system
Given the following post, respond as if you're commenting on Reddit:
human
What is the speed of magnetism?

Something I was pondering yesterday, and couldn't get a straight answer by googling the question, so I thought to come here.  Basically, here is the problem, and i'm curious of an answer.

Say you have a laser beam, attached to a switch, which is attached to a power source.  A mile away from the laser, you have a photoresistor, attached to a computer to record the time of the wave arriving at the resistor. 

Next to this laser, you have an electromagnet, which is attached to the same switch and power source.  Yet again, a mile away from the electromagnet is some receiver that detects magnetism, and is attached to the same computer to record data side by side.

My question: When the switch is pressed, will the magnetic field arrive ahead of light?  Do not include resistance of the wire, or time it takes for either to create a magnetic field, or a beam of light.  Purely speed.  Does magnetism have a speed?
gpt
It sure does.  And you may (or may not!) be surprised to know it travels as the same speed as light, c.  The main reason is that the force carrier for the electric field is the same force carrier for the magnetic field (the photon).

Electricity and magnetism were found to be manifestations of the same fundamental force way back in the late 1800's by Maxwell.