system
Given the following post, respond as if you're commenting on Reddit:
human
If each atom has its own spectral lines, how does blackbody radiation cover all possible frecuencies?

I mean,a copper filament emits according to the temperature, but shouldn't it emit only in the "copper spectrum"?
gpt
The natural lines are broadened and shifted by different effects. There is Doppler broadening, which refers to the Doppler effect shifting the emission wavelength, because the emitter is moving. Since the particles have a random distribution of speeds, this converts a single spectral line into a Gaussian distribution. Similarly there are interaction effects (like pressure broadening), a particle temporarily shifts its energy levels (and thus its emission light), while close by another particle. These effects average out the narrow spectral lines and you end up with the black body spectrum.

But no object is a true black body radiator. E.g. if you put copper dust into a flame it will look more greenish than an ideal black body. Or look at fireworks, depending on their ingredient they glow in different colors.

TL/TD: It is a statistical effect, averaging out the emission from many particles being in random states.