Ask any question you want about Physics

originally posted by: MasterAtArms
a reply to: Arbitrageur

I'm feeling pretty stupid today, and my school physics was a long time ago. I don't mind being spoon fed but I'm either totally not thinking about this right or just down right forgotten everything

I meant to respond to MasterAtArms, not Arbitrageur. My mistake.

The magnetic and gravitational fields are like infinite energy. No matter how many objects are placed in them, they will exert the same force on each one. There is something there that is glossed over or ignored.

Trying for your own understanding of things is a noble effort. Something to remember is that science is taught to keep smart people in the system ( a bit suspect), and also to make them fit into a team (good practical reason).

Ok, I was squaring in the wrong place. It was 2.3333etc. Kg of mass.

a reply to: MasterAtArms

The magnetic and gravitational fields are like infinite energy. No matter how many objects are placed in them, they will exert the same force on each one. There is something there that is glossed over or ignored.

Trying for your own understanding of things is a noble effort. Something to remember is that science is taught to keep smart people in the system ( a bit suspect), and also to make them fit into a team (good practical reason).

Which actually gives me a new perspective on something I've always been interested in. Again, this is based on the very thin assumption that I have the equations correct, but if I do, the Little Boy device achieved approximately .0010938% of a perfect theoretical yield, based on a mass of 64kg of U-235. I seriously hope we never achieve perfection. That's somewhere around 700 or so milligrams of material. I knew that for all intents and purposes it was just a tiny bit above a fizzle, but wow.
And now, I'm able to look up a couple of other values to plug in and confirm that I have the equations correct, because either direction I calculate it from it does indeed come up to the the approximate 50.19 MT yield of the Tsar Bomba. Thanks for teaching me how to catch this particular variety of fish, my friends.

originally posted by: pfishy
Of course, I had to break a long-standing treaty with Mathematics and press the on button on my TI-30XIIS. And there's always the very strong possibility that I calculated it completely incorrectly.

I gave you an approximation of c so you wouldn't need a calculator, which is 3 x 10^8 m/s

Square that and you get 9 x 10^16 or 90 x 10^15 m^2/s^2 so if you multiply that by 3kg it's 270 x 10^15 Joules, which is already more than 210 x 10^15 Joules, before you even worry about the other 47 kg, right? So just 3 kg of mass theoretically contains more energy than the tsar bomb released but as pointed out already numerous times, that energy content can't readily be extracted. However it does confirm why the star trek creators liked anti-matter, which annihilates completely with matter so if you had 3kg of positrons and electrons you might actually get that much energy, but we can't do anything like that scale yet, since we only get miniscule bits of anti-matter here and there.

originally posted by: MasterAtArms
a reply to: Arbitrageur

I'm feeling pretty stupid today, and my school physics was a long time ago. I don't mind being spoon fed but I'm either totally not thinking about this right or just down right forgotten everything

OK here's a roller coaster example:

Conservation of energy

Lower left you're moving say 20 miles an hour. When you're moving this is called kinetic energy. KE on the bar chart showing your energy.
Let's say the height of the hill is such that you'll make it to the top but almost stall completely there, so your speed goes to zero.

KE is zero at the top of the hill, where all your kinetic energy has been converted to potential energy, so if you look at the bar graph, it shows the same bar height at the bottom of the hill and at the top of the hill, but it's been completely converted from kinetic to potential energy (PE) at the top of the hill.

Once you roll back down the hill on the right there's another bar graph showing about half kinetic and half potential energy, because you're still picking up speed going down the hill.

What if you started out at the lower left with zero speed? How would you get to the top? You've presumably been on a roller coaster before, right? The car latches on to a mechanism that uses some kind of motor to do work to lift you to the top. Once at the top, you're barely moving, but you pick up speed as you fall.

Now apply this to magnets. To pry the magnets apart you have to apply work, like hoisting the roller coaster car up the hill.
Once you have the magnets apart they have some potential energy, which can do work when you let them move toward each other, similar to the roller coaster falling down the hill and picking up speed. But, notice that you never get any more energy out, than you put in, so it's not a source of energy at all. It's just converting energy from one form to another. As you said, this is conservation of energy.

By the way the guy spending tens of thousands of dollars on this machine doesn't understand that, so if you don't understand it either at least you're not losing a small fortune like him from your lack of understanding:

www.rarenergia.com.br...


He thinks he can get energy from gravity pulling on things the way others think they can get energy from magnets pulling on things. Whether it's magnets or gravity, neither is an energy source.

But you may ask, what about hydroelectric power? We get energy from gravity as the water falls over the dam. We do, but what re-fills the dam? The sun does, when it evaporates water that falls as rain, so gravity isn't really the source of energy, the sun is. So you typically can't get more energy out of gravity or magnets than you put in (or that some other energy source like the sun puts in for you), though people like this guy never give up trying.

a reply to: Arbitrageur

If you had one magnet on a table with S facing up, and placed another magnet over it with its S facing down, in a setting such that it was impossible for the top magnet to fall to either side, so we would assume the top magnet would be "repulsed into place", what is going on between the magnets and in the magnets that without their physical bodies touching, their bodies can be held apart and kept apart? There must be some physical reason as to why this occurs, and thus the idea that there were invisible fields between materials was borne. Is the field between the magnets in that scenario pretty much a stationary medium, like a solid, or is there dynamic and flux?

a reply to: ImaFungi
Michael Faraday was trying to figure out this dynamic back in the 1830s, but he never felt he made a satisfactory explanation of why he didn't always get the results he expected when he rotated the magnets. Some elementary textbooks don't cover this, but one question you might ask is, if you rotate a magnet, does the magnetic field rotate with the magnet?

Experiments trying to answer this question led to the Faraday Paradox where some experiments led to apparent violations of Faraday's law of electromagnetic induction. Faraday didn't know about the electron and the discovery of the electron helped solve the puzzle.

Even more than a century and a half later in 1998, people published a paper about this phenomenon which you may find interesting:

Faraday's Final Riddle: Does the field rotate with a magnet?

The experiments were undertaken because there was distinct evidence in the literature that moving the magnet did not, in all circumstances, give the same result as moving the conductor. This is in direct contradiction of the Special Theory of Relativity, where relative motion should give the same result, whether it is the magnet or the conductor that is moved. The results of the new experiments, ironically, fit relativity theory, but disprove another basic theory of physics.
Faraday [1] showed in 1832 that a current was generated in a conductor when

: the pole of a magnet is moved laterally near a stationary conductor
: a conductor is moved laterally near the pole of a stationary magnet
: a conductor is rotated upon the North- South axis of a nearby stationary magnet

But, he also showed that when
: a magnet and conductor are rotated in unison upon the North-South axis of the magnet, a current is generated in the conductor
: a magnet is rotated about its North-South axis, no current is caused in a nearby stationary conductor. This result is astonishing, and is not mentioned in many textbooks; it could lead to embarrassing questions from students.

He concluded that "rotating the magnet causes no difference in the results; for a rotating and a stationary magnet produce the same effect upon the moving copper". In 1852 he said "No mere rotation of a bar magnet on its axis, produces any induction effect on circuits exterior to it" and, "The system of power in a magnet must not be considered as revolving with the magnet".

So does the magnetic field rotate with the magnet? This is why we rely on experimental results and not intuition. Some of these results don't seem intuitive at first, and solving this apparent paradox requires a deeper understanding than Faraday had.

a reply to: Arbitrageur

And heres the field of study for it.
en.m.wikipedia.org...

a reply to: Arbitrageur

Thank you.

Ok, so, Magnet laying on table with S facing up. Magnet hovering/repulsed over it with S facing down.

What is happening in the air/space between the magnets?

Are photons 'shooting'/'bouncing' back and forth a trillion of them per second? The same ones or when they get to each end they are destroyed and new ones are created?

Or is the space 'solid'ish; Are there not photons shooting back and forth, but just photons stacked on top of each other, vibrating back and forth in place?

Or; are the electrons in the top magnet, vibrating back and forth, and maybe actually spinning, maybe it has to do with their style of movement around their atoms, and the electrons make EM field waves, which is EM radiation right which are photons, and so because they are both S sides, we assume that means something about the electrons orientation and movement causes the result emanating from the S side to be different, perhaps simply said to be opposite, from N, and so because S is emanating in the same way as the S, the sameness of the way in which the electrons are moving, interacting with the space outside the magnet, meets the sameness of the other S, and this sameness reaction results in the magnets physically desiring to not meet.

originally posted by: Arbitrageur

originally posted by: pfishy
Of course, I had to break a long-standing treaty with Mathematics and press the on button on my TI-30XIIS. And there's always the very strong possibility that I calculated it completely incorrectly.

I gave you an approximation of c so you wouldn't need a calculator, which is 3 x 10^8 m/s

Square that and you get 9 x 10^16 or 90 x 10^15 m^2/s^2 so if you multiply that by 3kg it's 270 x 10^15 Joules, which is already more than 210 x 10^15 Joules, before you even worry about the other 47 kg, right? So just 3 kg of mass theoretically contains more energy than the tsar bomb released but as pointed out already numerous times, that energy content can't readily be extracted. However it does confirm why the star trek creators liked anti-matter, which annihilates completely with matter so if you had 3kg of positrons and electrons you might actually get that much energy, but we can't do anything like that scale yet, since we only get miniscule bits of anti-matter here and there.

originally posted by: MasterAtArms
a reply to: Arbitrageur

I'm feeling pretty stupid today, and my school physics was a long time ago. I don't mind being spoon fed but I'm either totally not thinking about this right or just down right forgotten everything

OK here's a roller coaster example:

Conservation of energy

Lower left you're moving say 20 miles an hour. When you're moving this is called kinetic energy. KE on the bar chart showing your energy.
Let's say the height of the hill is such that you'll make it to the top but almost stall completely there, so your speed goes to zero.

KE is zero at the top of the hill, where all your kinetic energy has been converted to potential energy, so if you look at the bar graph, it shows the same bar height at the bottom of the hill and at the top of the hill, but it's been completely converted from kinetic to potential energy (PE) at the top of the hill.

Once you roll back down the hill on the right there's another bar graph showing about half kinetic and half potential energy, because you're still picking up speed going down the hill.

What if you started out at the lower left with zero speed? How would you get to the top? You've presumably been on a roller coaster before, right? The car latches on to a mechanism that uses some kind of motor to do work to lift you to the top. Once at the top, you're barely moving, but you pick up speed as you fall.

Now apply this to magnets. To pry the magnets apart you have to apply work, like hoisting the roller coaster car up the hill.
Once you have the magnets apart they have some potential energy, which can do work when you let them move toward each other, similar to the roller coaster falling down the hill and picking up speed. But, notice that you never get any more energy out, than you put in, so it's not a source of energy at all. It's just converting energy from one form to another. As you said, this is conservation of energy.

By the way the guy spending tens of thousands of dollars on this machine doesn't understand that, so if you don't understand it either at least you're not losing a small fortune like him from your lack of understanding:

www.rarenergia.com.br...

He thinks he can get energy from gravity pulling on things the way others think they can get energy from magnets pulling on things. Whether it's magnets or gravity, neither is an energy source.

But you may ask, what about hydroelectric power? We get energy from gravity as the water falls over the dam. We do, but what re-fills the dam? The sun does, when it evaporates water that falls as rain, so gravity isn't really the source of energy, the sun is. So you typically can't get more energy out of gravity or magnets than you put in (or that some other energy source like the sun puts in for you), though people like this guy never give up trying.

I still find it fascinating how many technological advances Star Trek accurately, if inadvertently, predicted. Tablet computers, automatic sliding doors, and even the current theories on 'warp drive'. Roddenberry and his writers were visionaries.

originally posted by: ImaFungi
a reply to: Arbitrageur

Thank you.

Ok, so, Magnet laying on table with S facing up. Magnet hovering/repulsed over it with S facing down.

What is happening in the air/space between the magnets?

Are photons 'shooting'/'bouncing' back and forth a trillion of them per second? The same ones or when they get to each end they are destroyed and new ones are created?

Or is the space 'solid'ish; Are there not photons shooting back and forth, but just photons stacked on top of each other, vibrating back and forth in place?

Or; are the electrons in the top magnet, vibrating back and forth, and maybe actually spinning, maybe it has to do with their style of movement around their atoms, and the electrons make EM field waves, which is EM radiation right which are photons, and so because they are both S sides, we assume that means something about the electrons orientation and movement causes the result emanating from the S side to be different, perhaps simply said to be opposite, from N, and so because S is emanating in the same way as the S, the sameness of the way in which the electrons are moving, interacting with the space outside the magnet, meets the sameness of the other S, and this sameness reaction results in the magnets physically desiring to not meet.

Just a side note, but the photons could not be stacked on top of each other. Photons don't hold still like that. They can be trapped or slowed, but that is not the circumstance in which those occur.

a reply to: ImaFungi
The virtual photon model of the magnetic field makes predictions that are consistent with experiment, but if you can't see, smell, touch, taste or hear a virtual photon, I suspect you have your doubts about them. Even if you learn QED, at some point you're going to come up against the reason we call fundamental interactions "fundamental"...it means "we don't know".

van.physics.illinois.edu...

I can't resist giving the first two lines of a ~ 100 page interview that the Chemical Heritage Foundation conducted with a scientist (my father) who had been working with magnets for ~ 90 years. "As a kid I discovered that I could make the pins in a box stand up, and by moving a magnet around, I could make them march. I had no idea what a magnetic field was and I suspect I have no idea still what a magnetic field is, except for some of the things it does."

So, learn what the magnetic field does, and see if you can explain it any better than QED does using virtual photons which for now is the best model we've got. If you can explain it better, I'd be interested in seeing what you come up with, but by better I mean more consistent with experiment than QED and that's a tough challenge. For the hundredth or so time, you should probably start with reading the Feynman lectures.

a reply to: Arbitrageur

Am I missing something? I don't see the paradox.

Take magnetic dipoles aligned in some long axis, and the dipoles are embedded in rigid mechanical material. That's usually what we mean by a ferromagnet. You model this as some magnetization density pointing in the long axis, let's say it's a long thin cylinder with dipoles

Now if this mechanical material is rotated around its axis, the density of magnetization stays the same, just as the mass density stays the same.

Magnetization (density of elementary dipoles) is the source term for static magnetic fields, so if the magnetization is the same the external field stays the same. If external field is the same, then the flux through a coil is constant and so there is no induced emf or current.

I don't see this as being much different from asking what the static graviatation is outside a spherical planet of uniform density, does it have a time-dependence when the planet is rotating? No, not until very small GR effects.

a reply to: mbkennel

Before particle physics this was a problem. Now we have a working model and you no longer see the problem.But virtual particles explains the phenomenon of magnetism or at least matches observation. But it's very difficult for people to process. Electrostatic and magnetic fields involve the exchange of "virtual" photons . Very close to an electron is a dense cloud of virtual photons which are constantly being emitted and re-absorbed by the electron.This is why electrons are the key to magnetism. Some of these photons split into electron-positron pairs (or pairs of even heavier stuff), which recombine into photons which are re-absorbed by the original electron. These virtual particle loops screen the charge of the electron so that far away from an electron it appears as if it has less charge than close by.

Normally we wouldn't call any of these fields "matter", but it is true that the electric and magnetic fields which surround a charged object like an electron do store energy, and therefore have a rest mass as we know from E=mc^2. So I guess to answer a question we have matter repelling or attracting our particles through Columbs interactions.

But let me clarify something quickly magnetic fields not only have average values but also potential values. Meaning just like in an atom we can only determine the average position of an electron. In fields we can only determine the average of our field. But like particles these fields will attract or repel based on their average charge just like particles.

PS without understanding bosoms and spin and actually doing the math this is as close to an exploration as one can get. Laguage is not the right tool for this math has to take over for any further explination. And to go here you have to have the background.

originally posted by: mbkennel
Am I missing something? I don't see the paradox.

It's the opposite of missing something, you know too much.

You have to put yourself in Faraday's shoes to see why he had a problem with the experiment proving Faraday's law false when in many other situations it appears to be true.

Faraday paradox

in Faraday's model of electromagnetic induction, a magnetic field consisted of imaginary lines of magnetic flux, similar to the lines that appear when iron filings are sprinkled on paper and held near a magnet. The EMF is proposed to be proportional to the rate of cutting lines of flux. If the lines of flux are imagined to originate in the magnet, then they would be stationary in the frame of the magnet, and rotating the disc relative to the magnet, whether by rotating the magnet or the disc, should produce an EMF, but rotating both of them together should not.

So those are the results Faraday expected and why he expected them, but of course those aren't the results observed, thus why it was a paradox for him. You're making different assumptions than Faraday, which you may not even realize aren't obvious, so if you don't realize that, then that's what you're missing. Not only did Faraday never figure out an explanation he considered satisfactory, but the paper I cited lists some views for the next century that mostly got the answer wrong, because it wasn't as obvious to them as it is to you.

Of course it's not a paradox anymore, but it was to Faraday and even people who thought they explained the paradox after him had incorrect explanations.

originally posted by: pfishy


Just a side note, but the photons could not be stacked on top of each other. Photons don't hold still like that. They can be trapped or slowed, but that is not the circumstance in which those occur.

This is what you think, not what you know.

originally posted by: Arbitrageur
a reply to: ImaFungi
The virtual photon model of the magnetic field makes predictions that are consistent with experiment, but if you can't see, smell, touch, taste or hear a virtual photon, I suspect you have your doubts about them. Even if you learn QED, at some point you're going to come up against the reason we call fundamental interactions "fundamental"...it means "we don't know".

van.physics.illinois.edu...

I can't resist giving the first two lines of a ~ 100 page interview that the Chemical Heritage Foundation conducted with a scientist (my father) who had been working with magnets for ~ 90 years. "As a kid I discovered that I could make the pins in a box stand up, and by moving a magnet around, I could make them march. I had no idea what a magnetic field was and I suspect I have no idea still what a magnetic field is, except for some of the things it does."

So, learn what the magnetic field does, and see if you can explain it any better than QED does using virtual photons which for now is the best model we've got. If you can explain it better, I'd be interested in seeing what you come up with, but by better I mean more consistent with experiment than QED and that's a tough challenge. For the hundredth or so time, you should probably start with reading the Feynman lectures.

The past 30 posts in this thread of mine were attempting to get deeper into the nature of EM field. When asking how it is attached to electron, asking how much of it exists around electron at how many points, and when an electron is moved how the field moves, and how dense the field is throughout the universe, I have been asking tons of questions, that should get knowledgeable people to think about their ignorance.

Can you give me a starter description on virtual photons; as far as I know the theory is like; "dude I promise there is nothing there, just vacuum, and sometimes I say that vacuum is something, and sometimes when its convenient I say that vacuum is nothing, so this time I say that vacuum is nothing, and to avoid looking like idiots after so hardcorely denying aether theory to admitting that the universe is full of a dense medium of light field, we will pretend that this doesnt exist, until we detect a part of it, we will say that the aether is 'virtual', because how can we know something is there when we are not detecting it, uncertainty duh, so we dont assume that this virtual field has intrinsic mass at points, we dont know if it is in separate quanta or what it would even mean for it to be one fluid 3d sheet medium of energy essence, but it makes us feel good to pretend is doesnt exist and call it virtual, so before the S down magnet is placed over the S up magnet, there is an energy field being generated, by the electrons interacting so awesomely with nothingness, that a ton of photons just bounce up and down or shoot up and down, and then when we put the S down magnet on top, all the electrons are interacting with the aether, darn with the virtual photon field, which is nothing, the electrons in the S down magnet are interacting with the nothing, which forces a lot of real photons to come into existence, and the number of photons get real high between the magnets so the S magnet facing down cant possibly go to the ground because there are so many photons blocking its path, are there, is it photons that are blocking its path, or is it inherent massive and energetic field substance, and is not inherent massive and energetic field substance which may move what a photon is, minus our ruining decision and stubborn ever decision to set the photons mass at 0 therefore base everything else around this arbitrary decision'

Is the EM field anything but photons? If so, what is it? Energy lines? substance lines? With the magnet on table S facing up, before the other magnet is involved, arent the electrons in this magnet causing the space above the magnet to be novel, novel compared to space around other objects that are not magnets? If you put a detector above the magnet S facing up what sort of EM radiation would it be constantly detecting?

originally posted by: mbkennel
a reply to: Arbitrageur

Am I missing something? I don't see the paradox.

Take magnetic dipoles aligned in some long axis, and the dipoles are embedded in rigid mechanical material. That's usually what we mean by a ferromagnet. You model this as some magnetization density pointing in the long axis, let's say it's a long thin cylinder with dipoles

Now if this mechanical material is rotated around its axis, the density of magnetization stays the same, just as the mass density stays the same.

Magnetization (density of elementary dipoles) is the source term for static magnetic fields, so if the magnetization is the same the external field stays the same. If external field is the same, then the flux through a coil is constant and so there is no induced emf or current.

I don't see this as being much different from asking what the static graviatation is outside a spherical planet of uniform density, does it have a time-dependence when the planet is rotating? No, not until very small GR effects.

So is there a difference between; Well the control scenario is if I read you correctly to keep a magnet repulsed above another, to use a cylinder to hold them in place, though it would be preferable to imagine and do this without the cylinder, as that can only add to potential variables;

Magnet with S facing up, magnet with S facing down repulsed a distance of space above magnet with S facing up.

3 scenarios; 1. Grabbing the top magnet and turning it like a dial, and you are wondering how the field between them is altered and what effect this may have on a magnet or conductive wire placed parallel to the field and just outside the boundary of the magnets perimeter?

2. Grabbing the bottom magnet and lifting it up.

3. Grabbing the bottom magnet and moving it laterally to a side (and if there would be any difference on a magnet or wire depending on in relation to that wires position which out of 360 degrees of direction the bottom magnet was moved towards)

how long is a piece of string?

a reply to: Arbitrageur

Ah, so it's a paradox if one incorrectly considers the visual model of 'lines of flux" as being too close to the physical model, imagining that the "lines of flux" are physically attached like invisible mechanical objects to the ferromagnet, when they aren't. The lines are visual aids and representations of the vector field. And if the magnetic field is static in time in the frame of the detection coil, then there's no EMF.

My conception doesn't require particle physics though, just Maxwellian electromagnetism which can handle continuum dipole source terms.