Science a GoGo's Home Page Forums General Discussion Physics Forum Mass & Velocity

how does the magnet know?

you science cult religion tells the magnet exactly
when to start moving , the reason your fundamentalist cult religion members cant figure these simple things are because
your diverse religions conflict with each other.

your so pitiful orac that your religious cult fundamentalist
nature is showing through the seams of your skirt.
you wacko , if you would just take a little time and examine
your fake science cults you would find that what I say is true.

how was that?
pretty good troll ay?

you hoser

My line of thought was that moving A would cause a ripple in the field which would move from A to B at "c".



Ripples, particles, virtual particles - they have a tendency to run together

Presumably, because science differs from dogma, different scientists can hold different views. No doubt that's good for science, but it can be a bit confusing for us non-scientists.

I think I'm going to have to come back to the particle/virtual particle distinction later.

This is what is so confusing to people who haven't had the chance to make an in depth study of QM. There are a lot of ways to express it, and if you start out studying one way you can get confused when somebody says it in a different way. The results that you get if you follow one method of expression are pretty much the same as the other, but it can kind of blow your mind. It does take a lot of study to really follow something when it is being discussed from the different view points. And if you don't understand the math that leads to the view points it really gets complicated.

Bill Gill

I suppose the only positive thing that can be said about confusion is that as long as you patiently pick away at it, it can result is some reasonably satisfying conclusions.

One of the most understandable (brief) accounts of the difference between a particle and a virtual particle that I have found is from Matt Stassler:

"The best way to approach this concept, I believe, is to forget you ever saw the word “particle” in the term. A virtual particle is not a particle at all. It refers precisely to a disturbance in a field that is not a particle. A particle is a nice, regular ripple in a field, one that can travel smoothly and effortlessly through space, like a clear tone of a bell moving through the air. A “virtual particle”, generally, is a disturbance in a field that will never be found on its own, but instead is something that is caused by the presence of other particles, often of other fields."

I suspect that Orac will argue with that, but that's where the interest comes in. Given enough time and patience, even I may eventually have some idea what it's all about.

Bill.S before we even bother discussing particles there is a problem you must decide what a field is?

Much of what goes wrong and confusing with physics is in the teaching and Matt is confusing you because he is taking you into the problem the wrong way in my view.

Go back to what Matt Strassler said



That is a classic physics avoid the question it's an answer Tutor Turtle would have been proud of because first it tells you nothing and the only things it does say are wild assumptions

Lets break it down claim by claim

1.) A field is something that is present everywhere in space and time .... Proof?

There are obvious problems with this statement a farady cage was invented in 1836

http://en.wikipedia.org/wiki/Faraday_cage => Such an enclosure blocks external static and non-static electric fields.

Things can block fields but isn't it in all space and time ???????

Quantum mechanics causes this statement even more issues

http://www.popsci.com.au/science/researc...-the-first-time

That macroscopic teleportation included the fields because thats how they monitored they were successful.



2.) A field is something that zero or not zero, and can have waves in it.

This statement is weird especially for a physicist. I mean we have electromagnetic waves already which involves the fields



From what he is saying now the fields have waves in them?????


3.) A field is something that if it is a quantum field, its waves are made from particles.

What so a quantum field is different from other fields???????


To me all Matt has done is confused everything into a right royal mess.


Then your second post he is starting to get warmer to how to go into the problem



I agree I would like to get rid of the word particle.

Problems left:

1.) What is a field still no clue????
2.) How can you have a ripple in a field because we havent defined a field.

The rest will then work.

Faraday cages cannot block static and slowly varying magnetic fields, such as the Earth's magnetic field
(a compass will still work inside).

you may be able to shield the insides of a box to a degree
but as long as there are particles inside the box there will
always be a field inside the box.

does that sound right?

how does light travel at the speed of light?

So can I attempt a different way into the problem for you, so lets start with question 1.

1.) What is a field.

At it's most basic a field is the amount of energy per unit volume across an area of spacetime.

All fields we thus define

Field = Energy/Volume

Hence a field can only go to zero and be non existant in the absence of energy

This can be shown to be true by all the known fields

Electric and Magnetic
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/engfie.html

Gravity
http://en.wikipedia.org/wiki/Gravitational_field

Lets use the GR form as science believes it is more accurate



Here T is the stress–energy tensor, G is the Einstein tensor, and c is the speed of light.

The Einstein tensor and the speed of light are constants so you can only have zero gravity by taking the energy-stress tensor value T to zero. That is there is no energy in the unit area of space to create tension.


So while we havent yet described the structure of a field we have got one important fact and understanding of a field and that is whenever you see a field you are seeing energy in a given volume of spacetime.

It is one of the most important understanding of fields and one of the very basic facts on fields that can not be disputed.
Yet it is all too often left out from teaching as Matt Strassler did and it is vitally important.

Good to see a sensible question Paul.

Yep spot on.

Now do you want me to give you a logical problem that follows from this keep reducing the size of the box down to like microscopic.

Do you see what is going to happen?

At some point you will reach a size where you have one particle trapped in the box touching the walls.

Where does the field go now?

These are the problems of classic physics

gravity , that particle will have gravity.

then if you divide that particle a million times each of the million pieces will have gravity.

there will always be a field of some kind.

I'm thinking that even though they say its a classic physics problem the answers to
all of it can be found using classic physics , they're just not thinking the right way.

I'm also thinking that you guy's are getting trumped by your math.

I'm not trying to start an argument , just telling my opinion.

Lets see if I can stretch you .. this one usually catches the students out.

Whats the gravity at the centre of the earth?

Now what if I take your box to that centre of earth position?

since the rest of the earth's gravity ( due to mass ) would be pulling on the center of the earth , I'm going to say apx zero.

depending on where you measure within that particle.
of course I'm considering that the earth here is just
an example and we're not thinking of the actual earth.

because we really don't know what's there.



there may not be much gravity , but there's plenty of heat.
because there's plenty of pressure.

and loads of electric currents.
and electric currents produce magnetic fields !

to get pickey about it the rest of the universe is also
applying gravity to that particle.

Very good most get that wrong.

So lets keep the extension going the earths gravitaional field ends where?

And since you already introduced the earths magnetic field and it's source above lets extend that.

If we looked at the longest possible magnetic field line of the earth where does it start and end?

it never ends , it just get's weaker.



I'm going to say at the center of the earth.





don't get angry at this , this could be important stuff here.

if your math say's thing's are different than reality then could it be that the math need's fine tuning not reality?

I never get angry unless you are trolling .. I am also making no implicit claim I know the answer here because there are some big problems we are about to encounter and this excercise was about getting people to think.

Again you are absolutely correct science says the fields extend from the centre of earth to the very edge of the universe they just get weaker.

There is a huge problem in the above if we agree that fields are energy we have energy arising from a singularity at the centre of the earth and travelling off to an almost infinite edge of the universe .... houston we have a problem.

Classically and even in the explaination Matt Strassler gave we try to sweep this under the carpet. We try and make claims like the centre is only a notional idea its the point that the larger number of interactions centre on.

Sounds good until you drill down to the microscopic level where like in your earths magnetic field there is some charged particle moving that will emit a magnetic wave that will travel all the way to edge of the universe and at that level the energy arises at a singularity and ends in infinity.

We as smart humans struggle to get off the planet and yet some pathetic particle can send something to the edge of the universe ... about now I think it's probably time we discuss this energy stuff don't you?

yes

a gravity field is not energy.

a magnetic field is produced by energy and can produce energy but is not energy.

light is always energy.

that sound about right?

what do you think about a light field?

As per the discussion above I defined field as energy per volume it's my definition.

As per the standard science definition

http://en.wikipedia.org/wiki/Field_(physics)

=> A field is a physical quantity that has a value for each point in space and time

I have chosen to make the standard physical quantity energy I chose that because as per the logic given above it makes all field definitions uniform I am assuming there are no special fields.

So I am giving a series of assumptions and logic and see where it takes us, I am not claiming it to be true.

This was sort of my complaint with Matt Strasslers answers Bill.S posted because his answer on fields was sort of pathetic



So for me no a gravity field is energy.

I have reasonable grounds for the assumption pick up a bowling ball and drop it on your toe. Where did the energy come from it has something to do with gravity fields because take your toe and bowling ball into space and it doesn't happen.

However as science doesn't have a precise origin of gravity there is nothing wrong with your view and I am not claiming I am implicitly right but then you need to go back a step and tell me how you define a field because it's different to mine.



Again no a magnet and electric fields I am going to define as energy again I can see magnets and electric fields move things and do work so I think it's a resonable assumption but certainly not conclusive proof.



Yes I will agree on that one light being an EM field by my definition must be energy.


However from the above you can see our first big issue for science we must decide on a relationship between energy and fields and your answers illustrate that fact dramatically.

That still leads us inevitably to the next problem we need to define energy .. care to try one yourself?



Do you mean of the faraday type or something else this is a somewhat problematic term?

For the more advanced of you who wish to skip ahead and do some thinking

http://en.wikipedia.org/wiki/Aharonov_Bohm_effect

I see were going to need to define energy before we can define
what a field is.

to me gravity is a force not energy.
it can produce energy but only through interaction with other objects.

and

an magnetic field like gravity is not energy , it can produce energy
but only through interaction with other objects.

we need to define energy before we can continue.


I haven't had but 1 cup of coffee , so I'll be back.
my brain hasn't fully kicked in yet and it hurts to think right now.

lets hold off on that for now until we can agree on what energy
is.

Energy exists in many forms:

from wiki

Heat, a form of energy, is partly potential energy and partly kinetic energy.
In the context of physical sciences, several forms of energy have been defined. These include:

Thermal energy
x Chemical energy
x Electric energy
Radiant energy
x Nuclear energy
x Magnetic energy
x Elastic energy
x Sound energy
x Mechanical energy
x Mass (E=mc²)
Luminous energy


I have placed an x beside the types of energy that
should not be considered in space and underlined the type's
of energy that we should use in my opinion.

maybe we should just use an E and then label the type of energy

ie... E(radiant) or E(luminous) etc...

and if we decide to use another form we can.

I'm going to guess that radiant energy is the only one we
will need because luminous and thermal are both radiant energy.

what do you think?