How can we observe lights properties if it travels at the speed of light, or can we?

Question

Special relativity says that anything moving (almost) at the speed of light will look like its internal clock has (almost) stopped from the perspective of a stationary observer. How do we see light as alternating electric and magnetic fields? Also does light never age?

Answer 1

The time stands still for light indeed, so it will never age.

You can think of the photon as a sine wave shaped electric field fragment traveling at $c$, and you can measure it's amplitude and frequency as it flys past your instrument. The photon itself does not oscillate.

(Bit oversimplified but probably you get the point.)