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  4. Does a field require a source?
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Does a field require a source?

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Offline opportunity

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Re: Does a field require a source?
« Reply #100 on: 26/02/2018 12:06:12 »
Quote from: Colin2B on 26/02/2018 12:03:52
Quote from: opportunity on 26/02/2018 10:25:34
The field propagates from a source in search of something, right?
Wrong, a field is not searching for anything
Quote from: opportunity on 26/02/2018 11:45:12
Why not say gravity is the failure of every other field force?
Why say it. There is no reason to do so.


So as opposed to a failure there's an "effect"?

Trying not to be esoteric, but, if we're failing to define the source, we have no clue for the outcome......?
« Last Edit: 26/02/2018 12:15:19 by opportunity »
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Offline jeffreyH (OP)

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Re: Does a field require a source?
« Reply #101 on: 26/02/2018 12:42:42 »
Another question to keep things fresh. What is the source of the Higgs field?
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Re: Does a field require a source?
« Reply #102 on: 26/02/2018 12:59:53 »
It's created in theory.....as a (disputed) source one can only consider why. They made it, right?

The point you're making is moot.

Why not ask, "can we see the end of time"? That would be easier than suggesting a field is independent to the cause of it's phenomena. Does a field exist outside of time?
« Last Edit: 27/02/2018 01:47:56 by opportunity »
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Offline geordief

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Re: Does a field require a source?
« Reply #103 on: 26/02/2018 13:45:58 »
Can we say that there is a comprehensive gravity field for the galaxy we are in?

In theory can we model this field in time?

If so can we model it backwards in time?

Can this process be applied to groups of galaxies as they reverse approach the Big Bang as it is theorized?

So is there an uninterrupted dynamic model from that period to "now"?

Is that when fields were first modelable and is  there a  "source"  to be found at that time period?
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Offline Colin2B

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Re: Does a field require a source?
« Reply #104 on: 26/02/2018 15:15:30 »
Quote from: opportunity on 26/02/2018 12:06:12
Trying not to be esoteric, but, if we're failing to define the source, we have no clue for the outcome......?
Is that true?
Consider Newton, he did not find a source for gravity, other than ascribing it to an attraction of masses, but he very accurately described a series of outcomes. Science is the method of observing and then making predictions based on those observations, we don’t necessarily know the root cause.

Let’s go back to my original question to you:
Quote from: Colin2B on 26/02/2018 10:21:43
You said "An electromagentic field propogates of it's own accord in the absence of a source"
Physics says it's the electromagentic wave which propagates.

Could you explain why you think the field propagates.
Your answer doesn't address this question:

Quote from: opportunity on 26/02/2018 12:06:12
The field propagates from a source in search of something, right? Why does a field propagate from an atom? Because it can? This is where "time" becomes bespoke to events in space.
Let me explain why I have a problem with your response.
Take the example of fields which we are very familiar with. Sound waves in air, waves on water. We do not talk about the air pressure, or the water amplitude propagating, nor do we talk about the air or water propagating, we talk about the wave propagating.
OK, these are examples of non-relativistic fields which require a medium, but we apply the same terminology to relativistic fields eg EM field where we have not detected a medium.
So we say that the light wave (quantum = photon) propagates through the em field. That field is a set of measurements of electric and magnetic field strengths.

So a field does not propagate from a source in search of anything.
“Why does a field propagate from an atom? Because it can?” - no, the wave propagates from an atom because an electron changed state and energy was released as an oscillation that we detect as a wave.
“This is where "time" becomes bespoke to events in space.” - haven’t a clue what that means, sounds like pseudoscience or word salad.

In new theories anything goes, but in this section we need to be very clear and precise in what we are saying otherwise we run the risk of creating what (in another thread) you have termed fake news.
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Offline jeffreyH (OP)

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Re: Does a field require a source?
« Reply #105 on: 26/02/2018 17:23:53 »
A little light reading. The Higgs field and the big bang.
https://home.cern/topics/higgs-boson/origins-brout-englert-higgs-mechanism
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Offline Bill S

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Re: Does a field require a source?
« Reply #106 on: 26/02/2018 19:27:21 »
Quote from: Alan
In physics, a field is something that is defined (by a number or a vector) at every point in space. Nothing more, nothing less.

Alan this will probably be sorted out in your response to Lightarrow (#89}, but when you say “a field is something”, I wonder what form that “something” takes. 

Is it a physical thing in which waves/particles propagate, or is it just a measurement?
If it is a measurement, what is the “something” it measures?

There have been times when I have, justifiable, been charged with nit-picking, but such is not the case here, I’m trying to reconcile in my mind two opinions that seem to be incompatible. 

So far, I suspect that "field" may be being used in more than one sense.     
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Re: Does a field require a source?
« Reply #107 on: 26/02/2018 22:10:58 »
Quote from: Colin2B on 26/02/2018 15:15:30
Quote from: opportunity on 26/02/2018 12:06:12
Trying not to be esoteric, but, if we're failing to define the source, we have no clue for the outcome......?
Is that true?
Consider Newton, he did not find a source for gravity, other than ascribing it to an attraction of masses, but he very accurately described a series of outcomes. Science is the method of observing and then making predictions based on those observations, we don’t necessarily know the root cause.

Let’s go back to my original question to you:
Quote from: Colin2B on 26/02/2018 10:21:43
You said "An electromagentic field propogates of it's own accord in the absence of a source"
Physics says it's the electromagentic wave which propagates.

Could you explain why you think the field propagates.
Your answer doesn't address this question:

Quote from: opportunity on 26/02/2018 12:06:12
The field propagates from a source in search of something, right? Why does a field propagate from an atom? Because it can? This is where "time" becomes bespoke to events in space.
Let me explain why I have a problem with your response.
Take the example of fields which we are very familiar with. Sound waves in air, waves on water. We do not talk about the air pressure, or the water amplitude propagating, nor do we talk about the air or water propagating, we talk about the wave propagating.
OK, these are examples of non-relativistic fields which require a medium, but we apply the same terminology to relativistic fields eg EM field where we have not detected a medium.
So we say that the light wave (quantum = photon) propagates through the em field. That field is a set of measurements of electric and magnetic field strengths.

So a field does not propagate from a source in search of anything.
“Why does a field propagate from an atom? Because it can?” - no, the wave propagates from an atom because an electron changed state and energy was released as an oscillation that we detect as a wave.
“This is where "time" becomes bespoke to events in space.” - haven’t a clue what that means, sounds like pseudoscience or word salad.

In new theories anything goes, but in this section we need to be very clear and precise in what we are saying otherwise we run the risk of creating what (in another thread) you have termed fake news.

Colin, I agree with everything you've said according to the arrow of time, the currently accepted model for time and space. Very good.
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Re: Does a field require a source?
« Reply #108 on: 27/02/2018 00:02:48 »
Quote from: opportunity on 26/02/2018 22:10:58
Colin, I agree with everything you've said according to the arrow of time, the currently accepted model for time and space. Very good.
If that arrow ever reverses I’m sure we will be the first to know. Or do I mean last. Or have I got that backwards?  ;)
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Re: Does a field require a source?
« Reply #109 on: 27/02/2018 00:03:57 »
Quote from: Bill S on 26/02/2018 19:27:21
Alan .......when you say “a field is something”, I wonder what form that “something” takes. 

Is it a physical thing in which waves/particles propagate, or is it just a measurement?
If it is a measurement, what is the “something” it measures?
I know Alan gets quite busy, so I’ll put in an interim.
Clearly if you can measure something it is physical.
Take an electric field. The measurement you take (or imagine you take) is of the force (vector) on an infinitesimal test charge at a particular point. That force is real, but take away the test charge and it disappears, and it doesn’t affect a neutral test object. So there is something physical - the force - and we are measuring that force and calling the set of measurements the field. We don’t know what causes the force (other than saying that a charge causes it!) but we can model it and using that model describe how charged particles behave. Clearly, the measurement we took of the force does not cause the force, but it is often convenient to consider the field as a physical object and use shorthand/shortcut terminology like “the field causes the force” or “the field stores energy”. As Matt Strassler will tell you, such thinking shortcuts can be dangerous, we must never forget what lies behind the description.
Simple example. Replace the electric field with a spring. Extend the spring and measure the force for various distances, we have a force field.  As the spring extends it gains potential energy, so we can say the field stores energy, but does it? The spring stores the energy, but the phrase is a convenient shorthand. In the case of a spring reality is obvious, for other fields it might mislead us.

Quote from: jeffreyH on 26/02/2018 17:23:53
A little light reading. The Higgs field and the big bang.
https://home.cern/topics/higgs-boson/origins-brout-englert-higgs-mechanism
Note the terminology - interacting with the field.
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Offline geordief

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Re: Does a field require a source?
« Reply #110 on: 27/02/2018 00:38:45 »
Quote from: jeffreyH on 26/02/2018 17:23:53
A little light reading. The Higgs field and the big bang.
https://home.cern/topics/higgs-boson/origins-brout-englert-higgs-mechanism

All fields I can think of have "local centres."

The gravity field,whilst everywhere is stronger near (to take an example) Black Holes and diminishes further away.

Same with an electron field...

What about this Higgs field?
Does it also wax and wane depending on the environment?

Or is it uniform as I had assumed from what I have heard?
« Last Edit: 27/02/2018 00:41:30 by geordief »
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Re: Does a field require a source?
« Reply #111 on: 27/02/2018 00:44:49 »
Quote from: Colin2B on 27/02/2018 00:02:48
Quote from: opportunity on 26/02/2018 22:10:58
Colin, I agree with everything you've said according to the arrow of time, the currently accepted model for time and space. Very good.
If that arrow ever reverses I’m sure we will be the first to know. Or do I mean last. Or have I got that backwards?  ;)

Haha, nice point, yet time doesn't necessarily have to be reversed if it's not a simple arrow, it could be a type of equation in its own right...,that's another discussion though.
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Re: Does a field require a source?
« Reply #112 on: 28/02/2018 11:45:51 »
Quote from: lightarrow on 19/02/2018 16:05:55
Quote from: geordief on 18/02/2018 23:40:43
Quote from: jeffreyH on 18/02/2018 22:32:55
The energy of a field exists. Otherwise we wouldn't have any forces. It isn't tangible. That does not mean that it is simply an abstract concept.
the field is not just model and  fit for scrap if superseded?
Probably I'll amaze you now, but did you know that an electrostatic field has a mass too?

--
lightarrow
Do you have any reference for that?
How do you measure it?
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Re: Does a field require a source?
« Reply #113 on: 28/02/2018 15:00:13 »
Quote from: Colin
The spring stores the energy, but the phrase is a convenient shorthand. In the case of a spring reality is obvious, for other fields it might mislead us.

The Higgs field comes to mind.  What fills the role of the “spring” in relation to the Higgs field?     
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