How Can We Determine the Size of a Black Hole?

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The size of a black hole is theoretically determined from its mass, with the event horizon being a key measurement. For example, one solar mass corresponds to a diameter of approximately 5.9 kilometers. Actual measurements of black hole diameters are currently lacking, but future observations, particularly of the Milky Way's central black hole, may provide data within the next decade. It's important to note that the event horizon is an effect of the black hole, while the singularity itself has no physical size. Various theories exist regarding black hole interiors, leading to different interpretations of their characteristics.
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Is there any way to determine how big a black hole is? I googled the question but I didn't find any answer.
 
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If you mean its diameter, you can determine it theoretically from its mass:
1 solar mass = 5.9 km,
1000 solar masses = 5900 km and so on.
AFAIK, there are no actual measurements of a diameter. Maybe within the next 10 years, they will have measurements of the BH in the center of the Milky Way.
 
Black hole size is usually expressed as the size of its event horizon, which is pretty easy to calculate.
 
yes, but it should be noted that the EH is an effect caused by the BH. the actual BH itself has no size, ie, the singularity proper has zero volume.
 
jnorman said:
yes, but it should be noted that the EH is an effect caused by the BH. the actual BH itself has no size, ie, the singularity proper has zero volume.

That's only if a certain picture of black hole interiors is correct. Several different theories are available with quite different outcomes. Thus the event horizon is the boundary as far as we know or close to.
 
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