How can black holes have electrical charge, and spin?

In summary: The term "singularity" refers to a point of infinite density, not zero volume. In summary, the laws of conservation still apply during the creation of a black hole, so if a star has angular momentum/charge before collapsing, the resulting black hole will also have it. Additionally, the claim that black holes have zero volume is incorrect as the term "singularity" refers to a point of infinite density, not zero volume.
  • #1
Lamdbaenergy
35
1
If the star's mass supposedly collapses into a single point, and it ends up having "said" zero volume, then how can people say that the hole has a specific spin or that it can have an angular momentum?

Does it mean that the singularity is somehow still spinning, or maybe the spacetime around it is just being dragged for some reason?
This subject has been confusing me quite a bit whenever I think about it.
 
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  • #2
Where would the charge and angular momentum of the star go otherwise?

On a related issue: Elementary particles are also modeled as point like, yet can carry both intrinsic charge and angular momentum.
 
  • #3
Lamdbaenergy said:
If the star's mass supposedly collapses into a single point, and it ends up having "said" zero volume, then how can people say that the hole has a specific spin or that it can have an angular momentum?

Does it mean that the singularity is somehow still spinning, or maybe the spacetime around it is just being dragged for some reason?
This subject has been confusing me quite a bit whenever I think about it.

Sometimes the BH's gravity field is referred to as a 'fossil' field-

http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/black_gravity.html
 
  • #4
Turns out Kerr and Newman black holes do NOT contract into points. They contract to circles... which still have zero volume, because zero thickness throughout their nonzero circumference.
Reissner black holes are point charges, just like Schwarzschild black holes.
 
  • #6
In short: the laws of conservation (angular momentum, charge, mass-energy, etc.) still work during the process of creation of a black hole. So if a star had some angular momentum/charge before it collapsed, the resulting black hole will also have some (assuming the angular momentum/charge was not radiated away during the collapse).

Also, the claim that black holes have "zero" volume is simply incorrect.
 

Related to How can black holes have electrical charge, and spin?

1. How can black holes have electrical charge?

Black holes can have electrical charge because they are made up of matter, which can have positive or negative electric charges. When matter falls into a black hole, it can bring electric charge with it, causing the black hole to have a net electrical charge.

2. How do black holes spin?

Black holes can spin because they are formed from the collapse of a massive, rotating star. Just like how a spinning ice skater can increase their speed by pulling in their arms, the rotation of the collapsing star is amplified as it shrinks into a black hole, causing the black hole to spin.

3. Can black holes have both charge and spin?

Yes, black holes can have both electrical charge and spin. In fact, most black holes in the universe are believed to have both properties, since they are formed from rotating stars and are constantly attracting matter with electric charge.

4. How do charge and spin affect black holes?

Charge and spin can affect black holes in various ways. Electric charge can affect the way black holes interact with their surroundings and can even contribute to the formation of jets of particles that shoot out from the black hole's poles. Spin can also affect the behavior of black holes, such as increasing the rate at which they consume matter and altering the shape of their event horizon.

5. Can the charge and spin of a black hole change?

Yes, the charge and spin of a black hole can change over time. As black holes continue to attract matter, their charge and spin can increase or decrease depending on the properties of the matter being absorbed. Additionally, black holes can merge with other black holes, which can also cause changes in their charge and spin.

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