Energy & Matter: Two different perspectives?

 
Speakpigeon
 
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Speakpigeon
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22 June 2018 09:55
 

If we compare the views from two different reference frames, in motion relatively to each other, at a constant velocity close to the speed of light, and one of them broadly at rest with respect to the entire universe, and the other one associated with an object having a small mass at rest. What are the differences in terms of total mass and total energy of the universe?
I would assume the overall rest masses to be identical. But from the frame broadly at rest, there’s just the one small object that’s near the speed of light. The energy involved is just the energy required to speed up the small object. No problem.
From the point of view of the frame associated with the small object, however, it’s the rest of the universe which is speeding up and with a velocity close to c. Where could the energy necessary to accelerate the entire universe possibly come from? And if we dismiss that perspective and say there’s no energy involved except the one necessary to accelerate the small object, then we also have to dismiss the relativistic mass of the rest of the universe seen as speeding at near the speed of light relatively to the frame of the small object.
This seems to suggest that relativistic mass is more a fiction than a reality.
Or where do I have it wrong?
EB

 
bbearren
 
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bbearren
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22 June 2018 11:34
 
Speakpigeon - 22 June 2018 09:55 AM

Or where do I have it wrong?

Between “If” and “reality”.  Since the universe is expanding (everything is moving away from everything rapidly), nothing can be “at rest with respect to the entire universe”.  Your basic premise is deeply flawed.

 
 
Speakpigeon
 
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Speakpigeon
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22 June 2018 12:10
 
bbearren - 22 June 2018 11:34 AM
Speakpigeon - 22 June 2018 09:55 AM

Or where do I have it wrong?

Between “If” and “reality”.  Since the universe is expanding (everything is moving away from everything rapidly), nothing can be “at rest with respect to the entire universe”.  Your basic premise is deeply flawed.

I fail to see how an expanding universe falsify my initial assumption of a barycentre, i.e. a centre of mass.
Further, as far as gravity is concerned, any nearby very large body would be a god approximation and could stand for the rest of the universe, say, the nearest galaxy.
If were talking in terms of relative speeds, it seems to me that in an expanding universe most areas of the universe are broadly at rest relative to the universe.
Or are you saying that none of all that Relativity stuff makes any sense?
The problem is not the problem. The problem is your attitude about the problem.
EB

 
bbearren
 
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bbearren
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22 June 2018 12:33
 
Speakpigeon - 22 June 2018 12:10 PM
bbearren - 22 June 2018 11:34 AM
Speakpigeon - 22 June 2018 09:55 AM

Or where do I have it wrong?

Between “If” and “reality”.  Since the universe is expanding (everything is moving away from everything rapidly), nothing can be “at rest with respect to the entire universe”.  Your basic premise is deeply flawed.

I fail to see how an expanding universe falsify my initial assumption of a barycentre, i.e. a centre of mass.

There is no “center of mass” for the universe; there is no “center” for the universe.

Further, as far as gravity is concerned, any nearby very large body would be a god approximation and could stand for the rest of the universe, say, the nearest galaxy.
If were talking in terms of relative speeds, it seems to me that in an expanding universe most areas of the universe are broadly at rest relative to the universe.

Nothing is at rest relative to anything else.  Everything is moving away from everything else.  The farther away a distant galaxy is from us, the faster it is moving away from us.  This is all well established cosmology, beginning with Hubble.

Or are you saying that none of all that Relativity stuff makes any sense?

No, I’m saying that it would appear that your understanding of it is lacking.

 
 
Speakpigeon
 
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Speakpigeon
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22 June 2018 12:54
 
bbearren - 22 June 2018 12:33 PM

There is no “center of mass” for the universe; there is no “center” for the universe.
Nothing is at rest relative to anything else.  Everything is moving away from everything else.  The farther away a distant galaxy is from us, the faster it is moving away from us.  This is all well established cosmology, beginning with Hubble.
No, I’m saying that it would appear that your understanding of it is lacking.

Thank you for this very relative contribution.
EB

 
Chaz
 
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Chaz
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14 July 2018 08:55
 

I like this one.

Speakpigeon - 22 June 2018 09:55 AM

If we compare the views from two different reference frames, in motion relatively to each other, at a constant velocity close to the speed of light, and one of them broadly at rest with respect to the entire universe, and the other one associated with an object having a small mass at rest. What are the differences in terms of total mass and total energy of the universe?

My understanding of the universe is different. The galaxies have mass and energy independent of each other, but the universe is infinite, so a “total” anything isn’t a possibility.

Speakpigeon - 22 June 2018 09:55 AM

I would assume the overall rest masses to be identical. But from the frame broadly at rest, there’s just the one small object that’s near the speed of light. The energy involved is just the energy required to speed up the small object. No problem.

Little bit of a problem for me. There wouldn’t be any energy required to speed up the object. When a star explodes, the energy from the blast would set the speed of what flies away, but that speed would remain constant as gravity being a force of equal pressure from all sides, which would neither slow down nor speed up the object.

Speakpigeon - 22 June 2018 09:55 AM

From the point of view of the frame associated with the small object, however, it’s the rest of the universe which is speeding up and with a velocity close to c. Where could the energy necessary to accelerate the entire universe possibly come from? And if we dismiss that perspective and say there’s no energy involved except the one necessary to accelerate the small object, then we also have to dismiss the relativistic mass of the rest of the universe seen as speeding at near the speed of light relatively to the frame of the small object.

This is a complete misunderstanding of epic proportions. The view from the small object wouldn’t require separate energy to explain anything. The energy causing it’s speed is the same energy causing it’s perspective.

Speakpigeon - 22 June 2018 09:55 AM

This seems to suggest that relativistic mass is more a fiction than a reality.
Or where do I have it wrong?
EB

I hope I helped a little with this. To clarify, the energy you’re asking about is gravity.

[ Edited: 14 July 2018 09:00 by Chaz]
 
Poldano
 
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Poldano
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29 July 2018 22:58
 

A third perspective is that the Big Bang was like the bursting of a bubble that is being inflated. Local particles accelerated toward local centers of mass, but the entirety kept on expanding at the rate it was going at the time it burst.