system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 why do things glow when they get hot?

Fundamentally, where does the light come from? Is it electrons being broken down into photons..?  If so, does that mean when something gets so hot it produces light that it technically loses Mass or how does that work??
gpt
The glow is called *black-body radiation*, and it happens at low temperatures, too. It's just that the light at everyday temperatures is a wavelength human eyes can't see. All objects emit black-body radiation, although the amount they emit ramps rapidly up with temperature (it scales with temperature [in Kelvin] to the fourth power).

The actual mechanism at the particle level is that temperature is the random movement of particles within a material. That random movement results in charged particles moving past one another and in electrons being bumped up and down between different energy levels, and both of those processes can convert some of the energy of particles in the material (in practice, generally electrons) into light. The electrons themselves aren't destroyed by this, but they lose (kinetic) energy. The emitting material does lose energy (and thus mass in some sense, since mass and energy are the same thing), but black-body radiation doesn't involve the destruction of particles, no.