# How large or small can frequency in the EM spectrum get?

The largest frequency range is gamma rays, but does the EM spectrum 'stop' somewhere? Like is there a limit to how large a frequency can get? Or how small frequency can get? Is it one of those things that theoretically nothing is stopping it, but nothing in the universe can produce ways of such a frequency or beyond a certain limit?

Does light from galaxies redshift to the point where the wavelength is just insanely long? Long enough that we can't see them?

• duplicate: physics.stackexchange.com/q/43063 – Paul Aug 18 '15 at 14:46
• Maybe the longest EM wavelength is equal to the universe's causality horizon? How could the universe produce a wave that can't fit inside the causality horizon? – Cham Sep 19 '19 at 1:59

I'll start with the second of your questions. Yes, light from very distant galaxies gets redshifted to such long wavelengths that there practically isn't any light to see. The lower limit on frequency is zero. Obviously. Technically one could say there is no signal at $0\,Hz$, but that still put a lower boundary on the frequency. Objects on the edge of our cosmological horizon have their light redshifted almost infinitely by the time it reaches us.