White electromagnetic radiation

[Jeff Root]

A Planck or blackbody distribution of photon energies has a curve
which is essentially zero at high energy, quickly rises to a peak,
and then slowly drops off at lower energies.

Would it be possible -- at least "theoretically" -- to have a
distribution in which the curve rises to a peak and then stays at
about that level all the way down to zero photon energy?
What sort of properties would this radiation have?

-- Jeff, in Minneapolis

[Ken G]

It can't be constant all the way down to zero frequency, for two reasons.
1) it would require an infinite number of quanta at low frequency, which can't occur from a physical mechanism in finite time, and
2) you really can't make photons at frequency f unless you have a time of order 1/f available. As the universe is only 14 billion years old, that's a limit on how low the frequency can go. Still, if you just mean can the spectrum go down to low frequencies as far as you'd care to measure it, I don't see why not.

[neilzero]

Can we measure/detect photons/ RF in the pico hertz range or even the millihertz range? Neil

[korjik]

Can we measure/detect photons/ RF in the pico hertz range or even the millihertz range? Neil

Milihertz is used in some magnetosphere research. Much slower than that would be treated as a long term fluctuation in a DC field. One picohertz is a 31000 year period.

[jlhredshift]

Milihertz is used in some magnetosphere research. Much slower than that would be treated as a long term fluctuation in a DC field. One picohertz is a 31000 year period.

See Ground Wave for the lowest "useable" frequency that I know of.