Infinite Mass, Infinite Energy

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The discussion centers on the concept of mass in the context of special relativity, particularly the idea that accelerating an object with rest mass to the speed of light (c) requires infinite energy. Participants debate whether the increase in mass is a real phenomenon or merely a perception based on the observer's frame of reference. They distinguish between invariant mass, which remains constant regardless of velocity, and relativistic mass, which varies with speed and is observer-dependent. The conversation also touches on the implications of time dilation and the nature of measurements in different inertial frames. Ultimately, the consensus is that while relativistic effects are real in the context of measurements, the notion of mass change is tied to the observer's perspective.
  • #31
There was an important question I asked that got overlooked.

With the increase of mass due to velocity, what is happening to density? Is the volume of the object increasing also?
 
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  • #32
WhyIsItSo said:
Is the volume of the object increasing also?

Remember length contraction? It applies in the direction parallel to the direction of motion, but the directions perpendicular to the motion are unaffected. So the volume of the object decreases.
 
  • #33
jtbell said:
Remember length contraction? It applies in the direction parallel to the direction of motion, but the directions perpendicular to the motion are unaffected. So the volume of the object decreases.
Huh...thinking...thinking...

mass increasing + volume decreasing = density increasing?

Or is this one of those points were relativity surprises me once again?
 

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