This sounded completely false to me initially. When I think of taking mass and turning it into black holes, it involves squashing the mass into a strictly smaller volume.
Thus I would've expected the radius of the black hole to be necessarily smaller than the dimensions of the butter cube.
However, I now realize my mistake - in examples like squashing mount Everest or earth or a neutron star into a black hole, we're starting with masses that are stable/in equilibrium. This would not be the case for a cubic light year of butter!
Further, it looks like the radius is directly proportional to the mass. Given that mass grows cubic with respect to dimension, it's expected the radius of the black hole would eventually outgrow the cube of butter if made sufficiently large...
Thus I would've expected the radius of the black hole to be necessarily smaller than the dimensions of the butter cube.
However, I now realize my mistake - in examples like squashing mount Everest or earth or a neutron star into a black hole, we're starting with masses that are stable/in equilibrium. This would not be the case for a cubic light year of butter!
Further, it looks like the radius is directly proportional to the mass. Given that mass grows cubic with respect to dimension, it's expected the radius of the black hole would eventually outgrow the cube of butter if made sufficiently large...