If we look into a reflection in space 0.5 light years away from Earth, we should see 1 year ago (given zero motion relative to earth, and 0.5+0.5=1 year.)
Where there is relative motion with photons at least isn't there a Redshift and the Doppler effect (edit: and a different parametric or chaotic convolution over large distances without e.g. helical polarization to shield the signal)
Magnetic fields reportedly have a maximum propagation speed that is also the speed of light c in a vacuum.
So, to recall Earth's magnetic field from 41,000 years ago with such a method would presumably require a reflection (41,000/2 = 20,500) light years away
Where there is relative motion with photons at least isn't there a Redshift and the Doppler effect (edit: and a different parametric or chaotic convolution over large distances without e.g. helical polarization to shield the signal)
Magnetic fields reportedly have a maximum propagation speed that is also the speed of light c in a vacuum.
So, to recall Earth's magnetic field from 41,000 years ago with such a method would presumably require a reflection (41,000/2 = 20,500) light years away