Magnetic attraction

[mistermack]

I sort of understand how gravity can exert a force on matter.
The curvature of space-time does tie in well with it.

But how do magnets attract each other without touching?
Does a magnet cause space-time to curve? No. Otherwise, everything would be attracted to a magnet.

Just saying "magnetic field" doesn't explain anything. It DESCRIBES what happens, it doesn't EXPLAIN it.

Anybody got an explanation?

[dj357]

[Xamonas Chegwé]

One explanation is that electromagnetism (and the strong and weak forces) do warp spacetime. However, unlike gravity, the extent of an electromagnetic field is far more limited and so we don't experience this warping in our macroscopic view, only its effects - such as magnetic attraction.

However, shoehorning a "common sense", intuitive description onto quantum effects is always a tricky thing to attempt. Quantum particles/waves simply don't behave anything like the large objects (those that we can directly experience) appear to. Larger objects only behave as they do due to enormous numbers of quantum probabilities summing to predictable behaviour - at the Planck level, only probabilistic possibilities exist - and electromagnetism pretty much takes place on that scale.

To truly understand magnetic attraction (or any other effect of the electromagnetic field) you need to understand the mathematics of quantum mechanics. There really is no intuitive explanation that is as simple to follow as relativistic space-warping. Relativity, dealing as it does with the motion of the very large and fast, is fundamentally incompatible with quantum physics as we now understand it. Reconcile the two and look forward to your Nobel prize.

If you really want to try and understand such things in depth, I can recommend the free, Youtube lectures from Stamford university (delivered by Leonard Susskind - one of the founders of string theory) which, while frying your brain, will introduce you to the language that scientists trying to get to grips with such things MUST speak! For a simpler overview, there are plenty of pop-sci books out there: Brian Greene's Elegant universe, Brian Cox's The Quantum Universe are both worth reading.

If you do choose to try and master the maths - be warned that it is HARD! You will need a working knowledge of differential equations, partial derivatives, complex algebra, multi-dimensional topology, group theory, and a lot more besides - before you start!

I am plodding through it and I have a maths education equivalent to 2nd year degree level - trust me, the maths in general relativity is much much easier! Good luck!

[mistermack]

Thanks Xamonas.
Unfortunately, I hate maths. I abandoned it years ago. Even though I wasn't doing any worse than many others, I hated it more. Besides, describing something mathematically, and understanding it, are two different things. I'm no Einstein, but even he had a whizz mathematician to process the worst of it. (so I've read somewhere).
Newton described gravity mathematically, but had no idea what caused it.
Einstein with the curvature of space, has got a lot closer to understanding it.
That's what I was wondering, if there is something similar for magnetism.

They must be closely linked, as the speed of gravitational effects is identical to the speed of electromagnetic radiation. It can't be coincidence.

If spacetime being warped was the explanation, then a magnet would attract ANY matter. Maybe there are different components of spactime being affected.

It just annoys me that I can hold two magnets 1 cm apart, and feel the pull, and nobody can say why.
They can say HOW in enormous detail, and accurately predict what, when and how much, but not why.

[Gawdzilla Sama]

Lines of force bond when they cross. Simple enough.

[laklak]

The lines cross. Goddidit.

[mistermack]

Lines of force bond when they cross. Simple enough.

Unfortunately there's no evidence of lines. We draw lines to represent a field, but there's no evidence that actual lines exist.
Anyway, a line has an infinitely small thickness, of zero, so it's not likely that it could exert any force, or bond.

[rachelbean]

thank you.

[Jason]

Lines of force bond when they cross. Simple enough.

Unfortunately there's no evidence of lines. We draw lines to represent a field, but there's no evidence that actual lines exist.
Anyway, a line has an infinitely small thickness, of zero, so it's not likely that it could exert any force, or bond.

Sure there is. For an empirical test, scatter a small amount of iron filings on a piece of paper then place your magnet underneath it. Watch as the filings align themselves along the force lines from pole to pole.

[Xamonas Chegwé]

They must be closely linked, as the speed of gravitational effects is identical to the speed of electromagnetic radiation. It can't be coincidence.

The electromagnetic force is much greater than the force of gravity - by 36 orders of magnitude - ie. it is 1,000,000,000,000,000,000,000,000,000,000,000,000 times stronger!

Both are infinite in extent and decrease in strength inversely proportional to the square of distance.

BUT

Gravity is ALWAYS attractive whereas electromagnetism can be either attractive or repulsive. So, where mass (via gravity) always warps spacetime in the same direction and the cumulative effect of a huge amount of matter can result in the observable effects that Newton's equations and Einstein's relativity show, electromagnetism warps spacetime in opposite directions, dependant on the charge of the particle. So the electromagnetic force tends to cancel itself out over macroscopic distances - as the number of positively and negatively charged particles in the universe are (assumed to be and probably are) equal. It is only where there is a local imbalance that effects such as magnetic attraction become evident.

[Gawdzilla Sama]

Lines of force bond when they cross. Simple enough.

Unfortunately there's no evidence of lines. We draw lines to represent a field, but there's no evidence that actual lines exist.
Anyway, a line has an infinitely small thickness, of zero, so it's not likely that it could exert any force, or bond.

There are no latitude or longitude lines, but I can get there from here.

[Xamonas Chegwé]

Lines of force bond when they cross. Simple enough.

Unfortunately there's no evidence of lines. We draw lines to represent a field, but there's no evidence that actual lines exist.
Anyway, a line has an infinitely small thickness, of zero, so it's not likely that it could exert any force, or bond.

There are no latitude or longitude lines, but I can get there from here.

That's a pretty good analogy, as it happens. The lines don't actually exist but if you pretend they do, and do the maths, it produces verifiable results - like your plane landing where it's supposed to!

The same is true of the maths in QED and General Relativity - they are not "truth", merely models that mirror reality closely enough for our uses. We simply can't observe what is really going on at those levels - all we can do is observe how they affect things at 'our' level and extrapolate that into better and better mathematical representations.

[Gawdzilla Sama]

That's the analogy I got from a physics prof at Purdue. He was drunk at the time, but nobody had ever seen him sober...

[Xamonas Chegwé]

That's the analogy I got from a physics prof at Purdue. He was drunk at the time, but nobody had ever seen him sober...

A wise man indeed!

[mistermack]

The electromagnetic force is much greater than the force of gravity - by 36 orders of magnitude - ie. it is 1,000,000,000,000,000,000,000,000,000,000,000,000 times stronger!

Both are infinite in extent and decrease in strength inversely proportional to the square of distance.

I'm not arguing, but, for the sake of discussion, can they actually be infinite in extent?
Just going on the often repeated mantra that there are no actual infinites.

From a quantum point of view, I can see a situation where a gravitational effect drops to such a low level, that it can't achieve the minimum quantum effect needed to progress any further.
Same with electromagnetic force. Pure guesswork on my part, but it would reconcile the impossibility of an actual infinity.