Is There a Minimum Energy Reference Frame?

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Discussion Overview

The discussion revolves around the concept of energy reference frames in the context of relativistic physics. Participants explore the implications of different observers measuring kinetic energy and momentum in varying reference frames, questioning whether a minimum energy reference frame exists.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the origin of energy as perceived by different observers, suggesting the possibility of a minimum energy reference frame.
  • Another participant asserts that in a system of inertially moving bodies in flat spacetime, total energy remains consistent across frames, implying no special frame exists.
  • A later reply emphasizes that kinetic energy is frame dependent and argues against the existence of a reference frame for minimum kinetic energy, except for the rest frame of the object where kinetic energy is zero.
  • One participant seeks clarification on whether a moving observer would experience Lorentz contraction of objects and the space between them, and raises the question of whether black holes could be frame dependent.
  • Another participant confirms the observation of Lorentz contraction for the moving observer.

Areas of Agreement / Disagreement

Participants express differing views on the existence of a minimum energy reference frame, with some arguing against it while others propose the idea. The discussion remains unresolved regarding the implications of relativistic energy and reference frames.

Contextual Notes

Participants acknowledge the frame dependence of kinetic energy and the need for further calculations to explore the implications of their arguments. There are unresolved questions about the nature of black holes and energy in different frames.

JustinRyan
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I have a small intuitive issue with the idea.

If you could humour me for a moment, imagine a particle moving at some velocity v.
An observer sitting on an armchair at rest wrt the background stars, but far enough away from them to negate any gravitational effects, sees the particle moving past at v and calulates it has an increase of momentum energy by virtue of its velocity wrt c.
A second observer, a microscopic cosmologist living on the particle (just humour me) looks through his telescope and sees the massive bodies (stars galaxies etc) all moving at relativistic velocities and he calculates that they have an astronomical amount of kinetic energy.
Where has that energy come from?
Would I be wrong to think that there is some reference frame of minimum energy?
 
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If you had a system of inertially moving bodies in flat spacetime, then the total energy of the system calculated from any frame will be the same. Otherwise there would be a 'special' frame. We have to use the relativistic definition of energy, which is invariant under Lorentz transformation.

I'm sticking my neck out because I haven't done a calculation, just a mental picture.

Edit : It is shown here* that the relativistic energy of a particle is invariant under Lorentz transformation. There is no preferred frame using this criterion.

*http://galileo.phys.virginia.edu/classes/252/energy_p_reln.html
 
Last edited:
JustinRyan said:
Where has that energy come from?
Would I be wrong to think that there is some reference frame of minimum energy?
Welcome to PF.

The energy hasn't come from anywhere. Kinetic energy is frame dependent. And yes, it is wrong to say that there is a reference frame for minimum kinetic energy...except of course, the rest frame of the object, where kinetic energy is zero.
 
So just so I am clear, my microscopic cosmologist will see a lorentz contraction of every object in space AND the space between them along the axis of his velocity?
I am going to have to do some more sums.
Could there be a case where he would witness a large mass + extra energy create a black hole? Can black holes be frame dependent?
 
JustinRyan said:
So just so I am clear, my microscopic cosmologist will see a lorentz contraction of every object in space AND the space between them along the axis of his velocity?
Yes.
 
Thanks. And thanks for the welcome :)
 

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