Field Question

[Strange]

1 hour ago, MikeAL said:

This is a reflection of how well the charge is able to bend the field. The field is a property of space. If space is expanding and nothing new is entering the universe, than space must surely be diluted out, and thus the field property of space must also be diluted. If not, why not, is my question?

So, as I said before, it sounds like you are talking about the permittivity of space changing as space expands. It might be intuitive or obvious (to you) that this should happen but the evidence suggests otherwise. 

As for the “why”, that is more of a metaphysical question. 

[swansont]

12 hours ago, MikeAL said:

OK, I have no problem with that. And so my question is that if the field is not weakening and yet the universe is expanding, then something seems very wrong with that. I don't think that we can say the fields are simply imaginary mathematical abstractions and thus are not subject to the rules of increasing volume.

The are mathematical abstractions, and you haven't been able to come up with any quantifiable objection. Just this hand-wave about "total force" which AFAIK isn't part of physics.

12 hours ago, MikeAL said:

It is intuitive to think that if a magnet is in a magnetic field generated by W, inside of volume X, and we then keep the field generation by W the same and put it in a larger volume Y, the overall field strength should fall. If the universe is expanding, we can consider its volume expanding from X to Y. We do not however witness a fall in overall field strength. 

I want physics, not intuition. But I'd argue even your intuition is wrong. If you have a box of finite size, the field isn't zero at the boundary. That's a detail you have not been addressing.

12 hours ago, MikeAL said:

You might argue that the field generation is intrinsic to the fabric of the universe and therefore not subject to decay, but as such it should be subject to the fundamental rules of the universe, and because total energy cannot be created nor destroyed but can be converted, should we not ask ourselves what is being converted to sustain the field? It has a bit of a mobius strip feel to it, does it not?

Nothing needs to to be converted to sustain the field. That's another intuitive (and not uncommon) misconception. If a field decayed, then the energy has to go somewhere. Where does it go?

[Strange]

1 hour ago, studiot said:

Everybody glibly says words to the effect

"There is no centre of dilation" for this expansion and the balloon analogy is offered with the statement

There is no centre of expansion for the balloon.

This statement is untrue and hides the fact that

There is no centre of expansion in the manifold that forms the surface of the balloon.

Only if people forget or don’t understand that the analogy is only with the surface of the balloon. The inside of the balloon doesn’t exist in the analogy. 

Someone did suggest that the radius of the balloon could represent time. But I think that is just confusing. 

Edited May 6, 2018 by Strange

[MikeAL]

Just now, swansont said:

The are mathematical abstractions, and you haven't been able to come up with any quantifiable objection.

Did you read my quotes from Hobson?

[swansont]

2 minutes ago, MikeAL said:

Did you read my quotes from Hobson?

Yes.  I think there are subtleties that are missing in his pop-sci explanations.

[MikeAL]

16 minutes ago, Strange said:

As for the “why”, that is more of a metaphysical question. 

No, its a physics question. I don't need to know the spiritual reason why, I was enquiring into what science had to say. If science doesn't know, then it doesn't know. 

18 minutes ago, Strange said:

So, as I said before, it sounds like you are talking about the permittivity of space changing as space expands. It might be intuitive or obvious (to you) that this should happen but the evidence suggests otherwise. 

So, we are all prepared to accept that the permittivity of space does not change even though more of space is mushrooming out all the time and energy cannot be created or destroyed in our universe? That's interesting.

16 minutes ago, swansont said:

The are mathematical abstractions

Swansont is prepared to say that fields do not exist except in mathematics, and that it must be some type of magic that happens when planets orbit the sun? Is that it? Mathematics is a reporting system of events. So it can come up with a theory of why it happens, but its not really true - its just a bedtime story so we can predict when and how weird inexplicable shit is going to happen.

 

[Strange]

1 hour ago, MikeAL said:

If we consider it finite, we have a big bang origin. If we consider it infinite, we still have the space around us expanding.

Just as an aside, the big bang model doesn’t say (or care) if the universe is finite or infinite. 

20 minutes ago, MikeAL said:

So, we are all prepared to accept that the permittivity of space does not change even though more of space is mushrooming out all the time and energy cannot be created or destroyed in our universe? That's interesting.

If that is what the evidence says, yes. 

And I really don’t understand your difficulty with that. 

[StringJunky]

9 minutes ago, MikeAL said:

No, its a physics question. I don't need to know the spiritual reason why, I was enquiring into what science had to say. If science doesn't know, then it doesn't know. 

So, we are all prepared to accept that the permittivity of space does not change even though more of space is mushrooming out all the time and energy cannot be created or destroyed in our universe? That's interesting.

Swansont is prepared to say that fields do not exist except in mathematics, and that it must be some type of magic that happens when planets orbit the sun? Is that it? Mathematics is a reporting system of events. So it can come up with a theory of why it happens, but its not really true - its just a bedtime story so we can predict when and how weird inexplicable shit is going to happen.

 

A field is a geometric description of the distribution of some value in space. It says nothing of the ontological nature i.e. the 'what is', of the phenomena causing the field, so it follows that it is a mathematical abstraction. Science seeks to describe the behaviour of phenomena and objects; what they are of themselves is beyond it's remit. That's why Strange said it's metaphysical.

[geordief]

1 hour ago, StringJunky said:

A field is a geometric description of the distribution of some value in space. It says nothing of the ontological nature i.e. the 'what is', of the phenomena causing the field, so it follows that it is a mathematical abstraction. Science seeks to describe the behaviour of phenomena and objects; what they are of themselves is beyond it's remit. That's why Strange said it's metaphysical.

Is is possible to treat a field as an extensive object (modeled mathematically) so that it is a "body" without boundaries** and with an unlimited number of sources?

 

So ,instead of (or in parallel with) the measurement at any point it can also  be described as a whole?

 

I mean ,the human body (or any system) is sometimes described in terms the whole being greater  than the sum of its parts-and the human body can a further  be treated as a unit in a system .

Is this purely a philosophical question  or is there any scientific merit in viewing a field in this way?

 

By the way re your  " It says nothing of the ontological nature i.e. the 'what is', of the phenomena causing the field, " does not the fact that field only affect objects of the same nature as the source itself say something about the nature of the (particular) field ?  (gravity the exception?)

 

** so "undefined" is a good description

[swansont]

3 hours ago, MikeAL said:

 

Swansont is prepared to say that fields do not exist except in mathematics, and that it must be some type of magic that happens when planets orbit the sun? Is that it? Mathematics is a reporting system of events. So it can come up with a theory of why it happens, but its not really true - its just a bedtime story so we can predict when and how weird inexplicable shit is going to happen.

 

Whoa. That's not what I said, nor is the rest a reasonable extrapolation of what I said., 

3 hours ago, StringJunky said:

A field is a geometric description of the distribution of some value in space. It says nothing of the ontological nature i.e. the 'what is', of the phenomena causing the field, so it follows that it is a mathematical abstraction. Science seeks to describe the behaviour of phenomena and objects; what they are of themselves is beyond it's remit. That's why Strange said it's metaphysical.

This, on the other hand, would be a reasonable summary.

1 hour ago, geordief said:

By the way re your  " It says nothing of the ontological nature i.e. the 'what is', of the phenomena causing the field, " does not the fact that field only affect objects of the same nature as the source itself say something about the nature of the (particular) field ?  (gravity the exception?)

If I know the field some point, I don't know if it's due to some charge ay some distance, or a different charge at a different distance.

Plus, it tells us nothing about why the field exists in the first place. Physics models behavior, and fields are a way of quantifying the behavior.

[Strange]

1 hour ago, geordief said:

does not the fact that field only affect objects of the same nature as the source itself say something about the nature of the (particular) field ? 

Not really because the field is invented to describe exactly that sort of affect. 

[geordief]

9 minutes ago, swansont said:

 

(1)If I know the field some point, I don't know if it's due to some charge ay some distance, or a different charge at a different distance.

(2)Plus, it tells us nothing about why the field exists in the first place. Physics models behavior, and fields are a way of quantifying the behavior.

(1) Because both those charges (if they exist) are field originators  whose fields are (as you say) indistinguishable.

Extrapolating ,there is only one field made up of all the "component"  fields.

(2) Doesn't the charge create a field -and vice versa? If we don't try to understand the ontology of a particle (apart from its make up) why would we try to understand the ontology of a field ?

 

But the field is every bit as "real" as what we used to think of as particles ,isn't it?

The particle is dead ,long live ....the particle?  

8 minutes ago, Strange said:

Not really because the field is invented to describe exactly that sort of affect. 

So that just tells us what kind of a field it is..... 

 

"effect" for your English lesson

[studiot]

6 hours ago, MikeAL said:

So, we are all prepared to accept that the permittivity of space does not change even though more of space is mushrooming out all the time and energy cannot be created or destroyed in our universe? That's interesting.

Why would it change?

Would that not imply this additional space is different from the previous space.

So what is your proposal for phenomena that cross the boundary between the old space and the new space?

5 hours ago, StringJunky said:

A field is a geometric description of the distribution of some value in space. It says nothing of the ontological nature i.e. the 'what is', of the phenomena causing the field, so it follows that it is a mathematical abstraction. Science seeks to describe the behaviour of phenomena and objects; what they are of themselves is beyond it's remit. That's why Strange said it's metaphysical.

 

2 hours ago, swansont said:

This, on the other hand, would be a reasonable summary.

 

Well I think it good enough to give +1 to.

SJ has effectively put forward the Physics definition of a Field.

Far better than the sort of Field the OP seems to envisage as some sort of web spun out by spiderman.

2 hours ago, geordief said:

But the field is every bit as "real" as what we used to think of as particles ,isn't it?

Please, please get hold of a copy of "The Lighness of Being" by Nobel physicist Frank Wilczek.

He dedicates this book to developing this sort of Field and the idea that 'particles' are disturbances of it.

 

6 hours ago, Strange said:

Only if people forget or don’t understand that the analogy is only with the surface of the balloon. The inside of the balloon doesn’t exist in the analogy. 

Someone did suggest that the radius of the balloon could represent time. But I think that is just confusing. 

Please tell me how the balloon could exist or expand without the third dimension?

Perhaps not time itself, but Minkowski ct, which would be a length and therefore accaptable as a measure of radius.
Do you have a reference, If so I would be very interested.

The diagram of this is what I was considering for geordie.

Still thinking about this, my trip up Crook Peak offered wonderful clarity.

Edited May 6, 2018 by studiot

[Strange]

7 minutes ago, studiot said:

Please tell me how the balloon could exist or expand without the third dimension?

It’s an analogy. Not a balloon. 

[StringJunky]

2 minutes ago, Strange said:

It’s an analogy. Not a balloon. 

It's 2D curved plane in a 3D container.  

[studiot]

16 minutes ago, Strange said:

It’s an analogy. Not a balloon. 

Ok smartypants, how would the analogy be possible if the surface of the balloon was not curved in the third dimension?

Edited May 6, 2018 by studiot

[Strange]

2 minutes ago, StringJunky said:

It's 2D curved plane in a 3D container.  

Ideally, one would ignore the third dimension as we are talking intrinsic curvature

 

14 minutes ago, studiot said:

Ok smartypants, how would the analogy be possible if the surface of the balloon was not curved in the third dimension?

See above ...

[Janus]

8 minutes ago, studiot said:

Ok smartypants, how would the analogy be possible if the surface of the balloon was not curved in the third dimension?

By using non-Euclidean geometry.    The balloon analogy is a tool that's designed to simulate non-Euclidean geometry in a way that is easily visualized,  by imagining what it would be like to try to perform Euclidean plane geometry on the surface of a sphere.    In true non-Euclidean  plane geometry,  there is no 3rd dimension that the plane curves in, but the rules of geometry differ from Euclidean geometry, (the interior angles of  triangle don't add up to 180° etc.)    In the same way, the behavior of non-Euclidean 3 dimensional space simulates that of 3-d space curved through a 4 spacial dimension, but without the actual existence of a 4th spacial dimension.

[Strange]

Yeah. That’s exactly what I would have said if I weren’t on my phone...

[StringJunky]

19 minutes ago, Strange said:

Ideally, one would ignore the third dimension as we are talking intrinsic curvature

 

See above ...

Would a 2D inhabitant on its surface be aware it was curved? Yes,  I do understand the 3D aspect is superfluous in that analogy.

Edited May 6, 2018 by StringJunky

[Strange]

3 minutes ago, StringJunky said:

Would a 2D inhabitant on its surface be aware it was curved?

Yes... Janus (as always) answered this far better than I could ... eg. angles of a triangle. Which is, basically, how we know the universe is, overall, flat. 

Edited May 6, 2018 by Strange

[beecee]

9 hours ago, studiot said:

But charge may 'bend' a field, but it can't bend space.

Some varied and interesting answers here.....https://www.researchgate.net/post/Is_the_electric_field_real_or_only_a_theory

9 hours ago, studiot said:

Mass, by way of gravity 'bends' space.

I don't like that. Mass bends spacetime [changes the geometry]  and we see that reflected as gravity. Gravity/spacetime are one and the same.

Quote

Do you consider space to be finite or infinite?

 

8 hours ago, MikeAL said:

If we consider it finite, we have a big bang origin. If we consider it infinite, we still have the space around us expanding. Either way we get a dilution effect. 

Not exactly...The BB simply applies to the observable universe. The BB can also accommodate an infinite  universe. http://www.astro.ucla.edu/~wright/infpoint.html

8 hours ago, MikeAL said:

Gravity is certainly the curvature of spacetime as it relates to mass, but I'm not sure if we can say that charge doesn't bend space in some other way.

I tend to agree.

Edited May 6, 2018 by beecee

[Strange]

4 hours ago, geordief said:

"effect" for your English lesson

You know, I did think about that, for quite a long time, and decided that, in this context, "affect" (which is the topic of discussion) was OK. But, you know ... language...

[beecee]

10 hours ago, MikeAL said:

An electric field at rest has the ability to exert forces on electrically charged objects and thus do work on them; such ability to do work is precisely what we mean by energy. Mass-energy equivalence then implies that EM fields at rest have mass, implying that, like Johnson’s stone, they resist acceleration and they have weight. … If you could accumulate sufficient EM field within an enclosed region, you could kick it. P88

Fields are properties of space itself. P77

Although we can’t see these fields directly, we’ll find they are physically real and not just something scientists invent to concoct theories and make calculations. P77-78

 

Contemplating this, one must wonder why with the expansion of the universe the value of the field does not change, particularly when we consider that energy is neither created nor destroyed, but simply transformed.

 

That's great. So my question is why is it not weakening?

I'm not sure what you mean by this. Can you elaborate?

Not only energy, but also mass resides in the so-called empty space between the two separated magnets. This space isn’t really empty after all! It has weight, just like a rock. But the EM field energy does not have a significant effect on the mass of ordinary matter, because ordinary matter is made of atoms and the EMP field energy is millions of times smaller than the total energy of the atom. P89-90

The result of this theoretical calculation was that fully 95% of the mass of the protons and neutrons comes from the energy of their strong force fields! This is our best estimate of the mass of these fields! ...The mass of the universes ordinary matter comes not from so-called “solid” objects but almost entirely from force fields! P90-91

An interesting answer here.....https://www.researchgate.net/post/Is_the_electric_field_real_or_only_a_theory

extract:

Quote

For me, the fact that photons can be detected at least as readily as charged particles (and much more readily than neutrinos) is sufficient to establish their reality. I certainly accept the fact that opinions on what it all means vary widely among physicists, and it is interesting that classical physics is enough to raise such questions. I was most surprised by Dyson's stance, since local quantum field theory did more than anything (short of supersymmetry, which remains to be seen) to place matter and gauge fields on comparable footing. I assume the objections raised about the reality of electromagnetic fields must apply to the other gauge fields as well, for similar reasons, but an interesting followup question might be - is the Higgs field real? (I would say yes.)

I don't like your continued referencing as to the field weakening with expansion, rather, I prefer as I said before, spacetime is getting less dense.

Edited May 6, 2018 by beecee

[Strange]

9 hours ago, MikeAL said:

Gravity is certainly the curvature of spacetime as it relates to mass, but I'm not sure if we can say that charge doesn't bend space in some other way.

Maxwell's equations can be described in purely geometric terms. Kaluza-Klein theory was the first attempt to combine GR and EM in a single (geometric) model. Perhaps not surprisingly, it requires 5 dimensions because the "things" being curved by mass and by charge are not the same. (Which is yet another reason why I don't think these models describe "reality" but just the way it behaves.)

Edited May 6, 2018 by Strange