There are certain laws of physics that heat must follow.

Take Kirchhoff’s law of thermal radiation, for example, which applies the idea of reciprocity to heat, and dictates that a surface’s ability to absorb heat at a specific angle and wavelength must also match its ability to emit heat at the same angle and wavelength.

It’s a rule that makes thermal energy difficult to control in ways we might like to, and although workarounds have been found before, they’re inefficient and volatile.