<p>???</p>
<p>ps: if you claim you do you have to explain how a magnetic field in one reference frame is a electric field in another (how the fields are two aspects of the same thing)</p>
<p>also, why doesn’t gravity have the same duality (does it have to do with there being both “positive” and “negative” charges in electromagnetism whereas there’s only one type of mass in gravity?</p>
<p>If you don’t understand it, then just post {or not post} whatever you like (hopefully its related).</p>
<p>Magnetism is a purely relativistic effect. If you look at the field of a charged particle moving near the speed of light, the field lines flatten due to the Lorentz contraction. The resulting field is symmetrical to a plane perpendicular to the motion of the charge.
To find the field in another frame, you can use the Lorentz transform of the fields. The magnetic field was defined before special relativity as something completely different, it can still be used as a tool, but the transform is where it comes from. The E and B field form the electromagnetic field tensor, the observed E and B fields depend on your frame of reference.
Now you may ask, why can we observe magnetism in everyday life if it is a purely relativistic phenomenon? Its because in materials like iron, all of the small fields align and add by superposition.
One last note, maxwell’s equations provide the fundamental and accurate description of electromagnetism. They are more fundamental that newton’s laws because they are based on symmetries of space. This is where einstein started in his theory of special relativity.</p>