Question about black holes and gravity

Click For Summary
SUMMARY

The discussion centers on the properties of black holes, specifically their mass, charge, and angular momentum, as defined by the "no hair theorem." It is established that while information about the mass of a black hole is not accessible from within the event horizon, observers outside can determine the mass based on the matter that fell into the black hole prior to its formation. The curvature of spacetime around the black hole serves as a record of this mass, contradicting the notion that the mass remains a secret.

PREREQUISITES
  • Understanding of general relativity
  • Familiarity with the "no hair theorem"
  • Knowledge of black hole properties: mass, charge, angular momentum
  • Concept of event horizons in black holes
NEXT STEPS
  • Research the implications of the "no hair theorem" in modern physics
  • Explore the relationship between black holes and spacetime curvature
  • Study the effects of black holes on surrounding celestial bodies
  • Investigate the conservation of information in black hole physics
USEFUL FOR

Astronomers, physicists, and students of astrophysics interested in the fundamental properties of black holes and their implications in the study of gravity and spacetime.

pitoko
Messages
2
Reaction score
0
The black hole is surrounded by an event horizon. No matter which fell under the horizon will never escape, even in the form of information (in the classical theory of relativity). So why is the star orbiting a black hole moving at the correct speed and trajectory, as if they knew the mass of a black hole? Knowledge of the mass of the black hole, depends on the amount of matter inside the event horizon, and this is a secret. How nature does it do?
 
Physics news on Phys.org
Hi pitoko, welcome to PF.

Black holes have charge, angular momentum, and mass. Look up "no hair theorem". It is not clear that the "no hair theorem" is always correct and so black holes may have some more hair, but they certainly have at a minimum the charge, angular momentum, and mass.
 
Any observer who was around before the black hole formed know how much mass went in, so the mass can't be secret. The curvature of spacetime surrounding the black hole is a frozen record of how much mass went in. Note that a person inside the event horizon can't use the mass of the black hole to send information to the outside; since the mass is conserved, it's not possible to modulate the signal.
 
Thank you for your answers DaleSpam and bcrowell, you answered me exactly what I wanted to know ;)
 

Similar threads

High School Is there a white hole inside every black hole?
  • · Replies 22 ·
Replies
22
Views
915
Undergrad You can't actually enter a blackhole?
  • · Replies 40 ·
2
Replies
40
Views
3K
Undergrad Supermassive black hole, surface gravity and tidal forces
  • · Replies 62 ·
3
Replies
62
Views
8K
Undergrad I don't see how a black hole's event horizon can be crossed
  • · Replies 73 ·
3
Replies
73
Views
2K
Undergrad Falling through the event horizon of an evaporating black hole
  • · Replies 51 ·
2
Replies
51
Views
5K
High School Theories about light and time near a black hole
  • · Replies 20 ·
Replies
20
Views
2K
High School Can Matter Enter a Black Hole Intact? Debate & Advice
  • · Replies 6 ·
Replies
6
Views
2K
High School Black Holes: How Do They Move?
  • · Replies 22 ·
Replies
22
Views
3K
Undergrad Inverse Square Law for Black Holes
  • · Replies 32 ·
2
Replies
32
Views
3K
Undergrad Escape from Two Black Holes? Solve the Mystery!
  • · Replies 2 ·
Replies
2
Views
2K