Researchers at the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) have developed an innovative method to study ultrafast magnetism in materials. They have shown the generation and application of magnetic field steps, in which a magnetic field is turned on in a matter of picoseconds.
Such a magnetic field (change) will propagate (at the speed of light in vacuum) during that time (10-12 s) to a distance of about 0.3 millimeter. So, don’t go too far away if you want to see that change happened this fast !
Blink and you’ll miss it. xD