What are magnetic field lines made of?

originally posted by: Dr X
a reply to: DeadCat

When you spread iron filings near a magnet, there are distinct lines that they surround and align with. If it was simply a field then the filings would spread uniformly. Physics textbooks conveniently ignore this fact.

originally posted by: mbkennel
This isn't true. The "lines" are human-friendly visual representation of a vector field, the same way that contour lines on an topographic elevation map are a human-friendly representation of an altitude scalar value on an otherwise 2-d map.

There are no lines in the physics, just vector fields.

You're right that there vector fields instead of lines in the physics, but the iron filings do form distinct lines and you didn't really explain why. It's because if there aren't many filings, they form N-S magnets themselves and then they tend to form a "chain" of NS magnets attracting each other, and these chains of NS magnets are what form the lines.

If you keep adding more and more filings they will have more of a tendency to fill the gaps that were present when the filings were sparse, so the filings then make more lines because there are more of them to form "magnet chains", but obviously the field hasn't changed, so this should demonstrate the filing lines have more to do with the filings themselves and their alignment, than the field they are subjected to.

a reply to: Dr X

Hello again Dr X,

Thank you again for your response.

Yes, I know about the experiment that confirmed gravity waves. I find it very interesting that science has discovered another of Einstein's predictions to be true. The fact that gravity is expressed as a wave, (or a field?) is quite interesting. This also why I started thinking along the lines of waves and fields and how we can reflect or deflect them. I am very intrigued by the thought that we could use magnetism in a way that could deflect or reflect other types of waves or fields. Similar to the way the earth's magnetic field does. When considering the earth's magnetic field, many types of waves/particles are deflected away from us. As far as I have learned, it is because of the magnetic field that surrounds the earth. I find there are many amazing properties related to magnetism that most individuals don't really think about.

I truly appreciate your response, and thanks again.