How Can We Determine the Size of a Black Hole?

  • Context: Undergrad 
  • Thread starter Thread starter fillipeano
  • Start date Start date
  • Tags Tags
    Black hole Hole
Click For Summary

Discussion Overview

The discussion revolves around methods for determining the size of a black hole, focusing on theoretical calculations and conceptual understandings of black hole dimensions, particularly the event horizon and singularity. The scope includes theoretical aspects and conceptual clarification regarding black hole properties.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant inquires about determining the size of a black hole, expressing difficulty in finding answers online.
  • Another participant suggests that the diameter can be theoretically derived from the mass of the black hole, providing examples of mass-to-diameter conversions.
  • A different participant notes that black hole size is typically expressed as the size of its event horizon, which can be calculated relatively easily.
  • Some participants emphasize that the event horizon is an effect of the black hole, stating that the singularity itself is thought to have zero volume.
  • There is a mention of the existence of various theories regarding black hole interiors, which may lead to different interpretations of size and structure.

Areas of Agreement / Disagreement

Participants express differing views on the nature of black hole size, particularly regarding the event horizon and singularity. There is no consensus on the implications of various theories about black hole interiors.

Contextual Notes

The discussion highlights limitations in current understanding, including the dependence on theoretical models and the lack of empirical measurements of black hole diameters.

fillipeano
Messages
51
Reaction score
0
Is there any way to determine how big a black hole is? I googled the question but I didn't find any answer.
 
Astronomy news on Phys.org
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.
 
Last edited:

Similar threads

High School How Can Black Holes Vary in Size if They Are Singularities?
  • · Replies 20 ·
Replies
20
Views
3K
High School Gravitational effects of a small black hole passing your body
  • · Replies 1 ·
Replies
1
Views
863
High School Confusion regarding black hole spin
  • · Replies 40 ·
2
Replies
40
Views
4K
High School I Need Help on Understanding Some Basic Astrophysics / Sand Clock Universe
  • · Replies 5 ·
Replies
5
Views
3K
Undergrad Does light bend around black holes?
  • · Replies 49 ·
2
Replies
49
Views
6K
Undergrad Can there be slowly-falling accretion disks in black holes?
  • · Replies 11 ·
Replies
11
Views
2K
Undergrad Light curving around vortex simulating a black hole
  • · Replies 5 ·
Replies
5
Views
3K
Undergrad Amount of black hole entropy inside the Universe?
  • · Replies 5 ·
Replies
5
Views
3K
Undergrad The initial density of an object and its compression into a black hole
  • · Replies 17 ·
Replies
17
Views
5K
Undergrad Early Universe massive Black Holes question
  • · Replies 10 ·
Replies
10
Views
3K