system
Given the following post, respond as if you're commenting on Reddit:
human
If some of the mass within a system was converted to energy, would there be a drop in the gravity detected from that system?

If not, how does energy relate to gravity the way we are taught mass does?
gpt
Only if it radiates away. Gravity depends on the entire energy density of the system (technically, the stress-energy tensor), and the mass is the energy in the rest frame of that object. For example, if you had some kind  of reflective spherical cavity with an extreme density of gamma radiation inside, such that there was an equilibrium between positron-electron production and annihilation, the external gravitational monopole field would be unchanged depending on how much electrons or photons were in it at a given time. If light can escape though, the system would lose mass as it radiates energy away.