Three off The Plane

Rumpus in the hallway.  Vinnie dashes into my office, tablet in hand and trailing paper napkins.  “Sy! Sy! I figured it out!”

“Great!  What did you figure out?”

“You know they talk about light and radio being electromagnetic waves, but I got to wondering.  Radio antennas don’t got magnets so where does the magnetic part come in?”

“19th-Century physicists struggled with that question until Maxwell published his famous equations.  What’s your answer?”

“Well, you know me — I don’t do equations, I do pictures.  I saw a TV program about electricity.  Some Danish scientist named Hans Christian Anderson—”

“Ørsted.”

“Whoever.  Anyway, he found that magnetism happens when an electric current starts or stops.  That’s what gave me my idea.  We got electrons, right, but no magnetrons, right?”

“Mmm, your microwave oven has a vacuum tube called a magnetron in it.”

“C’mon, Sy, you know what I mean.  We got no whatchacallit, ‘fundamental particle’ of magnetism like we got with electrons and electricity.”

“I’ll give you that.  Physicists have searched hard for evidence of magnetic monopoles — no successes so far.  So why’s that important to you?”

3 electrons moving north“It told me that the magnetism stuff has to come from what electrons do.  And that’s when I came up with this drawing.”  <He shoves a paper napkin at me.>  “See, the three balls are electrons and they’re all negative-negative pushing against each other only I’m just paying attention to what the red one’s doing to the other two.  Got that?”

“Sure.  The arrow means the red electron is traveling upward?”

“Yeah.  Now what’s that moving gonna do to the other two?”

“Well, the red’s getting closer to the yellow.  That increases the repulsive force yellow feels so it’ll move upward to stay away.”

“Uh-huh.  And the force on blue gets less so that one’s free to move upward, too.  Now pretend that the red one starts moving downward.”

“Everything goes the other way, of course.  Where does the magnetism come in?”

3 electrons in B-field“Well, that was the puzzle.  Here’s a drawing I copied from some book.  The magnetic field is those B arrows and there’s three electrons moving  in the same flat space in different directions.  The red one’s moving along the field and stays that way.  The blue one’s moving slanty across the field and gets pushed upwards.  The green one’s going at right angles to B and gets bent way up.  I’m looking and looking — how come the field forces them to move up?”

“Good question.  To answer it those 19th Century physicists developed vector analysis—”

Electromagneticwave3D

Plane-polarized electromagnetic wave
Electric (E) field is red
Magnetic (B) field is blue
(Image by Loo Kang Wee and Fu-Kwun Hwang from Wikimedia Commons)

“Don’t give me equations, Sy, I do pictures.  Anyway, I figured it out, and I did it from a movie I got on my tablet here.  It’s a light wave, see, so it’s got both an electric field and a magnetic field and they’re all sync’ed up together.”

“I see that.”

“What the book’s picture skipped was, where does the B-field come from?  That’s what I figured out.  Actually, I started with where the the light wave came from.”

“Which is…?”

“Way back there into the page, some electron is going up and down, and that creates the electric field whose job is to make other electrons go up and down like in my first picture, right?”

“OK, and …?”

“Then I thought about some other electron coming in to meet the wave.  If it comes in crosswise, its path is gonna get bent upward by the E-field.  That’s what the blue and green electrons did.  So what I think is, the magnetic effect is really from the E-field acting on moving electrons.”

“Nice try, but it doesn’t explain a couple of things.  For instance, there’s the difference between the green and blue paths.  Why does the amount of deflection depend on the angle between the B direction and the incoming path?”

“Dunno.  What’s the other thing?”

“Experiment shows that the faster the electron moves, the greater the magnetic deflection.  Does your theory account for that?”

“Uhh … my idea says less deflection.”

“Sorry, another beautiful theory stumbles on ugly facts.”

~~ Rich Olcott

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