Gravitational Time and Length Change, Looking for mass formula

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Discussion Overview

The discussion revolves around the concept of how mass may change in a gravitational field, drawing parallels to gravitational time dilation and length contraction. Participants explore the relationship between these phenomena and seek a formula that describes mass changes under gravity.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • One participant inquires about a formula for how mass changes in a gravitational field, suggesting a similarity to gravitational time dilation and length contraction.
  • Another participant asserts that mass does not change in a gravitational field, presenting a counterpoint to the initial inquiry.
  • A participant references an extreme scenario involving a 1 kg ball near a black hole, suggesting that while time appears to slow and the ball's size diminishes, its mass remains constant.
  • There is a request for clarification regarding the concept of "gravitational length contraction" and the formulas associated with it.
  • One participant speculates that since Planck time and Planck length are related by the speed of light, they might change in a similar manner, though this is not universally accepted.
  • Another participant challenges the notion of gravitational length contraction, asking for the basis of the claim and referencing the distinction between Planck units and the dimensions of physical objects.

Areas of Agreement / Disagreement

Participants express disagreement regarding the change of mass in a gravitational field, with some asserting it remains constant while others explore the possibility of change. The discussion remains unresolved with competing views on the relationship between mass, time, and length in gravitational contexts.

Contextual Notes

There are limitations in the discussion regarding the definitions of mass, time, and length, as well as the assumptions underlying the proposed relationships between these concepts. The references to Planck units and their applicability to macroscopic objects are also not fully clarified.

mcjosep
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Hi, Just curious if anyone knows of a formula that would show how mass changes in a gravitational field? I have seen the formulas for gravitational time dilation and length contraction (which are rather similar) and was wondering is mass changes the same way.

Thanks
 
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Mass does not change in a gravitational field.
 
mcjosep said:
I have seen the formulas for gravitational time dilation and length contraction (which are rather similar)

What formulas have you seen for "gravitational length contraction"?
 
Just to pick an extreme, a 1kg ball is a meter away from the event horizon of a black hole. So, to an outside observer, time is almost not moving at all for the 1 kg ball and its size has shrunk to almost a point due to gravitational length and time dilation but the ball would still be 1 kg?
 
PeterDonis said:
What formulas have you seen for "gravitational length contraction"?

hmm i just figured since Planck time and Planck length are related by a factor of c that they would change the same.
 
mcjosep said:
its size has shrunk to almost a point due to gravitational length

What are you basing this on? What formula? Do you have a reference?

mcjosep said:
i just figured since Planck time and Planck length are related by a factor of c that they would change the same.

The Planck time and Planck length are not the same as the length of an object or its proper time.
 

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