What is magnetic field?

Did someone give you something over in the Y!A elections section?

This video will give you the answer: http://youtube.com/watch?v=fxC-AEC0ROk

When you watch, just remember that you the "inertial observer" will act like the aluminum block outside the field, and the charge will act like the block inside the field.

[The electron will happily go and make its little circles around the magnetic field line and the inertial observer will perceive a change in the magnetic flux based on his motion through the field.]

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Ok, I was flippant. But the video is an excellent example of Lenz's law, which in a slightly round about way applies here. (moving through a magnetic field induces a current which opposes the motion).

Your right (of course), it is actually an electromagnetic field, not a magnetic field. The inertial observer (and the electron) will perceive an electric field causing the acceleration. You can integrate all together with special relativity -- but I forgot how some time last century!

Um, no. The electron is undergoing acceleration, so the speed is not constant. At some point in time, the electron is moving slower than your frame of reference, at another time it has matched velocity, and further on it is moving faster.

Your assumptions about the velocity are correct for only one instant, a snapshot in time. And just because velocity is zero at time=t, doesn't mean velocity is zero at t-x or t+x.

Why is the magnetic force zero, just because you changed the frame of reference?

Edit:

What's the word?

Imaginary?