# Einstein & Relativity theory fading

#21

I’ve not thought a lot about it but I’d imagine some ratio of weight to thrust equation would be involved. also: perhaps any weight spinning at such incomprehensible speeds would not have to be counterbalanced? maybe it goes so fast vibration doesn’t even have time to happen? FTL? It’s neat to think about and it quickly gets deep in technicalities but we know there is stuff that moves FTL some of which will be needed the further we venture from earth for communications etc. I just think it unproductive to believe in barriers, we can not even start the research for FTL without first believing it is possible. (FTL) faster than light.
PS; KP, I would have to think hard to keep up with you, sorry, but it’s beyond me right now!!

#22

Oops my bad . I used the example of a donut shape as a general case to show the fields could be arranged perpendicular at some point. But to answer above my old standby ref may make it easier.

v

No sine waves involved. For two parallel conductors what happens depends on direction of current flow. See fig c and d below.

#23

Thank you, Chief.

But in the case of AC, the field isn’t sinusoidal? And isn’t the electric field at a right angle to the magnetic field? They always show it like this, supposing the fields to be flat. But they aren’t really flat, are they? I think they look like rotini, maybe.

#24

emrobu; you’re probably talking to KP so this is for you both: i believe the theory of levitation would only require a rotating field (mechanical) to be in but one plane, when this plane is moved then the craft would move with it… just a theory… maybe? maybe tomorrow i’ll look at what you’re doing with the conversation!!

#25

@jimrr
If you want to see a rather big gyroscope, look outside now, it is just full moon:
The moon turning around the spinning earth forms a gyroscope

The moon’s orbit around the earth-moon barycenter (1400 – 2000 km below the earth’s surface) takes about 27.3 days mean. This is enough to stabilize the earth’s spinning axis at about 23.4° relative to the earth’s orbit around the sun (the ecliptic).

Without the moon, perturbations from other planets would slowly turn the earth axis in the sun’s direction, then away from the sun etc. I do not know how fast this movement could be, but days and nights of say 50000 years each would not have permitted life on earth.

A useful gyroscope!

#26

Emrobu - yes that was for DC of course. Actually I don’t understand what that graphic is getting at. Magnetic field vs electric field? But no I don’t believe the field would have a shape like that.

Let’s just consider a single conductor of a single phase AC circuit. The current builds up in one direction, peaks, decreases, reverses, etc the current conforming to a sine wave yes. But the magnetic field would build up, decay, reverse but still be formed according to the left hand rule. So the field should still be a cylindrical “shape” that grows with flux lines in a CW direction, then collapse and form again with lines in CCW.

#27

That diagram is showing several wavelengths of a generalized electromagnetic wave with its magnetic and electric components traveling through space (or some other medium).

At sixty hertz, one wavelength would be five thousand kilometers long, so for any reasonable length of wire you’d be looking at what would appear to be a constant level from one end of the wire to the other, increasing and decreasing together.

#28

Ok. Thanks for straitening me out. Bear with me while I make sure. I was really starting to feel like EM had to be 4 dimensional, which doesn’t seem to be the case. Are you happier with this model, where blue is magnetic field and red is electric field? In this case, I think wire would pass vertically through both annuluses.
Then, as KPChief says, it builds up, collapses, reverses, builds up again for AC, and as dbeierl says, the wavelengths are too long to worry about.

Why didn’t someone just say: Em, its a jam donut. Time for a celebratory breakfast at Timmy’s. I hope there’s a chocolate magnetic field and a raspberry electric field.

#29

I’m not used to seeing the electrical field illustrated. Usually illustrations just show the magnetic field around a wire. That’s what’s been confusing me.

#30

I think there may be more than one conversation going on here. I was taking the issue as related to the interactions of electrical currents, associated magnetic fields and mechanical forces within electrical apparatus (engineering) as opposed to the phenomena of the electromagnetic force (physics).

I would not be the best source for the physics side of things. But simplistically, electric fields surround (stationary?) charged particles whereas magnetic fields arise from the motion of charged particles (current) or a magnet. Together they are considered the fundamental electromagnetic force.

With respect to your graphic then, if a wire were running through the annulus vertically and it were carrying an electric current, that would produce a magnetic field with lines of force / flux orientated as the red lines are and extending off into space. If a stationary charged particle were at the center of that sketch it would be surrounding by an electric field that I’m not sure could be represented by lines at all but more by a uniform spherical cloud(?).

Does a charged particle’s electric field move along with it as a current travels along creating a (essentially) cylindrical magnetic field? Could that even be separated out at that point? Is it like potential energy being converted to kinetic energy?

Not sure that helps you at all. If I come across something more will post it but I guess my experience is at the engineering level not the physics level.

#31

nothing is surprising anymore, just these days I learned that there are plans for a lift from earth into space to be built by 2050.

#33

yabbut, they haven’t invented the ‘wire’ yet. nothing we have yet will hold even its’ own weight at the necessary distance.

#34

it’s probably a projection… and they seem to be rather accurate at it too. gawd, i’ll have to make it into my 90’s to see it, just think of all the krap they can haul up there, REALLY BIG space stations and stuff.

#35

Maybe @dbeierl can correct me if I’m wrong but I believe the the x-y-z coordinates are just rotated so the math works.

A 2 dimensional example would be say, a sine wave that’s been rotated 90 degrees.
Like this one

The math for the sine curve might be tough but if you rotate the x-y axis 90 degrees clockwise it’s just a standard sine curve, the math is going to be less convoluted.

Now with the two components of the electromagnetic fields at right angles to each other. In your 3 dimensional diagram with the two fields (red and blue) the math for the red Electric field is going to be easy, it’s a sine curve. If there is another 2 dimensional field at right angles it can be flipped up so it’s a standard sin curve.

It’s like flipping over a piece of equipment 90 degrees in the shop vice so the other side can be worked on.

#36

I think that the sine wave appearance is a simplification or a projection. It really should look more like a rotini.

Or you can think of the sines as being shadows, maybe:

What’s interesting about this drawing is that the two shadows that are shown sine waves at 90 degrees to one another. Its tempting, then, to wave my arms around and say: see? electric fields and magnetic fields are just two shadows of the same great rotini!!11!! But I don’t think that’s actually true.

Laithwaite made these demo videos. If you go forward to 12.5 min in this clip, he puts iron filings on his linear induction motor and we can really see what the shape of the magnetic field is. These don’t look like rotini, neither do they look like donuts. He says he running AC through that apparatus.

Also, considering what has been said in this thread so far and what Dr. Laithwaite’s book is telling me, I’m becoming aware of how deep my confusion is on the subject. This poor abused topic is supposed to be about relativity. Laithwaite did see a fundamental connection between Einstein’s work and magnetism, but I’m not yet able to understand it.

#37

Well, I’m not sure but I think that’s right, it’s two shadows of the same great rotini.

That video was interesting but I don’t think it helps, there are waves everywhere. I see fir waves.

But I wasn’t a very good student so…

#38

@Kennebec_Captain sorry, I’m working at the edges of my understanding here.

@Emrobu I’m curious why you think it’s a rotini. Is it because the trigonometry works conveniently by thinking of a cycle as a complete rotation?

Again, remember that you’re working with power frequencies where the wavelength is five million meters long (to see one complete cycle stretched along your wire). Any change in field at any point on your wire propagates along the wire at about 95% of 300 million meters per second.

#39

I guess I got the notion from reading about polarized light. For example.

I’m really grateful for you pointing this out. You thinks to yourself, oh radio waves are really little… and you forget that its because they are measured in Megahertz, and that’s a really big difference from Hertz, and it totally matters. Thanks for reminding me. I accept that the wavelength doesn’t mater at all in a 60 hz system.

So the magnetic field is, as KPChief says, like this:

Where the rings are really cross-sections of shells around the wire which dive in at the north and south ends.

And the electric field looks like sun-rays around the wire:

So, its easy to see that the magnetic circles and the electric rays are perpendicular, no extra dimensions needed. And then you look at the rays around the red wire, and you wonder: why like that? is that a rotini? >.>

#40

The Navy used to have a transmitter that ran down around twenty hertz, IIRC. They used it to talk to submerged submarines. But the antenna took up a substantial chunk of the state of Michigan (?), and it took half an hour to transmit a three character message.

#41

Yes, ELF Radio. My instructor when I took my AB licensing class at NPFVOA was a submarine navigator for the Navy in a former life. He told us about this.

There was some talk that ELF and ULF could be used to predict earthquakes. The idea is that the rocks strain before they break, and the strain has a piezoelectric effect that broadcasts in the ELF or-and ULF bands prior to an earthquake.