Measuring Mass of a Bowling Ball Dropped into a Black Hole

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SUMMARY

The discussion centers on the measurement of the mass of a bowling ball dropped into a black hole (BH) and the implications of relativistic effects on mass perception. It is established that while the astronaut holding the bowling ball measures its mass consistently, a distant observer can recover the rest mass of the ball as usable energy, yet sees no change in the mass of the BH once the ball is dropped. The conversation highlights the complexities of measuring mass in a relativistic context, particularly near the event horizon, and the differing perceptions of mass between observers in different frames of reference.

PREREQUISITES
  • Understanding of general relativity and black hole physics
  • Familiarity with the concept of event horizons
  • Knowledge of stress-energy tensors and their implications in curved spacetime
  • Basic principles of relativistic mass and energy equivalence
NEXT STEPS
  • Study the Schwarzschild metric and its implications for objects near black holes
  • Learn about the Rindler metric and its application to accelerating frames
  • Explore the concept of mass-energy equivalence in the context of general relativity
  • Investigate the role of stress-energy tensors in measuring mass in curved spacetime
USEFUL FOR

Physicists, astrophysicists, and students of general relativity interested in the effects of gravity on mass measurement and the behavior of objects near black holes.

  • #31
metastable said:
Does this not imply then that the "lowerer" will always be using more power in the experiment than is "gained" back via the tether?

So far we have been ignoring any power requirements for exerting thrust. This is typical for these kinds of thought experiments. :wink:

Since this thread is about how we would measure the mass of the object being lowered, not about whether any net energy can be extracted from the lowering process once the energy requirements for holding station are included, ignoring the power required to exert thrust for this thread does not seem objectionable. If you want to discuss the net energy extraction question, it would be fine to start a separate thread on that topic.
 
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  • #32
https://en.wikipedia.org/wiki/Ultimate_tensile_strength
I calculated a practical example. Make a 1 x 1 millimeter^2 thick tether of graphene and put it between the Moon and the surface of Earth.

Its mass is 380 metric tons, weight 60,000 Newtons, and it can lift a load of 7 tons from Earth.

The redshift from the surface of Earth is less than 10^-9. That is too small. We cannot measure the increase in the inertial mass of the 7 ton load.
 
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