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Electromagnetic Spectrum Limits

-- Claire | March 29, 2022

Image showing an active M dwarf star, Proxima Centuari, in red with many star spots, ejecting a large stellar flare in yellow and white. Proxima Centauri b, a small Earth-like planet is seen in the distant right of the image.

Question:

What happens at the very extremes of the electromagnetic spectrum—are there defined limits to wavelength/frequency? Or, can radiation have infinitely small and infinitely large wavelengths? What is the longest radio wave that we are capable of detecting, and is there more radiation out there at even longer wavelengths that we’re missing?

-- Claire

Answer:

I believe that by definition the electromagnetic spectrum runs from 0 to infinite frequency or wavelength. There are practical limits, though, due to our ability to measure electromagnetic radiation. At long wavelengths, I believe that the longest wavelength measured is in the range 10^6 to 10^(11) meters. Sometimes called “geomagnetic pulsations”, these waves are thought to be generated by an interaction between the Earth’s magnetic field and the solar wind.

-- Jeff Mangum

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