Space & Particles: What is the Metric?

[wolram]

It seems the consensus is that space is just a metric, but what is the metric when, we consider (solid) objects, i mean we think of objects as solid, but they are mostly by volume just space, can we say that some un physical stuff constrains particles at some distance apart? or that particles (live) in a metric, without even knowing what this metric is.

 

[Demystifier]

I wonder if anybody understands this question.

 

[malawi_glenn]

No it is a mystery, I don't understand a thing

 

[thenewmans]

OK, fine. I’ll take a crack at it even though I’m a complete amateur. Wolram is a contributor with 3k posts. I haven’t heard of space referred to as a metric. To me a metric is a way of measuring things. So I’ll assume our standard units of measure are suitable for measuring space. Do particles maintain a certain distance from each other? Yes! Look up http://en.wikipedia.org/wiki/Pauli_exclusion_principle" is a great read for that.

Mostly Space
By space I think you mean empty and non-empty contains solid particles with a certain size and mass. But when you get down to that level, that kind of thinking doesn’t work so well. I’ve managed to stop thinking of particles having a size. I don’t even think of them as points. Instead I only think of the forces they have on other particles.

• Particles produce forces.
• Forces control the shape of fields (like space).
• Fields control the movement of particles.

Solid
There’s usually some thermodynamic explanation involved when comparing solids to non-solids. Let’s use a diamond, which is kind of like a really large molecule in that every atom has a covalent bond with its neighbor. You can see through it but you can’t put your finger through it. The bonds in your finger are electromagnetic but not as strong as covalence. When they collide, these bonds don’t break and no bonds are formed between your finger and the diamond. So they stay separated.

Un-Physical
If it has an effect then it’s physical. I think you mean unknown. I’m sure there’s plenty we haven’t learned about all that why there is an exclusion principal at all. But we have testable theories that make very accurate predictions. So that’s a good start.

 

[thenewmans]

When you hear scientists say “Mostly Space” that’s because an atom could be compressed. A neutron star is far more dense. Using that as a "metric", then yes, our atoms are mostly space.

 

[jnorman]

hmmm - it is ALL space. eg, electrons are point particles - they have no volume, they do not take up any space. nucleons are made up of quarks, which are, again, point particles with no volume. photons have no volume. it is fields that permeate space, interactions of which result in all that we see.

 

[thenewmans]

... electrons are point particles ...

I know there are interpretations like that but I don’t know of any testable theories. Are there?

 

[DrChinese]

I know there are interpretations like that but I don’t know of any testable theories. Are there?

The theory is that any fundamental particle, when observed as to position, can be isolated to a volume of space that is arbitrarily small. (You won't see its wave nature at that time.) Experiments confirm this to the limits of current technology. So there is an upper limit on the size of an electron, one which is very small indeed. So experiment is, so far, consistent with theory.

I would agree with the comments that ordinary matter around us, when considered as to its particle nature, is nearly a perfect vacuum. Regardless of how you consider it, all of the matter in the Milky Way at one time was compressed into a volume much smaller than a grain of salt. (Of course it was not organized into atoms at that time.)

 

[wolram]

OK, I haven’t heard of space referred to as a metric. To me a metric is a way of measuring things.

To my mind space is never defined, it is, in cosmology some thing that expands
http://en.wikipedia.org/wiki/Metric_expansion_of_space

Mostly Space
By space I think you mean empty and non-empty contains solid particles with a certain size and mass. But when you get down to that level, that kind of thinking doesn’t work so well. I’ve managed to stop thinking of particles having a size. I don’t even think of them as points. Instead I only think of the forces they have on other particles.

That is fine, i think i understand, but these particles (live) in some thing that is constanly expanding, even though they do not (feel )it

• Particles produce forces.
• Forces control the shape of fields (like space).
• Fields control the movement of particles.

Solid
There’s usually some thermodynamic explanation involved when comparing solids to non-solids. Let’s use a diamond, which is kind of like a really large molecule in that every atom has a covalent bond with its neighbor. You can see through it but you can’t put your finger through it. The bonds in your finger are electromagnetic but not as strong as covalence. When they collide, these bonds don’t break and no bonds are formed between your finger and the diamond. So they stay separated.

I understand that.

Un-Physical
If it has an effect then it’s physical. I think you mean unknown. I’m sure there’s plenty we haven’t learned about all that why there is an exclusion principal at all. But we have testable theories that make very accurate predictions. So that’s a good start.

AFAIK no one has said space is a physical entity lately, so to me it is un physical.
And if particles can be reduced to all most nothing, it seems crazy that i am sitting on a
chair that is all most nothing, and even i am all most nothing.

Thanks for the help.

 

[Dmitry67]

And if particles can be reduced to all most nothing, it seems crazy that i am sitting on a
chair that is all most nothing, and even i am all most nothing.

Thanks for the help.

Particles can repel each other even being pointlike.
In order to interact, they don't need to actually *touch* each other.
So there is nothing strange that you are sitting on a chair made of zero-sized particles

 

[thenewmans]

To my mind space is never defined, it is, in cosmology some thing that expands
http://en.wikipedia.org/wiki/Metric_expansion_of_space

The "Metric expansion of space" does not mean space is a metric. It just means it can be measured. Quote: "The metric expansion of space is the averaged increase of metric (i.e. measured) distance between objects in the universe with time."

AFAIK no one has said space is a physical entity lately, so to me it is un physical.

OK but saying it that way is a little confusing. Un-physical sounds like no physics. And physical entity sounds like it takes up space.

And if particles can be reduced to all most nothing, it seems crazy that i am sitting on a chair that is all most nothing, and even i am all most nothing.

Yeah, I'm with you on that one. But keep in mind, taking up space has a whole different meaning down there at the QM level. To us it's just one thing bumping into another. Down there, it's repelling electromagnetic forces.

 

[debra]

All particles are probably just mathematical models with properties and ways of behaving, but otherwise not the usual small piece of rock or dust as you may believe. How large is a heap of equations and parameters?