Density of an object in Relativity

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SUMMARY

The discussion centers on the concept of density in the context of special relativity, specifically addressing how relativistic mass affects density measurements. It is established that while relativistic mass increases with velocity, the rest mass remains constant and is independent of the observer's frame of reference. Consequently, phenomena such as rockets exploding due to increased density are not observed from the object's own frame. Density can only be accurately measured in a non-relative frame of reference, such as an accelerating frame.

PREREQUISITES
  • Understanding of special relativity principles
  • Knowledge of mass-energy equivalence
  • Familiarity with reference frames in physics
  • Basic concepts of density and pressure in materials
NEXT STEPS
  • Research the implications of relativistic mass in high-velocity scenarios
  • Explore the concept of rest mass versus relativistic mass
  • Study the effects of acceleration on measurements in different reference frames
  • Investigate materials' behavior under extreme pressure conditions in relativity
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Physicists, students of relativity, and anyone interested in the implications of relativistic effects on mass and density measurements.

gennarakis
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If the density of an object increases in special relativity (as mass increases and volume decreases), wouldn't we see strange phenomena as skyrockets exploding (because some materials can't sustain to much pressure)??
 
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It's only the "relativistic mass", which is similar to velocity in that it depends on your choice of reference frame, that increases...in the object's own frame its relativistic mass does not increase, and its "rest mass" (which is what physicists usually mean by 'mass') is not dependent on your choice of frame. So, the rocket won't explode or show any other odd behaviors which would be noticed by someone at rest relative to it, regardless of its velocity relative to us.
 
So the mass (and furthermore the density) can only be measured in a non relative frame of reference (as that of an accelerating one) otherwise you would never know the real mass of yours, hence the density.
 

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