you can think of the way an airplane's propeller appears to be a solid sphere whereas in reality the propeller blades themselves only occupy a small portion of the what we actually see.

[Paul Beardsley]

Kevin, you've demonstrated how useful it is when someone asks a seemingly simple (but actually quite deep) question, clearly listens to the answers, asks follow-up questions, and so on. This is so refreshing after having sat through several recent threads where someone makes a wrong assertion and then ignores key questions and counter-evidence.

It's also made me rethink the nature of matter, which I found fascinating.

As regards language, I think the problem is that the word "solid" has many figurative meanings. My parents' marriage is as solid as ever; the prosecution have presented a solid case, and so on. Plus it's only natural to think of a proton as like a billiard but smaller, rather than the completely different thing that billiards are made from.

Shaula, I prefer your poker/card analogy to my army/soldier analogy.

[AndreH]

snip.....


No, "we don't know" is not the answer. It implies that it could be solid, but that we don't know if it is. We do know, it's a particle. We lack common everyday experience with individual particles to give us a firm grasp on their nature, but that doesn't mean we don't know what they are like.

bold mine:
this is exactly what I mean by we "don't know". We have a formalism to describe their behaviour, to predict the outcome of experiments and also make use of the predicted properties (Laser would be an example).
If you define this as "knowing what they are" than you are right. My interpretation of the bolded sentence above is "we don't know".

BTW: We don't know does not necesarrily imply they could be "solid". If we know they are not "solid" in the way a wall is solid this is knowing what they not are.
But I said before TMO we crossing the line to phillosophy at this point. (Discussing the "real" nature of things).

[Paul Beardsley]

I wouldn't use the phrase "we don't know" here. What else is there to know besides their behaviour?

[Strange]

Actually, i think i have been thinking about it a little wrong. The particles themselves do not make up the solid world we see, it is the electromagnetic forces between electrons. Is that correct?

I think that is a good mental model for the "solidity" of objects in the every-day world. And, because it is about "the forces between them" it clearly doesn't apply to a single electron.

Though coming back to individual particles, they are real physical entities.

I'm sure there are some who would debate endlessly about the meaning and relevance of the terms "real", "physical" and "entities". Not me though...

If they are real then they must have a size.

Not necessarily. That may be true of macroscopic objects but, as already agreed, the solidity and size of an atom comes about from the forces and other quantum mechanical effects. For example, electrons have to maintain a certain distance from the nucleus (and this distance relates to the energy of the elctron). Also, only two electrons can occupy the same state (energy level). This means that where there are more than two electrons in an atom, they have to be "stacked up" at increasing distances from the nucleus (as Atomic Orbitals). This distribution of electrons is what gives the atom a certain size (which is still rather fuzzy). And then the interactions between atoms is what gives "stuff" its solidity (or liquidity, or gassity).

This all works equally well if you treat the electrons as zero-sized points, as it is the quantum rules and forces which determine their spacing and hence the space occupied by bulk materials.

You might want to google the scanning tunneling microscope, which allows us to "see" individual atoms by interacting with and measuring these forces.

I just can not understand that if they are not solid then what state are they in :/

They are what they are, is the only mental model that works for me. They are not "like" (not even analogous to) anything in our normal experience.

Each particle could be thought of as the collection of properties that define it, brought together in a single point (a consistent set of "deformations" of all the fields involved, perhaps). This relates to the playing card analogy earlier: in the same way that a playing card has properties of suit, color and number, a particle has properties like charge, spin, etc.

[AndreH]

I wouldn't use the phrase "we don't know" here. What else is there to know besides their behaviour?

As I said before this crosses the limit to phillosophy (and also the limit of my ability to express things correctly in English). Just let me try to explain what I mean: "Behavior" is a property attributed to something. It is not the same as that something itself.
So for my personal view we do not know what they "really are". This implies I assume there is a underlying "real nature" of things. We may just not be able to get knowledge about them in principle. As I said we are entering into phillosophy, definitions of words etc. We should not go down that road I believe (or at least maybe not in this thread).
It is just that I personally have never accepted that knowing how something behaves is the same then knowing what it is. I hope I did not confuse kevin1981 too much, because I agree with you this was a positive example how a discussion should work.