Does physics say my notion is incorrect?

[Markus Hanke]

5 hours ago, mistermack said:

What I was postulating was that, in any reference frame that you choose, (and stick to) accelerating expansion would at first sight mean increasing kinetic energy for nearly all of the matter in the Universe. 

Yes, and that’s no problem, because KE is a quantity that signifies a relationship between observer and the object (i.e. it’s relative, and not invariant); it’s not intrinsic to the distant object itself. 

5 hours ago, mistermack said:

That means massively increasing kinetic energy in that inertial frame, unless mass being converted to energy balanced that out. 

You don’t need to balance anything out, because there is no conservation law that needs to be satisfied in the first place.

[mistermack]

4 hours ago, Markus Hanke said:

Yes, and that’s no problem, because KE is a quantity that signifies a relationship between observer and the object (i.e. it’s relative, and not invariant); it’s not intrinsic to the distant object itself. 

I would say that it's a relationship between an inertial frame and the object. And if you look at it like that, then if you accelerate the object, you add kinetic energy. And you need REAL energy to do it. And, you have added the same quantity of energy, no matter which inertial frame you were considering. So the change in state seems to be particular to the object, rather than it's relationship to a particular inertial frame. So while the absolute quantity for KE is relative, any change in KE is not.

[Janus]

4 hours ago, mistermack said:

I would say that it's a relationship between an inertial frame and the object. And if you look at it like that, then if you accelerate the object, you add kinetic energy. And you need REAL energy to do it. And, you have added the same quantity of energy, no matter which inertial frame you were considering.

It is not true that you have added KE in every frame. There will be frames in which the the magnitude of the object's velocity has decreased after the acceleration ( the acceleration can be negative or positive depending on the frame) and thus it lost KE in that frame.  

Even the magnitude of the KE change is not constant across all frames. In the frame where a 1 Kg mass accelerates from 0 to 1m/s, it gains 0.5 joules of KE.  But in the frame where is is seen as accelerating from 1 m/s to 2 m/s,  it gains 1.5 joules of KE.

[mistermack]

1 hour ago, Janus said:

It is not true that you have added KE in every frame. There will be frames in which the the magnitude of the object's velocity has decreased after the acceleration ( the acceleration can be negative or positive depending on the frame) and thus it lost KE in that frame.  

Even the magnitude of the KE change is not constant across all frames. In the frame where a 1 Kg mass accelerates from 0 to 1m/s, it gains 0.5 joules of KE.  But in the frame where is is seen as accelerating from 1 m/s to 2 m/s,  it gains 1.5 joules of KE.

Yes, I knew there was something wrong with that straight after I wrote it, but wasn't sure what, so I thought it better not to edit it. I was thinking more about what happens up near the speed of light, when kinetic energy is increasing towards infinity. 

[swansont]

19 hours ago, mistermack said:

That's postulating a sudden change of reference frame. I'm certainly not advocating that. As you said, conservation requires keeping to the same reference frame. Jumping doesn't necessitate a change of frame.

Yes, it does.

19 hours ago, mistermack said:

In any case, I thought that in relativity, it was inertial motion that was relative, while acceleration is absolute. So when you jump, it's you that accelerates the most, and the Earth just a minescule amount. So you can't really postulate the Earth suddenly gaining enormous KE. 

Because energy is not an invariant.

19 hours ago, mistermack said:

What I was postulating was that, in any reference frame that you choose, (and stick to) accelerating expansion would at first sight mean increasing kinetic energy for nearly all of the matter in the Universe. 

But if you are also undergoing this expansion, as you would be from the point of view of a distant point, you have the same issue as jumping away from the earth.